It’s springtime which means sunshine, picnics and flies. But this episode might make you think twice about reaching for that fly swatter. Flies are amazing creatures that have the fastest visual systems in the world, use gyroscopes for precision flying, and can see almost 360 degrees.
- To understand why a fly is so unique, just look into their eyes.
- A fly has two large eyes that cover most of their head.
- Each eye consists of at least 3,000 individual lenses called ommatidia.
- With all of these “simple eyes” flies can’t focus on a single object like we do.
- Instead, they see the world as a kind of mosaic.
This makes them really good at spotting quick moving objects like a fly swatter. And their field of view is almost a full 360 degrees. So no use sneaking up from behind. Dr. Michael Dickinson is a bio-engineer and neuroscientist at Cal Tech and a leading expert on American flies.
On this episode he shares his love for flies and explains what makes them so special – from their eyes to their lightning fast neurological systems. So next time you might want to reach for that magnifying glass rather than the fly swatter – you’ll be amazed at what you see. Recommended links from Chris Morgan : Dickinson Lab Michael Dickinson: How a fly flies Understanding the neurological code behind how flies fly The Lab: Gwyneth Card + Escape Behavior THE WILD is a production of KUOW in Seattle in partnership with Chris Morgan and Wildlife Media.
It is produced by Matt Martin and edited by Jim Gates, It is hosted, produced and written by Chris Morgan. Fact checking by Apryle Craig, Our theme music is by Michael Parker,
- 1 How many eyes does a fly actually have?
- 2 Can flies feel pain?
- 3 How long can a fly remember?
- 4 Can flies fly in the dark?
- 5 Do flies respond to music?
- 6 Does a fly have 5 eyes?
- 7 Which fly has 5 eyes?
How many eyes does a fly actually have?
They have two prominent compound eyes composed of 3,000 to 6,000 tiny simple eyes (lenses) working together to make one visual masterpiece. A House fly also has three extra simple eyes centrally between the two prominent eyes. The three ocelli, as they are known, help a housefly navigate when flying.
Do flies have hearing?
Abstract – Studying the auditory system of the fruit fly can reveal how hearing works in mammals. Research Organism: D. melanogaster, Human, Mouse Related research article Li T, Giagtzoglou N, Eberl D, Nagarkar-Jaiswal S, Cai T, Godt D, Groves AK, Bellen HJ.2016. The myosin motor proteins play a variety of roles inside cells, such as transporting cargo around the cell and maintaining the structure of the cell’s internal skeleton. Myosins also make important contributions to our sense of hearing, which can be revealed by studying conditions such as Usher syndrome (a severe sensory disorder that causes congenital deafness and late-onset blindness).
- In humans and other mammals, two myosin proteins called myosin VIIa and myosin IIa have been linked to deafness, but we do not understand how these proteins interact.
- Now, in eLife, Andrew Groves, Hugo Bellen and co-workers – including Tongchao Li of Baylor College of Medicine as first author – report evidence of a conserved molecular machinery in the auditory organs of mammals and the fruit fly Drosophila ( Li et al., 2016 ).
Furthermore, the screen identified an enzyme called Ubr3 that regulates the interaction of the two myosins in Drosophila, Auditory organs convert the mechanical energy in sound waves into electrical signals that can be interpreted by the brain. In mammals, this conversion happens in “hair cells” in the inner ear.
These cells have thin protrusions called stereocilia on their surface, and the tips of these stereocilia contain ion channels called MET channels (which is short for mechanoelectrical transduction channels). Five proteins associated with the most serious form of Usher syndrome – known as USH1 – are key components of the molecular apparatus that enables the MET channels to open and close in response to mechanical force.
The USH1 proteins are restricted to the tips of the stereocilia, where they form a complex ( Figure 1 ; Prosser et al., 2008 ; Weil et al., 1995 ). Two of the USH1 proteins work together to join the tip of each stereocilium to its next-highest neighbor, forming bundles of stereocilia ( Kazmierczak et al., 2007 ). How sound is detected in mammals and Drosophila, ( A ) Schematic diagram showing a bundle of three stereocilia protruding from a mammalian hair cell. The deflection of the stereocilia by sound waves results in the opening of the MET channels (pale blue cylinders) and the generation of an electrical signal that travels along sensory neurons to the brain.
The motor protein myosin VIIa transports USH1 proteins to maintain the structural integrity of stereocilia. Figure adapted from Figure 1e, Richardson et al. ( Richardson et al., 2011 ). ( B ) Flies use antennae made up of three segments to detect sound. The schematic diagram on the left shows the second segment: there are MET channels for each neuron (outlined in green) and myosin II and myosin VIIa are enriched at the tip of scolopale cells, where USH1 proteins, Ubr3 and Cul1 form a protein complex.
A Pcdh15 protein in the USH1 complex anchors the tip of scolopale cell to the cap cell. When a sound wave hits the antenna, the joint between the second and the third segment is deflected (right panel) and the resultant stretching of the second segment opens the MET channels.
This depolarizes the sensory neurons, causing them to signal to the brain. Figure adapted from Figure 1b, Boekhoff-Falk and Eberl ( Boekhoff-Falk and Eberl, 2014 ). Flies do not have ears as such, but they are still able to detect sounds through their antennae. Despite the auditory organs of flies and mammals having different structures, they work in a similar way.
In Drosophila, structures called scolopidia, which are found suspended in the second segment of the antenna, sense sound vibrations relayed from the third segment ( Figure 1 ). Cells called cap cells and scolopale cells anchor the tip of the scolopidia to the joint between the second and third segments.
- The scolopale cells also secrete a protein to form the dendritic cap that connects a sensory neuron with the joint.
- This structure allows the mechanical forces produced by the sound waves to be transmitted to the neuron, activating the MET channels and causing the sensory neuron to produce an electrical signal.
Inactivating the gene that produces myosin VIIa causes the scolopidia to detach from the joint and causes the protein that forms the dendritic cap to be distributed abnormally ( Todi et al., 2005 ; Todi et al., 2008 ). Now, Li at al. – who are based at Baylor, the Texas Children’s Hospital, the University of Iowa and the University of Toronto – show that inactivating the gene that encodes the enzyme Ubr3 has the same effect.
Ubr3 is a type of E3 ubiquitin ligase. These enzymes regulate a number of cell processes by helping to join small proteins called ubiquitins onto other proteins. Using a forward genetic screen, Li et al. found that Ubr3 is enriched in the tips of scolopidia, particularly at the ends of the sensory neurons and in the scolopale cells closest to the joint between the second and third segments.
Li et al. show that Ubr3 and another E3 ubiquitin ligase called Cul1 negatively regulates the addition of a single ubiquitin to myosin II. This means that the loss of Ubr3 increases the rate of the “mono-ubiquitination” of myosin II, which leads to stronger interactions between myosin II and myosin VIIa.
Importantly, the mono-ubiquitination of myosin II and the interaction between myosin II and myosin VIIa helps to ensure that they (and also the fly equivalents of Usher proteins) localize correctly to the scolopidial tip. Thus, Ubr3 is crucial for maintaining the structure and function of scolopidia.
Overall, the results presented by Li et al. argue that a conserved model underlies hearing in both Drosophila and mammals. In this model, the negative regulation of mono-ubiquitination of myosin IIa (or myosin II in the case of Drosophila ) by Ubr3 promotes the formation of the myosin IIa-myosin VIIa complex (or the myosin II-myosin VIIa complex in Drosophila ).
The myosin complex then transports the USH1 protein complex to the tips of the stereocilia (or scolopidia) to establish the sound-sensing structure that enables the MET channels to work. Using the power of fly genetics, Li et al. have identified new components involved in the development and function of auditory organs, and linked them to genes known to play a role in human deafness.
Undoubtedly, future studies of these deafness-related genes in the Drosophila auditory organ will bring more insights into the interplay among the molecules, including the USH1 proteins, that are important for hearing.
Can flies feel pain?
Other pain indicators – The framework we used to evaluate evidence for pain in different insects was the one that recently led the UK government to recognise pain in two other major invertebrate groups, decapod crustaceans (including crabs, lobsters, and prawns) and cephalopods (including octopuses and squid), by including them in the Animal Welfare (Sentience) Act 2022.
- The framework has eight criteria, which assess whether an animal’s nervous system can support pain (such as brain-body communication), and whether its behaviour indicates pain (like motivational trade-offs).
- Flies and cockroaches satisfy six of the criteria.
- According to the framework, this amounts to “strong evidence” for pain.
Despite weaker evidence in other insects, many still show “substantial evidence” for pain. Bees, wasps, and ants fulfil four criteria, while butterflies, moths, crickets, and grasshoppers fulfil three. Beetles, the largest group of insects, only satisfy two criteria.
- But, like other insects that received low scores, there are very few studies on beetles in this context.
- We found no evidence of any insect failing all the criteria.
- Our findings matter because the evidence for pain in insects is roughly equivalent to evidence for pain in other animals which are already protected under UK law.
Octopuses, for example, show very strong evidence for pain (seven criteria). In response, the UK government included both octopuses and crabs in the Animal Welfare (Sentience) Act 2022, legally recognising their capacity for pain. The UK government set a precedent: strong evidence of pain warrants legal protection.
At least some insects meet this standard, so it is time to shield them. For starters, we recommend including insects under the Animal Welfare (Sentience) Act 2022, which would legally acknowledge their capacity to feel pain. But this law only requires the government to consider their welfare when drafting future legislation.
If we want to regulate practices such as farming and scientific research, the government needs to extend existing laws. For example, the Animal Welfare Act 2006, which makes it an offence to cause “unnecessary suffering” to animals covered by the act.
- This may lead to insect farms, like conventional farms, minimising animal suffering and using humane slaughter methods.
- The Animals (Scientific Procedures) Act 1986 regulates the use of protected animals in any experimental or other scientific procedure that may cause pain, suffering, distress or lasting harm to the animal.
Protecting insects under this act, as octopuses already are, would regulate insect research, reducing the number of insects tested and ensuring that experiments have a strong scientific rationale. Finally, pesticides are a huge welfare concern for wild insects.
Do flies have good memory?
Fruit Flies Can Learn, and Just Like Us, They Forget – Neuroscientists, scientists who study how the brain works, have been very interested in learning how memories are stored in the brain. However, neuroscientists have only very recently begun to study forgetting.
To understand how the human brain forgets, we can study how fruit flies forget. Fruit flies are awesome, small insects that are great for scientific research. They grow very fast in the laboratory and we can produce as many flies as we want. Their genetic material, or, is also very easy to change. DNA is a very long, thin chemical that contains the instructions to build any living organism.
DNA contains genes, which are sections of the DNA that tell a cell how to make a, The instructions contained in the DNA of the flies can be changed in the lab. Genes can be removed, making a mutant fly. In this way, we can explore what happens to a fly if a piece of these instructions is removed.
- Flies also have small brains that are much easier to explore than a human or mouse brain.
- Although you will find this surprising, human brains and fruit fly brains have many things in common.
- Amazingly, fruit flies can learn simple tasks, they can form memories, and they can also forget, just as we do.
Just like human brains, fly brains are made up mainly of cells called neurons. Neurons are the cells that transmit information across the brain. Groups of neurons, like a computer, can form circuits that process and store information. To study how flies forget, we first teach the flies a simple task.
- Then we give the flies a test to see how much they remember and how much they have forgotten.
- What do we teach them and how do we test their memory? Flies have a very powerful sense of smell.
- For this reason, we give the flies odors (or different smells) to learn.
- We first allow the flies to smell an odor and at the same time we give them a mild shock of electricity.
This causes the flies to learn that they will feel a bit of pain when they smell the odor. Then we test how much the flies remember by placing the flies in a tiny area with the odor that they smelled when they were shocked. If they remember well, the flies run away from the odor, thinking they will be shocked again—in this case, they score an A+ on this test.
Figure 1 Fruit flies can learn simple tasks, they form memories, and they can also forget. During the learning session, flies are allowed to smell an odor and at the same time they receive a mild shock of electricity. Flies learn that they will feel a bit of pain when they smell the odor. Then, memory is tested to see how much the flies remember by placing the flies in a tiny area with the odor that they smelled during the learning session. If they remember well, the flies run away from the odor and they score an A. If they have forgotten and do not run away from the odor, they score an F.
Using this simple experiment, we and other neuroscientists have found a new group of neurons in the fly brain that form a circuit in charge of making new memories. These neurons work together to learn and store a new memory. Once the memory is stored, these same neurons continue to work and this begins to slowly erase the memory that was just formed.
- If the new memories are not important, they will be gradually eliminated by the activity of this circuit, until they are completely erased,
- However, if the information learned is really important—like the location of a new source of food—or if the memory is recalled an hour or two later, then the memory will be “protected” from forgetting.
The neurons that cause forgetting use a brain molecule called, Interestingly, mutant flies that do not have one of the genes responsible for interpreting the dopamine signal, called dopamine receptor, remember the odor they have learned for a very long time.
- Basically, these flies have a long-lasting memory because they cannot forget.
- Another gene that is very important for forgetting unimportant memories is named Rac,
- The Rac gene makes a protein that speeds up changes to the skeleton of most cells.
- It is thought that changes in the skeleton of neurons are very important to create the structures that hold new memories.
Rac speeds up the chemical reactions that undo these changes in the skeleton and in doing so causes forgetting,
How long can a fly remember?
Insects have a spatial orientation memory that helps them remember the location of their destination if they are briefly deflected from their route. Researchers at Johannes Gutenberg University Mainz (JGU) have examined how this working memory functions on the biochemical level in the case of Drosophila melanogaster,
They have identified two gaseous messenger substances that play an important role in signal transmission in the nerve cells, i.e., nitric oxide and hydrogen sulfide. The short-term working memory is stored with the help of the messenger substances in a small group of ring-shaped neurons in the ellipsoid body in the central brain of Drosophila,
Flies form a memory of locations they are heading for. This memory is retained for approximately four seconds. This means that if a fly, for instance, deviates from its route for about a second, it can still return to its original direction of travel. “This recall function represents the key that enables us to investigate the biochemistry of working memory,” said Professor Roland Strauss of JGU’s Institute of Developmental Biology and Neurobiology.
- The researchers are particularly interested in learning how a network in an insect’s brain can build such an orientation memory and how exactly the related biochemical processes function.
- Working on her doctoral thesis, Dr.
- Sara Kuntz found to her surprise that there are two gaseous neurotransmitters that are involved in information transmission.
These gaseous messenger substances do not follow the normal route of signal transmission via the synaptic cleft but can diffuse directly across the membrane of neighboring nerve cells without docking to receptors. It was already known that, for the purposes of memory formation, nitric oxide (NO) is essential for the feedback of information between two nerve cells.
What has now emerged is that NO also acts as a secondary messenger substance in connection with the amplification of the output signals of neurons. This function of nitric oxide can apparently also be assumed by hydrogen sulfide (H2S). Although researchers were aware that this gas plays a role in the control of blood pressure, they had no idea that it had another function in the nervous system.
“It has long been assumed that hydrogen sulfide was harmful to the nervous system. But the results of our research show that it is also of importance as a secondary messenger substance,” explained Strauss. “We were absolutely astonished to discover that there are two gaseous neurotransmitters that are important to memory.” Biochemical signal transduction pathway for visual working memory Strauss and his colleagues postulate that both neurotransmitters together with cyclic guanosine monophosphate (cGMP) form the perfect storage media for short-term memories.
They presume the process functions as follows: The fruit fly sees an orientation point and moves in its direction, at which point nitric oxide is formed. The nitric oxide stimulates an enzyme that then synthesizes cGMP. Either the nitric oxide itself or cGMP accumulate in a segment of the doughnut-shaped ellipsoid body that corresponds to the original direction taken by the fly.
The ellipsoid body is located in the central complex of the insect brain and is divided into 16 segments, rather like slices of cake, each of which represents a particular spatial orientation. Given that a Drosophila fly deviates from its path because it loses sight of its initial orientation point and temporarily becomes aware of another, that fly is then able to get back on its original course because a relatively large quantity of NO or cGMP has accumulated in the corresponding ellipsoid body segment.
However, all of this only functions under one condition. The memory is only called up if the fly does not see anything in the interim, the fly must also lose sight of the second orientation point. “The recall function only becomes relevant when there is nothing more to see and readily acts as an orientation aid for periods of up to four seconds,” explained Dr.
Sara Kuntz, primary author of the study, adding that this seemingly short time span of four seconds is perfectly adequate to enable a fly to deal with such a problem. “The ellipsoid body retains the backup copy to span any such brief interruptions.” There is no point in having a working memory with a longer duration as objects that have been selected as orientation points are not necessarily anchored in place but may themselves also move.
Can flies fly in the dark?
Editor’s Note: The views expressed in this commentary are solely those of the writers. CNN is showcasing the work of The Conversation, a collaboration between journalists and academics to provide news analysis and commentary. The content is produced solely by The Conversation.
- The Conversation — Sitting outside on a summer evening always sounds relaxing until flies and mosquitoes arrive – then the swatting begins.
- Despite their minuscule eyes and a brain roughly 1 million times smaller than yours, flies can evade almost every swat.
- Flies can thank their fast, sophisticated eyesight and some neural quirks for their ability to escape swats with such speed and agility.
Our lab investigates insect flight and vision, with the goal of finding out how such tiny creatures can process visual information to perform challenging behaviors, such as escaping your swatter so quickly. Flies have compound eyes. Rather than collecting light through a single lens that makes the whole image – the strategy of human eyes – flies form images built from multiple facets, lots of individual lenses that focus incoming light onto clusters of photoreceptors, the light-sensing cells in their eyes.
Essentially, each facet produces an individual pixel of the fly’s vision. A fly’s world is fairly low resolution, because small heads can house only a limited number of facets – usually hundreds to thousands – and there is no easy way to sharpen their blurry vision up to the millions of pixels people effectively see.
But despite this coarse resolution, flies see and process fast movements very quickly. We can infer how animals perceive fast movement from how quickly their photoreceptors can process light. Humans discern a maximum of about 60 discrete flashes of light per second.
- Any faster usually appears as steady light.
- The ability to see discrete flashes depends on the lighting conditions and which part of the retina you use.
- Some LED lights, for example, emit discrete flashes of light quickly enough that they appear as steady light to humans – unless you turn your head.
- In your peripheral vision you may notice a flicker.
That’s because your peripheral vision processes light more quickly, but at a lower resolution, like fly vision. Remarkably, some flies can see as many as 250 flashes per second, around four times more flashes per second than people can perceive. If you took one of these flies to the cineplex, the smooth movie you watched made up of 24 frames per second would, to the fly, appear as a series of static images, like a slide show.
- But this fast vision allows it to react quickly to prey, obstacles, competitors and your attempts at swatting.
- Our research shows that flies in dim light lose some ability to see fast movements,
- This might sound like a good opportunity to swat them, but humans also lose their ability to see quick, sharp features in the dark.
So you may be just as handicapped as your target. When they do fly in the dark, flies and mosquitoes fly erratically, with twisty flight paths to escape swats. They can also rely on nonvisual cues, such as information from small hairs on their body that sense changes in the air currents when you move to strike.
- READ MORE: Flies really do regurgitate on your food But why do flies see more slowly in the dark? You may have noticed your own vision becoming sluggish and blurry in the dark, and much less colorful.
- The process is similar for insects.
- Low light means fewer photons, and just like cameras and telescopes, eyes depend on photons to make images.
But unlike a nice camera, which allows you to switch to a larger lens and gather more photons in dark settings, animals can’t swap out the optics of their eyes. Instead, they rely on summation, a neural strategy that adds together the inputs of neighboring pixels, or increases the time they sample photons, to form an image.
- Big pixels and longer exposures capture more photons, but at the cost of sharp images,
- Summation is equivalent to taking photographs with grainy film (higher ISO) or slow shutter speeds, which produce blurrier images, but avoid underexposing your subjects,
- Flies, especially small ones, can’t see quickly in the dark because, in a sense, they are waiting for enough photons to arrive until they are sure of what they are seeing.
READ MORE: The little-known high school teacher who revolutionized insect science In addition to perceiving looming threats rapidly, flies need to be able to fly away in a split second. This requires preparation for takeoff and quick flight maneuvers,
After visually detecting a looming threat, fruit flies, for example, adjust their posture in one-fifth of a second before takeoff. Predatory flies, such as killer flies, coordinate their legs, wings and halteres – dumbbell-shaped remnants of wings used for sensing in-air rotations – to catch their prey quickly midflight.
READ MORE: Wasps: why I love them, and why you should, too To outmaneuver a fly, you must strike faster than it can detect your approaching hand. With practice, you may improve at this, but flies have honed their escapes over hundreds of millions of years.
- So instead of swatting, using other ways to manage flies, such as installing fly traps and cleaning backyards, is a better bet.
- You can lure certain flies into a narrow neck bottle filled with apple cider vinegar and beer.
- Placing a funnel in the bottle neck makes it easy for them to enter but difficult to escape.
As for mosquitoes, some commercial repellents may work, but removing stagnant water around the house – in some plants, pots or any open containers – will help eliminate their egg-laying sites and reduce the number of mosquitoes around from the start.
- Avoid insecticides, as they also harm useful insects such as bees and butterflies.
- READ MORE: 4 reasons insects could be a diet staple, from zesty tree ants to peanut-buttery bogong moths Jamie Theobald is an associate professor of biological sciences at Florida International University.
- Ravindra Palavalli-Nettimi is a postdoctoral research associate at that university.
Theobald receives funding from the National Science Foundation. Palavalli-Nettimi does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond an academic appointment.
Do flies have feelings?
For decades, the idea that insects have feelings was considered a heretical joke – but as the evidence piles up, scientists are rapidly reconsidering. O One balmy autumn day in 2014, David Reynolds stood up to speak at an important meeting. It was taking place in Chicago City Hall – a venue so grand, it’s embellished with marble stairways, 75ft (23m) classical columns, and vaulted ceilings.
- As the person in charge of pest management in the city’s public buildings, among other things, Reynolds was there to discuss his annual budget.
- But soon after he began, an imposter appeared on one of the walls – a plump cockroach, with her glistening black body contrasting impressively with the white paint.
As she brazenly sauntered along, it was as if she was mocking him. “Commissioner, what is your annual budget for cockroach abatement?” one councillor interrupted, according to a report in The Chicago Tribune, Cue raucous laughter and a mad scramble to eradicate the six-legged prankster.
- No one would question the cockroach’s impeccable, though accidental, comic timing.
- But the incident is partly funny because we think of insects as robotic, with barely more emotional depth than lumps of rock.
- A cockroach that’s capable of being amused or playful – well, that’s just plain absurd.
- Or is it? In fact, there’s mounting evidence that insects can experience a remarkable range of feelings.
They can be literally buzzing with delight at pleasant surprises, or sink into depression when bad things happen that are out of their control, They can be optimistic, cynical, or frightened, and respond to pain just like any mammal would. And though no one has yet identified a nostalgic mosquito, mortified ant, or sardonic cockroach, the apparent complexity of their feelings is growing every year.
When Scott Waddell, professor of neurobiology at the University of Oxford, first started working on emotions in fruit flies, he had a favourite running joke – “that, you know, I wasn’t intending on studying ambition”, he says. Fast-forward to today, and the concept of go-getting insects is not so outrageous as it once was.
Waddell points out that some research has found that fruit flies do pay attention to what their peers are doing, and are able to learn from them, Meanwhile, the UK government recently recognised that their close evolutionary cousins – crabs and lobsters – as sentient, and proposed legislation that would ban people from boiling them alive. For insects, golden tortoise beetles are unusually good at making their feelings clear (Credit: Alamy) An evolutionary imperative Insects are a jumbled group of six-legged invertebrate creatures with segmented bodies. There are more than a million different types, encompassing dragonflies, moths, weevils, bees, crickets, silverfish, praying mantis, mayflies, butterflies, and even head lice.
The earliest insects emerged at least 400 million years ago, long before dinosaurs took their first tentative plods. It’s thought our last common ancestor with them was a slug-like creature which lived around 200 million years before that, and they’ve been diversifying ever since. Initially they ruled over the land as giants – some dragonflies were sparrowhawk-sized, with 2.3ft (70cm) wingspans – before evolving into the extraordinary array of arthropods around today, from flies with fake scorpion tails to fuzzy moths that resemble winged poodles,
As a result, they’re strikingly similar to other animals, and yet vividly different. Insects have many of the same organs as humans – with hearts, brains, intestines and ovaries or testicles – but lack lungs and stomachs. And instead of being hooked up to a network of blood vessels, the contents of their bodies float in a kind of soup, which delivers food and carries away waste.
The whole lot is then encased in a hard shell, the exoskeleton, which is made of chitin, the same material fungi use to build their bodies. The architecture of their brains follows a similar pattern. Insects don’t have the exact same brain regions as vertebrates, but they do have areas that perform similar functions.
For example, most learning and memory in insects relies on “mushroom bodies” – domed brain regions which have been compared to the cortex, the folded outer layer that’s largely responsible for human intelligence, including thought and consciousness.
(Tantalisingly, even insect larvae have mushroom bodies, and some of the neurons within them remain for their whole lives – so it’s been suggested that adult insects that went through this stage might be able to remember some things that happened before they metamorphosed.) There’s mounting evidence that our parallel neural setups power a number of shared cognitive abilities, too.
Bees can count up to four, Cockroaches have rich social lives, and form tribes that stick together and communicate. Ants can even pioneer new tools – they can select suitable objects from their environment and apply them to a task they’re trying to complete, like using sponges to carry honey back to their nest,
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However, though insect brains have evolved down an uncannily familiar path to our own, there is one crucial difference: while human ones are so engorged they sap 20% of our energy and drove women to evolve wider hips, insects have compacted their wits into packages several million times smaller – fruit flies have brains the size of a poppy seed, Asian honeybees scream with their bodies, by vibrating them (Credit: Alamy) So, even at first glance, it seems like insects would have the intellectual capacity for emotions. But does it make sense that they would have evolved them? Emotions are mental sensations that are usually linked to an animal’s circumstances – they’re a kind of mental programme that, when it’s set off, can change the way we act.
It’s thought that different emotions have emerged at different points in evolutionary history, but broadly they turned up to encourage us to behave in ways that will improve our ability to survive or reproduce, and ultimately, maximise our genetic legacy. Geraldine Wright, a professor of entomology at the University of Oxford, gives the example of hunger, which is a state of mind that helps you to alter your decision-making in a way that’s appropriate, such as prioritising food-seeking behaviours.
Other emotions can be equally motivating – rumblings of anger can focus our efforts on rectifying injustices, and constantly chasing happiness and contentment nudges us towards achievements that keep us alive. All these things could also apply to insects.
- An earwig that’s thrilled when it finds a nice damp crevice filled with delectable rotting vegetation will be less likely to starve or dry out, just as one that panics and plays dead when it’s disturbed has a better chance of escaping the jaws of a predator.
- Let’s say you’re a bee that ends up in a spider web, and a spider is swiftly coming towards your across the web,” says Lars Chittka, who leads a research group that studies bee cognition at Queen Mary, University of London.
“It’s not impossible that the escape responses are all triggered without any kind of emotions. But on the other hand, I find it hard to believe that this would happen without some form of fear,” he says. A heretical idea When Waddell first started his own research group in 2001, he had a fairly simple goal in mind. It’s difficult to study pain in fruit flies because they don’t respond to morphine. However, they are partial to cocaine (Credit: Alamy) To begin with, Waddell cautiously chose the word “motivation”, rather than “hunger”, to describe the flies’ state of mind – he suggested that they were more motivated to find food if it had been withheld.
- And people found it a little problematic,” says Waddell.
- Some other scientists felt that this was too anthropomorphic and preferred the term “internal states”.
- So I often had arguments that I thought were essentially meaningless, because they were just playing with that word,” he says.
- Then in a matter of years, studying insect intelligence became significantly more fashionable – and all of a sudden the term “motivation” was abandoned, with researchers making the case for insects having “emotional primitives”, says Waddell.
In other words, they experienced what looked suspiciously like emotions. “I had always thought of these physiological changes that occur when animals are in deprivation states – deprived of sex, deprived of food – as subjective feelings of ‘hunger’ and ‘sex drive’,” says Waddell.
- I’ve never really bothered labelling them as ’emotions’, pretty much because I thought it was going to get me into trouble.
- But before I knew it, everyone seemed to be more comfortable using that,” Now that the suggestion insects have feelings is slightly less scandalous, the field has exploded in popularity – and this strange group of animals is becoming more relatable by the day.
But proving that an insect can experience an emotion remains tricky. Take the humble bumblebee. In humans, those who have experienced trauma are especially wired to expect the worst – and this has also been demonstrated in a number of other vertebrate animals, including rats, sheep, dogs, cows, cod and starlings. Cockroaches are highly sociable and copy the behaviour of their peers, just like humans do (Credit: Alamy) First, the researchers trained a troupe of bees to associate one kind of smell with a sugary reward, and another with an unpleasant liquid spiked with quinine, the chemical that gives tonic water its bitter taste.
- Then the scientists divided their bee participants into two groups.
- One was vigorously shaken – a sensation bees hate, though it’s not actually harmful – to simulate an attack by a predator.
- The other bee crowd was just left to enjoy their sugary drink.
- To find out if these experiences had affected the bees’ mood, next Wright exposed them to brand new, ambiguous smells.
Those who had had a lovely day usually extended their mouthparts in expectation of receiving another snack, suggesting that they were expecting more of the same. But the bees who had been annoyed were less likely to react this way – they had become cynical.
- Intriguingly, the experiment also hinted that the bees weren’t experiencing some alien, unrelatable form of pessimism, but a feeling that might not be too dissimilar to our own.
- Just like humans who are feeling exasperated, their brains had lower levels of dopamine and serotonin.
- They also had lower levels of the insect hormone octopamine, which is thought to be involved in reward pathways.) Wright says many of the chemicals in our brains are highly conserved – they were invented hundreds of millions of years ago.
So an insect’s emotional experiences could be more familiar than you would think. “So from that perspective, yes, they may have diverged a little bit in terms of what they signal in which animal lineage, but it’s quite interesting,” she says. For example, Waddell’s research on fruit flies has found that their brains use dopamine just like ours do, to elicit feelings of reward and punishment.
- So it’s very, very interesting that those things have, you know, convergently evolved and are sort of similar,” says Wright.
- It means that that’s the best way of doing it.” Wright explains that her bee experiment doesn’t necessarily mean that all insects can experience pessimism or optimism, because bees are unusually social – community life at the hive is particularly cognitively demanding, so they’re considered intelligent for insects.
“But other insects probably do too,” she says. A clear message However, it would be surprising if insects could feel emotions but not express them at all. And tantalisingly, there are some hints that insects might be more relatable than you’d think here too. Industrial farming has turned much of the earth’s surface into a hostile environment for insects (Credit: Alamy) The problem is something Charles Darwin first considered in the late 19th Century. When he wasn’t pondering evolution or eating the “strange flesh” of the exotic fauna he discovered, he spent much of his time thinking about how animals communicate their feelings, and wrote up his findings in a little-known book.
In The Expression of the Emotions in Man and Animals, Darwin argues that – just like every other characteristic – the ways humans express their feelings would hardly have appeared out of nowhere in our own species. Instead, our facial expressions, actions and noises are likely to have evolved via a gradual process over millennia.
Crucially, this means that there’s probably some continuity among animals, in terms of the ways that we display our emotional state to others. For example, Darwin noted that animals often make loud noises when they’re excited. Among the loud chattering of storks and the threatening rattling of some snakes, he cites the “stridulations”, or loud vibrations, of many insects, which they make when they’re sexually aroused.
Darwin also observed that bees change their hums when they’re cross. This all suggests that you don’t need to have a voice box to express how you’re feeling. Take the golden tortoise beetle, which looks like a miniature tortoise that’s been dipped in molten gold. It’s not actually covered in the element, but instead achieves its glamorous look by reflecting light off fluid-filled grooves embedded in its shell.
However, pick one of these living jewels up – or stress it out in any way – and it will transform before your eyes, flushing ruby-red until it resembles a large iridescent ladybird. Most research on the beetle has focused on the physics of how it achieves the colour switch, but intriguingly, it’s thought that the response is controlled by the insect, which may choose to change depending on what’s going on around it – rather than something that just happens passively. Insects have diversified to fill almost every conceivable niche, but they all share similar brains – so emotions in insects may be universal (Credit: Alamy) Then there’s the Asian honey bee. Around October each year – during what’s ominously referred to as the “slaughter phase” – they run the gauntlet of gangs of bee-decapitating giant hornets, also aptly known as “murder hornets”.
The wasps have a wide native range in Asia, from India to Japan, but scientists suspect they’re slowly invading other areas, with occasional sightings in North America, Their raids on bee hives can last for hours, and wipe out entire colonies – first, they cut up their worker bee victims into pieces, then they go for their offspring.
But the bees don’t go quietly. In work released earlier this year, scientists revealed that they scream – using an amplified, frantic version of their usual buzz. And though no one has conclusively tied the shrieks to an emotional response in the bees, the study’s authors noted in their paper that these “antipredator pipes” share similar acoustic features to the alarm calls of many other animals, from primates to birds to meercats, and might suggest that they’re fearful.
A n uncomfortable truth However, the most contentious aspect of the inner lives of insects has to be pain. “There’s lots of evidence in fruit fly larvae that they feel mechanical pain – if we pinch them, they try to escape – and the same is the case for adult flies as well,” says Greg Neely, a professor of functional genomics at the University of Sydney.
As always, proving that these unpleasant experiences are interpreted as emotional pain is another matter. “The issue is really the higher order aspect,” says Neely. However, there’s emerging evidence that they can indeed feel pain as we know it – and not only that, they can experience it chronically, just like humans.
- One basic clue to the former is that, if you train fruit flies to associate a certain smell with something unpleasant, they will simply run away whenever you present them with it.
- They link together the sensory context with the negative stimulus, and they don’t want that – and so they go away from it,” says Neely.
When fruit flies are prevented from escaping, they eventually give up and exhibit helpless behaviour that looks a lot like depression. But perhaps the most surprising results have emerged from Neely’s own research, which has found that injured fruit flies can experience lingering pain, long after their physical wounds have healed. Insect populations are declining accross the whole planet (Credit: Alamy) And though pain hasn’t yet been studied in a wide variety of insects, Neely thinks its likely that it would be similar across the board. “If we look at the overall architecture of how the brain is set up – the receptors, the ion channels and the neurotransmitters are all pretty similar,” says Neely, who points out that you can find examples of insects that are blind to these sensory signals, such as larvae that are in the middle of their transition to adulthood, but this is unusual.
A question of numbers All this research has some unsettling implications. At the moment, insects are among the most persecuted animals on the planet, routinely killed in almost-incomprehensibly large numbers. This includes 3.5 quadrillion – 3,500,000,000,000,000 – poisoned by insecticides on US farmland each year, two trillion squashed or slammed by cars on Dutch roads, and many more that have gone uncounted.
But though there isn’t much data on the full extent of our insecticide, one thing is widely accepted – the numbers we’re despatching are so vast, we’re living through an “insect Armageddon”, an era where insects are vanishing from the wild at an alarming rate. During “slaughter season” gangs of giant Asian hornets launch ferocious attacks on honeybees, decapitating the adults and eating their offspring (Credit: Alamy) The discovery of insect emotions also poses a slightly awkward dilemma for researchers – especially those who have devoted their careers to uncovering them.
Fruit flies are the archetypal research animal, studied so intensively that researchers know more about them than almost any other. At the time of writing, there are around 762,000 scientific papers that mention its Latin name, ” Drosophila melanogaster “, on Google scholar. Equally, studies into bees are growing in popularity, for the insights they can provide into everything from epigenetics – the study of how the environment can influence the way our genes are expressed – to learning and memory,
Both have endured more than their fair share of experimentation. “I like to watch bees and I’ve studied behaviour for a lot of my career, so I empathise quite a lot with them already,” says Wright, who has been a vegetarian for decades. However, the numbers used in research are tiny compared to those sacrificed elsewhere, so she feels that it’s easier to justify.
“It’s this sort of disregard of life in general that we have – you know, people just wantonly take life and destroy it and manipulate it from humans to mammals, insects to plants.” But while using insects for research is still largely uncontroversial, the discovery that they may think and feel raises a number of sticky conundrums for other fields.
There’s already a historical precedent for banning pesticides to protect certain insects – such as the EU-wide embargo on nicotinoids for the sake of bees. Could there be scope for moving away from others? And though insects are increasingly promoted as a noble and environmentally friendly alternative to meat from vertebrates, is this actually an ethical win? After all, you’d have to kill 975,225 grasshoppers to get the same volume of meat as you would from a single cow.
- Perhaps one reason we don’t tend to think of insects as emotional is that it would be overwhelming.
- Zaria Gorvett is a senior journalist for BBC Future and tweets @ZariaGorvett – Join one million Future fans by liking us on Facebook, or follow us on Twitter or Instagram,
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Can flies hear human voices?
What We Can Learn From A Fly’s Ears This may come as a surprise to you, but most flies don’t have the ability to hear. However, certain parasitic flies have a hearing system that is so exact in pinpointing a sound’s origin that it rivals the exceptional ears of owls and cats. This fly’s superb hearing surprised scientists because its tiny body is too small to use the same kind of hearing system that larger animals use.
- And yet they discovered that the fly was using its hearing to locate the chirps of crickets in order to then deposit parasitic larvae onto the crickets’ bodies.
- What they found was unlike any other known ear structure, this fly’s eardrums are connected by a bridge of stiff material.
- Vibrations that travel between the two eardrums enable the fly to pinpoint the origin of a sound as accurately as any other sound system we know of.
And what’s more, this fly’s exceptional hearing system is influencing microphone and hearing aid technology. For instance, it could lead to hearing aids that hide within a person’s ear canal and yet are able to gather sound primarily from the direction the listener is facing.
Do flies respond to music?
A fly’s hearing If your attendance at too many rock concerts has impaired your hearing, listen up. University of Iowa researchers say that the common fruit fly, Drosophila melanogaster, is an ideal model to study hearing loss in humans caused by loud noise.
- The reason: The molecular underpinnings to its hearing are roughly the same as with people.
- As a result, scientists may choose to use the fruit fly to quicken the pace of research into the cause of noise-induced hearing loss and potential treatment for the condition, according to a paper published this week in the online Early Edition of the journal Proceedings of the National Academy of Sciences,
“As far as we know, this is the first time anyone has used an insect system as a model for NIHL (noise-induced hearing loss),” says Daniel Eberl, UI biology professor and corresponding author on the study. Hearing loss caused by loud noise encountered in an occupational or recreational setting is an expensive and growing health problem, as young people use ear buds to listen to loud music and especially as the aging Baby Boomer generation enters retirement.
Despite this trend, “the molecular and physiological models involved in the problem or the recovery are not fully understood,” Eberl notes. Enter the fruit fly as an unlikely proxy for researchers to learn more about how loud noises can damage the human ear. Eberl and Kevin Christie, lead author on the paper and a post-doctoral researcher in biology, say they were motivated by the prospect of finding a model that may hasten the day when medical researchers can fully understand the factors involved in noise-induced hearing loss and how to alleviate the problem.
The study arose from a pilot project conducted by UI undergraduate student Wes Smith, in Eberl’s lab. “The fruit fly model is superior to other models in genetic flexibility, cost, and ease of testing,” Christie says. The fly uses its antenna as its ear, which resonates in response to courtship songs generated by wing vibration.
- The researchers exposed a test group of flies to a loud, 120 decibel tone that lies in the center of a fruit fly’s range of sounds it can hear.
- This over-stimulated their auditory system, similar to exposure at a rock concert or to a jack hammer.
- Later, the flies’ hearing was tested by playing a series of song pulses at a naturalistic volume, and measuring the physiological response by inserting tiny electrodes into their antennae.
The fruit flies receiving the loud tone were found to have their hearing impaired relative to the control group. When the flies were tested again a week later, those exposed to noise had recovered normal hearing levels. In addition, when the structure of the flies’ ears was examined in detail, the researchers discovered that nerve cells of the noise-rattled flies showed signs that they had been exposed to stress, including altered shapes of the mitochondria, which are responsible for generating most of a cell’s energy supply.
Flies with a mutation making them susceptible to stress not only showed more severe reductions in hearing ability and more prominent changes in mitochondria shape, they still had deficits in hearing 7 days later, when normal flies had recovered. The effect on the molecular underpinnings of the fruit fly’s ear are the same as experienced by humans, making the tests generally applicable to people, the researchers note.
“We found that fruit flies exhibit acoustic trauma effects resembling those found in vertebrates, including inducing metabolic stress in sensory cells,” Eberl says. “Our report is the first to report noise trauma in Drosophila and is a foundation for studying molecular and genetic conditions resulting from NIHL.” “We hope eventually to use the system to look at how genetic pathways change in response to NIHL.
Also, we would like to learn how the modification of genetic pathways might reduce the effects of noise trauma,” Christie adds. Eberl’s and Christie’s UI Department of Biology colleagues are: Elena Sivan-Loukianova, Wesley C. Smith (currently at UCLA), Benjamin T. Aldrich, Michael A. Schon, Madhuparna Roy (currently at the University of Pittsburgh), and Bridget C.
Lear. The research was supported by the National Institutes of Health (grant number R21 DC011397) to Eberl and P30 DC10362 to Steven Green), in support of the Iowa Center for Molecular Auditory Neuroscience. : A fly’s hearing
Do flies have brains?
Abstract – Studying neurons and their connections in the central complex of the fruit fly reveals new insights into how their structure and function shape perception and behavior. Research organism: D. melanogaster Related research article Hulse BK, Haberkern H, Franconville R, Turner-Evans DB, Takemura S, Wolff T, Noorman M, Dreher M, Dan C, Parekh R, Hermundstad AM, Rubin GM, Jayaraman V.2021.
- A connectome of the Drosophila central complex reveals network motifs suitable for flexible navigation and context-dependent action selection.
- ELife 10 :e66039.
- Doi: 10.7554/eLife.66039 You may have never heard of or flipped through the pages of ‘Atlas of an Insect Brain’.
- Published in 1976, this book is notoriously difficult to obtain as a paper copy ( Strausfeld, 1976 ).
But if you ever had the chance of marveling at the large, richly colored images that meet the eye page after page, you have certainly never looked at an ordinary housefly the same way again. In unprecedented detail, this book illustrated the complexity of the insect brain.
From sensory processing centers all the way to higherorder brain regions, the book recapitulated the intricate neural projection patterns that have evolved to control the fly’s interactions with the outside world. The stunning images were all based on the classic technique of Golgi silver impregnation and the random labelling of single neurons that is typical for this method.
By combining thousands of single neuron drawings, the internal layout of most parts of the insect brain was revealed for the first time, alongside the immense complexity and versatility of the individual neurons that comprise it. One area of the fly brain stood out with an arrangement of neural fibers orchestrated into an almost crystalline regularity.
- This region, the central complex, is the only unpaired part of the insect brain and is one of its highest-level processing centers ( Pfeiffer and Homberg, 2014 ).
- The highly ordered projection patterns of its neurons have been intensely studied over the last decades, and insights into the functional significance of this layout have emerged ( Heinze and Homberg, 2007 ; Honkanen et al., 2019 ; Turner-Evans et al., 2017 ).
These revelations have placed the central complex at the interface of sensory processing and behavioral control, where information about the world is transformed into decisions about what to do next. To ensure that the correct behaviors are carried out in the correct context, the central complex also controls internal states, such as sleep, and it has also been implicated in memory, in particular visual place memory ( Donlea et al., 2018 ; Ofstad et al., 2011 ).
- These multiple roles comprise all the processes that might be described as the core functions of brains in general, resulting in the description of the central complex as the ‘brain in the brain’ ( Strausfeld, 2012 ).
- Combined with the fact that it is evolutionarily as old as insects themselves, these fundamental roles have made the central complex the target of hundreds of studies, not only in flies, but across many insect species.
Yet, a central question has remained: how does the circuitry of the central complex enable all these different functions? Now, in eLife, Vivek Jayaraman and colleagues – including Brad Hulse, Hannah Haberkern, Romain Franconville and Daniel Turner-Evans as joint first authors – report new answers to this question ( Hulse et al., 2021 ).
Like the ‘Atlas of an Insect Brain’ at its time, this paper is the culmination of a massive, unprecedented effort, containing over 200 pages and nearly 80 figures. There is no doubt that it will be equally transformative to the field. The researchers, based at Janelia Research Campus, mapped the neural connections of all neurons of the Drosophila central complex: that is, they constructed a full connectome of this enigmatic brain area ( Figure 1 ).
This was done in multiple steps that first involved obtaining many terabytes of high-resolution images from one single fly brain by serial section electron microscopy. Via machine learning algorithms, each pixel in these images was then assigned a neuronal identity, yielding a dataset of many thousands of neurons that filled the imaged volume (see also Scheffer et al., 2020 ). The connectome of the central complex of a fruit fly. Using electron microscopy, the brain of the fruit fly ( Drosophila melanogaster, head depicted on the left) was imaged at high resolution. All neurons of the central complex were reconstructed (some of which are shown in the middle image) and their synaptic connections were extracted.
The resulting neuronal networks (symbolically illustrated on the right) were linked to the functions they have in controlling the fly’s behavior. They first analyzed the parallel input pathways that supply the central complex with information about the external world and about self-motion. The neurons involved are connected to a circuit that is known to encode the direction the head is pointed at ( Hulse and Jayaraman, 2020 ).
The connectome allowed Hulse et al. to validate existing concepts about how flies keep track of their orientation, and to recapitulate which inputs have the strongest impact on the fly’s perception of its heading in space. It also revealed how the associated neural signals progress through the circuits within the central complex, and how information about head direction is slowly transformed into an activity pattern useful to guide movements.
While the head direction circuit had been exceptionally well described before, the work of Hulse et al. also shed light on a number of previously elusive regions, in particular the fan-shaped body (which is the largest and most complex part of the central complex). By carefully analyzing the intrinsic connectivity patterns, the researchers distilled a handful of network motifs, suited to perform defined neural computations.
The fly could use these, for example, to transform its signal about head direction into a representation of traveling trajectory, or to encode goal directions to guide it during foraging. To compute goals that are relevant in any given situation, the central complex needs to also incorporate input from previous experience and its internal state.
- Such context-providing input was found to reach the fan-shaped body from numerous brain areas, including the main memory centers, the mushroom bodies.
- These inputs meet the various populations of neurons within the central complex and set up a system in which the state-encoding neurons could act as gatekeepers that control which activity patterns can reach output neurons, which, in turn, initiate appropriate steering commands or other actions.
While many of the specific concepts developed by Hulse et al. need to be confirmed by functional data, broader insights also emerged. First, the neuroanatomy of the central complex is indeed key to understanding its computations. The systematic projection patterns of its neurons, already visible in ‘Atlas of an Insect Brian’, are the dedicated hardware that generates context dependent behavior in response to sensory information.
- Second, the complexity of the connections in the central complex is far greater than anticipated from models and functional data.
- The connectome identified many apparent redundancies, connections that almost always allow information to flow in both directions, and many more neuron types being connected to one another than expected.
The connectome on its own therefore adds enormous amounts of complexity to the pool of available data. However, to enable us to understand which connections are important for which aspects of fly behavior, it will be essential to ground these data in functional observations.
At the same time, the connectome itself is the basis for new hypotheses about circuit function. With the deep level of understanding spearheaded by Hulse et al., we will gain impressive amounts of knowledge about the neural control of fly behavior. But how many of the identified circuits exist only in flies? That is, how much of the insights can we generalize from the D.
melanogaster connectome to other insects, or even to animal brains in general? This is impossible to say without looking at other species at a similar level of detail. Hulse et al. have provided a roadmap for how to carry out such a task with unparalleled scrutiny, and, importantly, they have provided the ground truth that can be used to benchmark all future work on this topic.
Does a fly have 5 eyes?
The Fly’s Head While you might think that the fly has two large eyes, it actually has five eyes. The two that we can see are its compound eyes. Then, there are three smaller eyes on the top of the head. The smaller eyes are called ocelli and while the compound eyes are complex, the ocelli simply process movement.
Which fly has 5 eyes?
Bees have 5 eyes.
Which animal has 8 eyes flying?
Spiders are animals that usually have eight eyes. Explanation : Spiders are arthropods that are known for their eight legs and for spinning webs to catch their prey. Many species of spiders have eight eyes, which are typically arranged in two rows of four,
- The eyes of a spider can detect light and movement, and some species have eyes that are highly developed and can see in colour.
- Spiders use their eyes to locate prey, avoid predators, and navigate their environment,
- The number and arrangement of a spider’s eyes can vary depending on the species, and some spiders have eyes that are highly specialized for certain tasks.
For example, some spiders have eyes that are sensitive to ultraviolet light, which helps them locate flowers and other sources of food, Spiders are found in almost every corner of the globe and can be found in a wide range of habitats, including forests, deserts, and grasslands.