Written by Joe Ballenger
After our spider post, I thought it would be nice to tackle this question because these questions open one of the biggest rabbit holes in the field of insect science:
Since you are the experts, my question is this: Since some species of birds are more bold (or smarter?) than others, is it possible for insects (if a mantis is in that classification) to be bold or shy also? Especially since they are mostly at the bottom of the food chain for a lot of species further up that chain, I would have expected the mantis to abandon his perch at my approach.
Hmm! Glad nobody saw that or I’d be labeled the Mantis Whisperer!
This person is essentially asking whether different individual insects within a species display different behaviors. Put another way, do insects have personalities?
The short answer is yes, for a reason that’s almost anticlimatic.
That being said, insects are being used to tackle some fascinating questions about the role of nature, nurture, development and genetics in describing personality.
Personality is pretty easy to define and measure. Personality is a set of individual differences in behavior. In other words, if you take two individuals from the same species…will they act differently in similar situations?
There’s a lot of good evidence for personality in insects that’s very well understood. Honeybee colonies, for example, can become very aggressive if genes from the African strains get introduced by accident. In a similar vein, workers become more aggressive as they age…and different workers can be more or less aggressive.
Entomologists who work with individual insect colonies can also tell you that different colonies will act differently. When working with paper wasps, some colonies are more defensive than others. Some will happily let you handle them after they become accustomed to captivity, whereas others never get used to the idea of Godzilla cleaning out their cage and attack. In the wild, I’ve both been attacked by paper wasp colonies and had others land on my head (between my eyes, no less!) after disturbing their nest.
The literature is kind of a mixed bag on this. Some papers are good, but others use analysis which are far too complicated for the question they’re trying to answer. However, although you can expect similar behaviors within a species, it’s generally accepted that there will be some variation in how extreme different behaviors are…which is how personality is defined.
In nature, everything is variable…and personality is defined by variability. Anticlimatic, I know…but sometimes that’s how things shake out.
Nature, Nuture, and Chance
One of the papers I linked to earlier, one with aphids, looked at their escape behaviors…and different individuals were found to be variable in how eagerly they dived off leaves to escape predators. Aphids are all clones, so this can’t be genetic. It was also the first time they’d encountered a predator, so it’s not a learned behavior.
When discussing personality there’s always the question of nature (e.g. genetics), versus nurture (learned behavior). This fits into something different. It’s a behavior that’s not genetic, but also not learned. It’s not nature as we typically think about it, but also not nurture.
So what’s going on?
Unfortunately, aphids are not the best model to answer this question with.
Drosophila is a small fly that’s freakishly easy to work with. It’s very small, which makes it challenging for some studies, but it can use all our genetic tools. A lot of laboratory strains are highly inbred, to the point where they’re essentially clones of one another. This is done to make everything as standardized as possible in genetic experiments, so we can (almost) eliminate different genetics as long as everybody’s raised on the same diet and fed the same food.
These flies also have behaviors which are very predictable. If you scare them, they skitter towards light most of the time. Roughly 60-80% of the time, depending on the genetic background.
Most of the time, but not all of the time. Within the inbred lines, they noticed that some flies went towards the light each and every time without fail. They tried to breed the behavior out, but the behavior wasn’t inherited. The behavior also appeared in insects raised without light, and in an unrelated species. The only strains which didn’t show this sort of variability were flies bred to be blind.
So here you have a distinct personality…individual flies which are different from their almost genetically identical peers. Their behavior isn’t inherited. It happens in flies which can see, but which have never seen light. It happens in other species which aren’t closely related to flies. However, the behavior isn’t seen in flies which are blind.
Specific genes seem to be involved, including one which shuttles in chemicals which are needed to make neurotransmitters. The gene White codes for a sort of pump which brings tryptophan into cells. In addition to being essential to make the pigments which gives fly eyes their colors, tryptophan is needed to make chemicals which send signals in the brain.
Flies with a broken White gene skitter towards light about as often as you’d expect…there’s much less variability. Everybody goes towards the light the standard 60-80% of the time, and nobody goes towards the light every single time.
Impairing White also impairs vision, but messing up different genes which result in vision impairment don’t seem to extinguish the personality. So this seems to be specific to White.
While impairing White disables the personality, feeding the flies chemicals needed to make neurotransmitters seems to restore the ability of the flies with the impaired copy of White to have this personality. Even when vision is impaired by a defective White gene, the flies regain the personality when fed chemicals which they can convert to serotonin.
So we know some flies have personalities, and it seems like every individual fly’s brain wires itself slightly differently during development even when they’re genetically identical. While their behaviors are expected to be similar because of background genetics, it seems that you can’t expect development to play out the same way each and every time.
The Bottom Line
There is a lot we don’t know about insect neuroscience. There’s a lot we don’t know. In fact, we hardly know anything when we compare them to what we know about people.
However, we do know that insects are very complicated. We know they can learn. We know they can communicate between one another. They respond to stimulus in ways which aren’t always predictable. Different individuals have personality.
The story of insect White and the light-seeking personality trait is important because it demonstrates that the biological determinants of behavior are far more complicated than genetics. Development is also important, and there are subtle differences between individuals which aren’t captured in the genome.
At the beginning of this post, I said this topic was a bit of a rabbit hole. A few weeks ago, we tackled a neat question about how spiders communicate. This week, we tackled the question of whether insects have personalities.
One of the most common-and controversial-questions entomologists get is whether insects are like people in terms of how they behave. We know there’s similarities, in terms of personality and communication, but a lot of people frequently ask whether insects are conscious and feel pain. I don’t feel like answering these questions would be complete without tackling these topics.
So that’s what I’m going to cover in an upcoming post: Are insects conscious, and do they feel pain?
- Kain, J. S., Stokes, C., & de Bivort, B. L. (2012). Phototactic personality in fruit flies and its suppression by serotonin and white. Proceedings of the National Academy of Sciences, 109(48), 19834-19839.
- Kralj-Fišer, S., & Schuett, W. (2014). Studying personality variation in invertebrates: why bother?. Animal Behaviour, 91, 41-52.
- Schuett, W., Dall, S. R., Baeumer, J., Kloesener, M. H., Nakagawa, S., Beinlich, F., & Eggers, T. (2011). Personality variation in a clonal insect: the pea aphid, Acyrthosiphon pisum. Developmental psychobiology, 53(6), 631-640.