Insect behavior is influenced by a number of factors: day light, temperature, time, other species they interact with… Understanding the importance of each of these factors is crucial for predicting how these little animals acclimatize and adapt, particularly in a context of climate change. It happens that many ecological services depend on activities of theirs, like pollination. But studying the behavior of insects in their natural habitat is extremely complex. Fortunately, the Great Vivarium at the Insectarium, which reproduces a tropical climate with controlled temperature and humidity, constitutes an ideal environment for the study of insects.
At what time do butterflies feed?
For this first study carried out in the Great Vivarium, we focused on butterflies’ feeding. At different times during the day and over several days, we noted the activity of 24 butterfly species: were they just resting on a leaf, or were they instead occupied with drinking the nectar from a flower? We also measured variables likely to affect insect behavior, like the temperature in the Great Vivarium, and cloud cover. Our first finding: butterflies feed mainly around noon!
What regulates butterfly activity?
This behavior observed in butterflies may be owing to different factors. For example, butterflies may feed when the temperature is ideal or when they sense that the Sun is at its zenith. Another hypothesis is that their internal clock may dictate their timetable for the day.
By way of statistical analyses, we were able to show that butterflies gathered nectar around noon, regardless of the temperature and the presence or not of the Sun. So our study corroborates the theory according to which butterflies have an internal clock that regulates their circadian rhythm, in other words their daily biological cycle. And that clock is very old, since it can be observed in butterflies from different families and from different parts of the world.
Why do butterflies have a circadian rhythm?
It’s hard to know why butterflies have a circadian rhythm. Nevertheless, we can formulate new hypotheses. For instance, the production and quality of nectar may be higher around noon, which would make the flowers more attractive for nectarivorous insects. All of them feeding at the same time may also reduce the risk of being gobbled up by a predator: a single butterfly has a good chance of being eaten, whereas a butterfly together with another one has one chance in two, and so on. The avenues to explore are interesting – but more research will be needed to determine the answers.
A museum and a laboratory
Besides being a section of the Insectarium that visitors very much enjoy, the Great Vivarium also benefits scientists. As we saw with this first experiment on butterfly feeding, this great laboratory has the potential to be an interesting place for research. Stay tuned to find out the results of the other projects we’re conducting in our experimental tropical forest!