Butterfly Show: Ask an Expert

While it is possible that some pollinators are aggressive towards each other, I am amazed at how often I see the opposite: butterflies, bees, wasps and other pollinators “getting along” together on nectar sources. One exception to that is the native solitary bees that have territorial males, which can be aggressive in a sort of cute way. I’ve seen them try to bonk a bumblebee off a flower. However, most large wasps have little incentive to be aggressive at flowers. Wasps are mainly meat eaters, either as predators or parasitoids. When we see them at flowers, they are mostly stopping to re-fuel so that they have the energy to search for caterpillars, spiders and other soft-bodied insects. Although the wasps that live in large nests will aggressively defend the nest, there isn’t much reason for them to be aggressive towards other insects, such as butterflies, at flowers. However, it is possible that their huge appetite for caterpillars might be having an impact on the numbers of butterflies in your yard.

Another reason for the decline that you observed is that butterfly numbers can fluctuate greatly from one year to the next. Some years are better than others for monarchs (I wasn’t sure if you were seeing a decline in the numbers of this particular species or if it was a dip in the numbers of butterflies in general you had noticed). Red admirals are one of the best examples of the natural variability in butterfly abundance; their numbers can fluctuate from one year to the next by orders of magnitude. These natural fluctuations could be behind your observation of fewer butterflies this past summer. We also had drought conditions in June and July which could have affected butterfly numbers later in the summer by drying out the host plants of the early-season caterpillars. – Dr. Naomi Cappuccino

Yes, individuals from two separate species occasionally mate and form hybrid offspring. Typically, this occurs between species that are very closely related. A good North American example is a population of swallowtail butterflies in upstate New York that appeared for the first time late in the summer in 1999. Genetic analysis has shown that these butterflies are a hybrid of the Canadian tiger swallowtail and the Eastern tiger swallowtail. Because they emerge late in the season, the new population is reproductively isolated from the parental populations which emerge early in summer. Presently, they can still mate with the parental species and produce healthy offspring in the lab. However, if the reproductive isolation persists for many years, over time the hybrid population will accumulate genetic differences from the two parental species, and possibly become a separate species. – Dr. Naomi Cappuccino

Source: Ording, G.J. et al. 2010. Allochronic isolation and incipient hybrid speciation in tiger swallowtail butterflies. Oecologia 162:523-531

Insects have many different types of ears all over their bodies. Many butterflies have ears at the bases of their front wings. We think they use them to hear bird predators. Some butterflies that fly at night use their ears to detect hunting bats. Some butterflies have ‘hearing aids’ on their wings to amplify sounds that are important to them.  – Dr. Jayne Yack

Many butterflies have ears that they probably use to detect the sounds of approaching predators, but very few butterflies actually make sounds. One good example of a sound producing butterfly is the Hamadryas butterfly, sometimes called the ‘cracker’. It has little sound producing organs on its front wings that make cracklings sounds. They make these sounds when approached by a predator, perhaps using it as a warning sound. Sometimes they also use these sound during mating interactions, in which case they would be communicating. – Dr. Jayne Yack

Additionally, caterpillars can make sounds. Check out some of the videos from Dr. Yack’s research lab here which show caterpillars making their sounds.

Many insects, including butterflies, have contact chemoreceptors on their legs. They can also taste with sensory organs on their mouth parts. Insects have sensory organs on different parts of their bodies. Some butterflies can ‘see’ with their back ends, and ‘hear’ with their wings. – Dr. Jayne Yack

Taste involves detecting chemicals upon contact or “contact chemoreception”. Butterflies do indeed have contact chemoreceptors on their feet, so yes, they “taste” plant chemicals through their feet, just as we use the receptors on our tongue to taste our food. However, a female butterfly doesn’t taste the plant leaves because she is interested in eating them herself. Her main concern is finding an appropriate plant for her offspring to feed on. She needs to detect the right combination of chemicals on a leaf to determine whether that plant is safe (not toxic) for her caterpillars before she lays an egg. – Dr. Naomi Cappuccino

Butterflies have chemoreceptors on their feet that act like human taste buds. A female butterfly will drum the leaves with her feet to release the plant juices. She is searching for the right plant chemicals and if it is a match will lay her eggs. These chemoreceptors sense dissolved sugars in fermenting fruit. A favorite snack for tropical butterflies. – Greenhouse Manager, Ed Bruggink

Yes — it’s true.  Many insects ‘taste’ with strange parts of their bodies in comparison to how people (i.e. humans) taste (and smell) things — we use our mouth and nose.  Taste (and smell) is essentially a process of detecting molecules in the environment and sending messages to the ‘brain’ for processing.  Butterflies have receptors on their feet that detect molecules in their environment — basically, detecting the molecules of/in what they are standing on.  Ditto for their antenna detecting molecules wafting along in the air (like pheromones). Is taste to a butterfly the same as taste to a human?  Well… what is perceived depends on how the butterfly interprets the messages arriving at it’s brain.  Clearly a butterfly brain is different than a human brain so it’s very unlikely that both humans and butterflies ‘perceive’ the deliciousness of an orange slice in the same way. – Dr. Jeff Dawson

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Several insect species, including bees, fruit flies and cockroaches, have been demonstrated to sleep, so it’s probably safe to assume that butterflies do, too. How do we know that insects sleep? Butterflies and other insects cannot close their eyes when they sleep, because they do not have eyelids. However, they do enter a typical “sleep posture”. For example, some native bees spend the night on a plant stem, holding on with just their mouthparts. While asleep, their eyes do not respond to moving images the way they would during the day when they are awake.

More importantly, sleep in insects is necessary to “recharge their batteries” just like it is for us. If they are deprived of sleep, they are less alert, and will sleep in late the next time they get the chance. Sleep-deprived insects have memory issues, just like students who have pulled an all-nighter cramming for an exam.

As to whether they dream, and what they dream about, we can only guess. I would like to think that butterflies dream about warm sunny days in fields full of flowers and plants to lay eggs on. I certainly hope they do not have nightmares about entomologists chasing them with a net!

Source: Helfrich-Forster, C. 2018. Sleep in insects. Annual Review of Entomology 63:69–86

Dr. Naomi Cappuccino