Tuesday, November 27, 2012

Discovery Corps Wants to Know – Part 2

Last week’s questions from Discovery Corps youth specifically pertained to our Tropical Butterfly House. This week, Life Sciences Manager Sarah Moore answers their more difficult questions regarding the unique lives of butterflies.

What are butterflies’ skeletal/support structures like?

Like all insects, butterflies’ bodies are protected by an exoskeleton; an exterior covering that serves the functions of skin in protecting them from the environment, and as rigid support structure. Their muscles attach to this outer covering. Insects exoskeletons are made of a hard substance called chitin.

In the case of winged insects, the wings are kept rigid with veins, which are used for structure as well as to transport fluids and oxygen.

What are butterflies’ main predators?

The list is long. Primates, snakes, toads, birds, lizards, spiders, ants, dragonflies, and wasps are known to eat butterflies. They are also eaten by parasitoids – a special kind of predator that lives inside the host’s body and eats it gradually. These are usually wasps and flies.

A few human cultures eat butterfly pupae.

How do butterfly bodies’ work; i.e. how do butterflies communicate with each other?

I am not 100% sure what this question means, but I’m going to talk about how they communicate because I think it’s cool. A lot of butterfly communication is about mating and territory.

Butterflies have great color vision, but they don’t see detail well from a distance. When a male butterfly sees a shape bobbing up and down in air, he will fly over to investigate. When he gets nearer, he starts to refine his first response.

If he finds another male, or a butterfly of a different species, he will try to chase it away. Usually when you see spiraling butterflies flying around each other, that’s what’s going on. It’s very pretty, but they are enemies!

If it appears to be a female of his own species, he will start to court her. He flies over her and lets her see his wing colors and in some cases, produces pheromones that give her additional information about his species.

If the female is interested, she will stay where she is, take a receptive posture and the butterflies will mate.

She may not be interested. They could be different species, or she could have already found a mate, or she might just not be impressed. In these cases the female will either fly away or will close her wings and take a rejection posture. The male will often keep trying to court a female who has rejected him. If you see a butterfly perched on a plant, with another similar colored butterfly hovering back and forth around it, that’s probably a male trying to entice a female.

But there are more subtle interactions between butterflies as well. Heliconius butterflies (the Longwings) roost and fly as same-species groups because the older individuals have found good nectar sources and safe sleeping places. And migratory butterfly species form groups at certain times of year to pool their resources during long flights.

Discovery Corps is Pacific Science Center’s youth development program for high school students. For more information contact discovery.corps@pacsci.org or call (206) 443-2884.

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