Friday, July 27, 2012

On the Wing

The Children's Garden is the place to be if you want to view one of nature's prettiest insects: tiger swallowtail butterflies. They love the Joe-pye weed.  I found some fun facts about this insect on the Encyclopedia of Life website.

The female swallowtails are dimorphic, meaning they can be different colors.  Some females look almost exactly like the males, with the same tiger striping but a little more blue on their wings.  Other females are completely black, and might be mistaken for being black swallowtails. Both colorings are beneficial in some way.  The tiger striping distracts predators, and the black version imitates the poisonous blue swallowtail.  In the pictures below, the top one is male and the subsequent photos are the normal and black forms of the female.  The black version was a lot more difficult to sneak up on for some reason.

These butterflies seem fairly common, which is not surprising if you know something about host plants.  Many people think the way to attract butterflies to your yard is to plant things like Joe-pye weed or butterfly bush or some sort of flowering plant that butterflies are known to visit.  This will work, but to sustain a butterfly population, the "host plants", or the plants that the females will lay their eggs on, need to also be present.  The tiger swallowtail is so common because the larvae are able to feed on various woody plants, so the disappearance of one host plant is not such a big problem for them.  Females lay eggs on a variety of poplars, birch, cherry, ash, apple, maple, willow, magnolia, and tulip tree, among others.

Fun fact: the first three instars (or stages) of the caterpillar look like bird droppings.  This is quite effective in protecting it from birds.  I'm guessing that doesn't look to appetizing.  There is a cool picture of that if you look around on the Encylopedia of Life website.  

I also caught a glimpse of a monarch while I was chasing the swallowtails around. These butterflies do not have a wide range of host plants.  The host plant for monarch is milkweed.  The adults feed on the nectar of many different flowers but will only breed where milkweed plants are found.  The host plant provides the monarch with its best defense.  Milkweed contains compounds that are toxic to many vertebrate herbivores. The larvae ingest these toxins, and then these compounds become present throughout their bodies including wings and exoskeletons so both larvae and adult are toxic to many predators.  I could go on for pages about monarch migration, but the work week is coming to a close and so is this post. 

Come visit Welkinweir!

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