Friday, January 1, 2010

Gettin' their freak on!

Aside from plants, I always found moths and butterflies quite interesting, and for the past few years I've occasionally raised some native moths, as I did when I was a kid. These pics show some rather frustrated male polyphemus moths, who in their dimwitted passion didn't realize that the females they sought are inside the cage (they sense them by smell from a pheromone released by the females--and there were several in the cage) so in their desperation they were trying to impregnate each other and the towel on the top of the cage. I had hoped to attract a few males to put into the cage with the females, but never thought that so many would show up--after all I have never seen one in my area in all the years that I have lived here. The females were from stock I raised from eggs laid by females that I caught in Bluefield WV the previous summer--several species of large saturnid moths can be found there, and are fairly easy to catch by lights at night. The larvae are easily raised on Norway Maple, a dreadful invasive tree anyway, but they also will eat oak (and seem to prefer it in the wild), any other maple, and other trees as well. The cocoons can be stored over the winter in a refigerator, but should NOT be put into the freezer, since they need time to adjust to cold. I take them out in spring, usually in May, and they emerge in June. Large native moths like the polyphemus are under increasing pressure from habitat destruction and the misguided introduction of a tachnid fly, Compsilura consinnata, meant to control the gypsy moth. Unfortunately this parasitoid fly lays its eggs into caterpillars of just about any moth or butterfly species, and the maggots eat the poor thing from the inside over an extended period of time. Most parasitoid flies and wasps are much more species specific, so why this particular evil fly was introduced to this country by officials that should have known better boggles the imagination. It may be the main reason that saturnid moths and many other moths and butterflies appear to be less common than in years past, especially in the Northeast, where Compsilura is well established.
Of all the great American moths, the polyphemus moth seems to be the best at coping with human pressures. Nonetheless I hastily detatched the sleeping males from their various imaginary mates and made them fly away to hide in nearby bushes and trees, for if I left them in place they would have ended up as bird food. A few were kept and placed into the cage, where they were able to find real females to mate with the following night, so that another generation of moths could be produced. I find the caterpillars and, to a lesser extent, the cocoons make interesting props to discuss in my classes, as do the adult moths, of course. Most students haven't seen a large caterpillar or cocoon outside of a textbook, plus science curriculums sadly pay little heed to the natural history, so its nice to be able to show young folks something that is actually alive and interesting.

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