Friday, April 03, 2009
Recently, at the Public Library
I was walking by the Tustin Public Library recently when I happened to notice some butterfly pupae hanging within the vine that clambors over the chain link fence there between the old decrepit library and the new one that is under construction. OK, in reality I was purposefully looking for signs of gulf fritillaries since the vine is passion vine and that is the exclusive larval food for agraulis vanillae. The chrysalises closely resemble dead leaves among the foliage, I suppose as camoflage protection from predators. On close inspection, though, you can see small round holes in the outer shell, evidence of apparent parasitization of the developing butterfly inside. This chysalis had two holes, maybe exit holes of the developed adult parasite or entrance holes for the larval parasite or the egg-laying female.
At the time the parasitized chrysalises were found, some well developed caterpillars were also on the vine doing their worst. When I returned a couple of weeks later I found these larvae had pupated, as there were some new chysalises hanging among the passion vine tendrils. This one had a suspiciously tenacious fly or wasp on it which clung to the chrysalis even when I disturbed the nearby foliage for a clearer view, apparently unwilling to give up its prey? host? or just a convenient resting place? The thing resembles a milichiid fly, which are famous for glomming onto prey captured by other predators, usually spiders. Guilty as charged, just a simple thief, or an innocent caught in the wrong place at the wrong time?
The gulf fritillary has become common around here ever since gardeners started growing passion vine, enabling the species to breed. I see them flying most of the year; they nectar frequently at pentas, basil, and lantana in my garden. Someone said about 1 in 600 butterfly eggs make it to a successful breeding adult. With those odds I like to appreciate most every one I see.
The chain link fence where the passion vine grows that nurtures this butterfly population may be torn down soon, when the new library is completed. I'm thinking the passion vine will go, too, to be replaced by agapanthas, daylilies, privet hedges, etc. So any agraulis vanillae which arise from this vine shortly before its demise will need to seek out a new passiflora on which to lay eggs. Maybe I'll plant one; it's not like the gulf fritillary is endangered, but on the other hand neither is empty space along my property line.
4/27 Update: So I was walking by the library today. The sign is up on the front of the building. Yep, those are flowering pear trees lining the walk to the front doors. Oh and there will also be bird of paradise planted someday soon, so we can add one more the plant diversity here. The fence and the passion vine had been removed. A gulf fritillary approached from the north, glided over the roof of the old library, and couldn't help but notice that her breeding ground was gone. She flew off.
Also, I have noticed many of these butterflies flying in my yard the past couple days. Several of them popped out from the ligustrum japonicum texanum hedge along the driveway . . . a bit of a mystery as 1) the privet is not in bloom and therefore not available as a nectar source, and 2) privet is not remotely related to passionvine and couldn't be used as (or even mistaken for?) a larval food plant.