Saturday, April 17, 2010
March of the Chenilles 2010 Part Deux
On April 3 and 4, while the mourning cloak butterflies (Nymphalis antiopa) were eclosing, another batch of caterpillars were marching toward their destiny as pupae on the walls of my house and other suitable vertical surfaces in the neighborhood.
There were a few detours along the way. One of the caterpillars seemed taken with my coil of hose; another one travelled horizontally along the house siding for a long while casting a spiky shadow as the day grew late. Eventually, by the next day, the caterpillars were pupae hanging off the house like little fruits. There were six of them that I could find, which is more than I've seen at one time. I was thinking this is a good year for mourning cloaks.
The next morning, my daughter found a partially-pupated one laying on the brick patio between the house and the office. This particular caterpillar must have been unusually motivated to not pupate where it pooped, to have crawled all the way around the house and across the driveway and patio, passing up perfectly good vertical surfaces and in the end fail to find a place to attach before the unstoppable pupation molt occurred. It wriggled when I picked it up, an uncomfortable parody of being alive.
So I kept half an eye on the healthy pupae on the house, figuring the butterfly transformation would take over 2 weeks, as with the previous crop of pupae. On March 14, however, I noticed the pupae were gone. Well, not completely gone, anyway not all of them. A few had a couple segments left hanging as slim evidence of the apparent predation of the entire crop.
So much for the strategy of not pupating where you poop.
I suspect the predator of these mourning cloaks to be the wrens, probably Bewick's wren Thryomanes bewickii. In this terrible photo you can at least see the white stripe across the eye which is a distinguishing mark of this species. When they aren't singing from a tree top or another high place, these cute little guys are usually squirreling through the underbrush, digging in the dirt, climbing up and down branches, all in search of insects and spiders to eat. I noticed them picking adult carpet beetles off the flowers, and I attribute our lack of scale insect to the fastidious grooming these birds give my shrubs. It seems there are more of these birds than ever before, maybe a sign of a healthy bug-populated environment to support them. Anyway, it's sad to lose the mourning cloaks but I won't miss the carpet beetles.
A wren sings a beautiful complicated song from the power line overhead as mourning cloak butterflies glide past toward the melaleuca blossoms.