Archive for October, 2010

California Oak Moths

Monday, October 4th, 2010

Late one afternoon at the Bluffs last week I noticed a large number of California oak moths (Phryganidia californica) fluttering around a small coast live oak (Quercus agrifolia). The tree is right by the Lois Sidenberg Overlook sign, across from the bathrooms at the south end of the Viola Field parking. I wondered what the moths were doing, until some fluttering on a branch called my attention to these three moths:

That’s a female moth on the top, a male moth (identifiable by his feathery antennae) mating with her below, and a second male fluttering off to the side. That second male presumably was attracted by the female’s pheromones, but was too late on the scene to mate with her.

When I looked closer, I realized that the tree was full of oak moth caterpillars. Here’s a shot I took of one of those:

The California oak moth population rises and falls on a 6-8 year cycle. At population peak, stands of oaks can be completely defoliated. Interestingly, healthy oaks appear not to be harmed by these outbreaks. According to a 1986 postdoctoral study by David Hollinger of Stanford, nitrogen cycling is accelerated during the outbreaks, such that the moths actually help fertilize the soil, improving the oaks’ longterm health. See Herbivory and the cycling of nitrogen and phosphorus in isolated California oak trees.

Here’s a short video I took:

At the time I shot that video, I was transfixed by the beauty of the moths’ mating flight. In my memory, the scene is as quiet as a cathedral. After a few minutes I noticed another sound: the gentle, rain-like patter of caterpillar frass falling onto the leaves beneath the tree.

Watching the video after I downloaded it from my camera, the dominant sound is the traffic on the 101 freeway. I guess my brain filtered that out. Good job, brain.

Update: I went back later and noticed a bunch of pupae in an oak on the edge of the Viola Field parking. Here’s my favorite of the shots I got of those:

I also found this: the exuvia left behind after an adult moth emerged:

Invertebrate Tracks in the Coastal Dune Habitat

Sunday, October 3rd, 2010

I like being a volunteer docent at the Carpinteria Salt Marsh Nature Park, but it’s also pretty fun when no one shows up and I get to give myself a tour. That’s what happened yesterday.

I noticed some interesting tracks by the boardwalk in the coastal dune habitat. I suspect this collapsed tunnel is from a globose dune beetle (Coelus globosus):

I’m curious what made this trail winding its way down (or up?) this slope:

It reminds me a little of a millipede trail, like this (much larger) trail from 300 million years ago, or this video of a modern millipede leaving its tracks in the sand.

I don’t have any particularly good idea what made this trail. I think I might be seeing a double line, possibly with three sets of footprints outside them:

I previously corresponded with Charley Eiseman (co-author of Tracks & Signs of Insects and Other Invertebrates) about how neat it would be if there was a site like, but focused on tracks and signs. I’m thinking of taking that on; it sounds like it would not be too difficult to set up such a site using Drupal, which I gather is the tool they used to create I’m not sure I want to take on another project, but it would be awfully neat to have access to a site like that.