The Monarch Monitoring Project is a long-term study on monarch migration through Cape May, NJ. It is a part of the New Jersey Audubon Research Department, and closely affiliated with the Cape May Bird Observatory.

Sunday, October 12, 2014

Winding down

North-northeast winds for most of the day, full sun, and cool temperatures left today open to possible migrants. As it turned out, activity was low and the usual booming butterfly bushes on Cape May Point were only weakly scattered with Monarchs. Today we had our last demo and so things are seeming to slow down, both with visitors and Monarch migration.

Now for a little lesson!

Today I found a chrysalis in the tank at the CMBO that had been parasitized by a Tachinid fly. This is what it looks like. (The puparium is not visible, it had already emerged when I found this.)

The female Tachinid fly will lay its eggs inside of the living Monarch caterpillar. The caterpillar survives this process, and goes on throughout its regular life stages. That is, until it metamorphoses into a chrysalis. Brown blotches start to form on the chrysalis. A hole opens up, and a fly puparium emerges. It dangles down from a thin white string, landing on the ground beneath. Tachinid flies are not the only parasitoid of Monarchs, but it is probably the most common one locally.

A Tachinid fly

It's an unfortunate but interesting process, one of the many ways that insect lives are intertwined and interdependent.

1 comment:

  1. Yes, insect lives are intertwined. It is good to remember that Lespesia archippivora, the tachinid that parasitizes monarch caterpillars, also feeds on a number of other insects, including some serious pests. In fact, it is used as a biological control of armyworms. So, in an almost paradoxical way, it may be helping monarchs by allowing us to reduce pesticides.