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.