Green Caterpillar (Angulose Prominent?) killed by tachnid fly

2013 October 5

Sam and Rosie found this nearly 2-inch caterpillar crawling across the road at Rosie’s preschool on September 22, 2012, so they brought it home for me.

While it is mostly uniform green, the white stripes running down the sides from the head all the way down the body, with an added brown streak on the head, looks a lot like the characteristic markings of an Angulose Prominent, Peridea angulosa.

Now, I’ve misidentified caterpillars as Angulose Prominents before, so I wanted to try to be sure this time. Which would require raising it up to adulthood. But, it was not to be. See this darkened, deformed breathing spiracle? It turns out that’s a bad sign if you want to raise a caterpillar.

You see, tachnid fly larvae need to breathe, too. So they will use one of their host’s breathing spiracles as a passage to the outside so they can get some air. And the spiracle that they use ends up discolored and deformed.

And just a couple of days later, the caterpillar died while it was trying to pupae. And the tachnid fly larva came out to pupate instead.

As it turns out, the tachnid fly never came out of its pupal shell, so we’ll never know which species it was. But it was certainly a fly, their pupae are pretty distinctive.

It probably was expecting moist soil or leaf litter to pupate in, and it probably dried out and died when it ended up exposed like that. It may also have needed a cold spell to simulate the passage of a winter before it would mature and come out. This is one of the things that makes it difficult to raise a lot of insects in the temperate regions – without the stimulus of a cold winter, some of them never get the message to grow up.

One Response
  1. Anoop permalink
    November 1, 2020

    worst images

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