#tachinids

[ljsbugblog]

Unknown Bristle fly (family Tachninidae).

[pterouras]

Been a while since I’ve made a long educational post so…

Many times I’ve collected caterpillars from the wild to rear, which last year most prominently included the spicebush swallowtail (Papilio troilus), my bugsona inspiration. Usually these larvae fare just as well as purchased ones, but the wild is a harsh place and sometimes when you think you have something going, you see a hole chewed out in your caterpillar’s chrysalis…

This is an ichneumon wasp, one of many insects that parasitize bug larvae. There are many different types of these creatures, but this particular one is known as Trogus pennator, and its genus is unique for preying exclusively on swallowtail butterflies. These wasps are very picky and this species only parasitizes a few species of butterfly; including the unfortunate victim I took home.

It was initially disppointing to see this wasp emerge from the chrysalis instead of the butterfly I was expecting. Even though I offered plenty of protection indoors this wasp had killed my butterfly anyway. Despite that, I decided to safely release the wasp outside, allowing it to continue on in its life cycle.

Why is that?

The way these wasps parasitize their victims ensure the caterpillars have been doomed from the start; there wasn’t anything I could really do about it. In the end, these wasps are just as much animals as the caterpillars I was rearing. While brutal and unsightly in its habits, this wasp is just another creature fighting for survival and to carry on its bloodline. It was unfortunate that I had lost a caterpillar, yes. Losing them can really hurt, I know this feeling firsthand. But the wasp that killed it had just as much a right to live too. This was only its way of life, and so I let it go with no harm done.

However there’s another important reason for this release I feel I should mention; all parasitoid insects play a very important role in the ecosystem. Caterpillars can very much be pests too; cutworms are a notable example that are quite common around here, but there are many problematic species that can decimate plants if left unchecked. This is where parasite insects come in; they are extremely effective natural pest control that ensure a caterpillar will not make it to its adult form, while producing more spawn that will also help control pests.

These many insects are necessary to prevent grubs and larvae from doing too much damage. Even Trogus play their part as well. Swallowtail caterpillars have many extremely effective adaptations and defense that allows them to evade predation from traditional caterpillar predators such as birds. Without proper predation from other animals even these butterflies may become too overbearing on their environment; it’s insects like Trogus that are specifically adapted to prey on swallowtails that keep them in check and allow both bugs to maintain a healthy ecosystem prescence.

This isn’t the only time I’ve dealt with parasitism. Another spicebush swallowtail I took in fell victim to what I believe are tachinid flies, though I don’t have any photos so I can’t make identifications. It’s not fun to experience, but it remains important in the end!

It might be unfortunate to see a parasite insect emerge from your caterpillar in rearing, especially if your larva is non-problematic like many saturniid moths. And truth be told, it’s probably a miserable experience for the caterpillars themselves. However, don’t blame the wasp or flies! They’re just doing their part in maintaining a balanced ecosystem, and they deserve just as much respect. So do let them live and allow them to carry on their work! The kindness will be appreciated by the bugs and environment around you.

[maggotsandcream]

[image description: that meme where one guy stops another guy from approaching a woman where the guy being stopped is labelled "me wanting to make a WBIT? post about Tachinid flies" and the guy doing the stopping labelled "the astounding diversity and lack of common names in the family Tachinidae" end description]

What Bug Is This? may never have a tachinid post because it would require so many photographs to get the right idea of what they’re like because they’re chubby, dark and fuzzy except for the ones who are thin, colorful, and shiny, you know? There are a few species with common names, but I really wish there were more. Plus, the genus that folks text me photos of most often doesn’t actually have a common name and I would want to start there.