Cutworm parasite
I’m doing a short write up of this fly just to get you thinking a bit. It was observed April 29, 2024 on San Juan Island, WA. While identification to Genus/Species may not be possible until I can actually catch a specimen to be keyed out, it is Family Tachinidae and Tribe Goniini. Hoping to come back with at least a Genus update at some point.
What I want to SHARE is the life history of this tribe of flies. The Goniini flies are parasites of various Lepidoptera, mostly Noctuids, Arctiids, and Lymantriids. Translating this for you a bit, it would be cutworms (if you’re a gardener) , tiger moths, and tussock moths.
How does this play out?
The female Goniini fly lays a “black microtype,” usually ovate and flattened egg, varying in size from very small to medium, on foliage utilized by the feeding host caterpillar. The caterpillar (usually Noctuids) munch the foliage, ingesting the fly egg. The caterpillar will continue feeding and then wander off to complete its life cycle as a pupa. At some point after ingestion by the caterpillar, the fly egg hatches and the fly larva develops inside the body of the pupating moth that is inside its chrysalis.
A myriad of ecological relationships exist in nature that are often unobserved. Many remain undescribed or unknown. Sometimes, they are disrupted by humans who intervene out of ignorance. If you’re one of those folks who squish what you believe are cutworm pupae in your garden bed, you might be smooshing the pest predator developing inside.
References
- No Author. 2024. Tachinidae. Spencer Entomological Collection. Beaty Biodiversity Museum. https://www.zoology.ubc.ca/entomology/main/Diptera/Tachinidae/
- Wood, D. M. 2013. Manual of Nearctic Diptera. Tachinidae Resources. https://www.uoguelph.ca/nadsfly/Tach/Nearctic/Manual/Manualhome.html
- Cole. Frank, R. 1969. The Flies of Western North America. University of California Press. Berkeley, CA.