One day in late July of this year, I was out on an early morning walk on the trails around Cornell’s campus. Heading down some stairs down to the Fall Creek gorge, I noticed a dead katydid on the ground and picked it up. I recognized it as a male Scudderia fasciata, the treetop bush katydid. This species lives high in conifers, and has dark striped wings to match its habitat. I usually find them either at lights or by accident, so I figured I’d keep this one as a specimen. I noticed that its head was hanging by a thread and that the entire head and thorax seemed to be empty. In stark contrast to this, the katydid’s abdomen was brown and bulging. Perhaps it was rotting? As I peered at it closer, a scene straight out of the movie Alien – four huge wriggling fly maggots burst forth from the katydid’s carcass! I am not one to be creeped out by insects, but this was such a shock that I dropped the whole mess! This was an especially creepy scene given that katydids are some of my favorite insects. After a moment I realized that this was a golden opportunity to see what fly species would be parasitizing bush katydids in upstate New York. I gathered up the fly larvae and dead katydid and placed them in a container with some soil.
In a few hours, the maggots had dug into the soil and pupated. I had no idea how long they would remain there, but less than two weeks later I looked at the container and four small flies were flitting around. They were sarcophagids, a group known as “flesh flies” that are known for feeding on dead bodies but which also contains species that parasitize other invertebrates. They are quite difficult to identify from photos alone, but I kept the specimens and hopefully I will be able to pin an ID on them some day.