Can you identify an insect pupa or egg case?

Asked March 13, 2020, 6:04 PM EDT

I found about 20 small, roughly 1/2 inch long, foot-ball shaped objects on my garage floor the other day. They look like insect pupae or egg cases, not cockroach, the ends are rounded and slightly pointed, not blunt. When squeezed, as in photo, a pale greenish goo is exuded.

Polk County Oregon

1 Response

Thank you for the image. The item is a pupal case of a fly. The dent in this particular one indicates it has been injured and is unlikely to continue development.

All flies have 4 life stages: Adult; egg; larva (youngster); and pupa (a resting stage during which the youngster becomes a full-sized adult).

As an example, you can read about the life cycle of a house fly at https://study.com/academy/lesson/life-cycle-of-a-housefly-lesson-for-kids.html.

In most cases, only a highly specialized entomologist is able to determine which fly will emerge just by looking at a pupal case.

You might want to do a simple experiment to determine which fly it will be. If so, place several intact pupae in a clear container, then cover it with a porous lid, perhaps paper toweling held in place with a rubber band. Set the container somewhere you will see it daily but out of direct sunlight. Next, wait until the adult flies emerge.