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Thursday, October 20, 2011

Flesh Flies and CSI!

Since it's October I decided to focus the rest of this month's posts on Halloween inspired themes. Wracking my brains for topics, I realized something I saw last week in the basement would fit the bill nicely. Flesh flies!

Generally the Live Animal Program doesn't keep flesh flies but Shawna Joplin, Coordinator of Animal Care and Education, brought them in as a new food source for our spiders in the Spider Pavilion (open through November 6). The species we are keeping are grey flesh flies, Sarcaphaga bullata, which get shipped to us a pupa. After about a week and a half the adult flies emerge from the puparium and are ready for us to release into the pavilion.

Grey flesh fly pupae

Our adult flesh flies feeding on banana

Flesh fly emerging from its puparium

Contrary to their common name, adult flesh flies don't feed solely on flesh. In fact they just as often eat nectar and other sugary items such as rotting fruit. All flesh flies in the family Sarcophagidae are larviparous, which means they incubate eggs internally and then seemingly give birth to live young, or maggots. It is the place of "birth" that gives these flies their common namethey are deposited on any available dead flesh! In fact these flies are some of the first visitors to roadkill, discarded innards, and even murder victims. Putting these flies to work, forensic entomologists have painstakingly studied their lifecycle, so they can assist Crime Scene Investigators in determining time of death. Because they rapidly discover a body and their development times are predictable under particular environmental conditions, the time of death can be calculated by counting back the days from the life stage of the flies found living on the body.

Next time you feel like seeing these maggots in person, just do what some of our Adventures in Nature campers have doneput out a piece of store-bought liver and wait for the maggots to show up! WARNING: This is smelly, messy work! Lots of other species of flies, beetles, and other creatures are likely to show up too. Are you prepared?

Happy Early Halloween!


  1. that might be the only time i've ever seen a fly lay on its back. thanks for the great vid!

  2. No problem! I love sharing videos like this. However, I really have to thank Sam Easterson for his talent at capturing the footage.

  3. We recently found a number of pupae in an upstairs room near and on some stuffed animals. We have had a squirrel problem in the attic and we feel like the squirrels may have died in the attic attracting these flies.

    Do you think it's feasible that the squirrel died, causing a flesh fly infestation in our attic which caused pupae to fall from the attic into the room below it?

    The pupae we found were identical to these pictures and we found two dozen or so scattered around my daughter's stufed animals. Some were buried into the fur of the stuffed animals pretty deep.

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  5. What you have suggested is totally feasible! However, the pupae wouldn't have fallen from the roof above. Instead the maggots would have crawled around looking for a suitable place for pupation. In the out-of-doors maggots will often dig into soil and bury themselves, so it doesn't surprise me that they buried themselves in the fur of your daughter's toys.

    To make a positive ID on your particular flies however, we would need a sample of one of the pupa. Even if you had a picture and a measurement of length that might work too. A lot of fly pupae look very similar. Common house fly, Musca domestica, pupa look very similar! (