The Ecological Players in the Decompositonal Game

15 July 2007: Upper left, Phormia regina, the black blow fly; Upper right, Lucilia illustris, a green bottle fly; Lower left, Fannia canicularis, the lesser house fly; Lower right, Sarcophaga sp., a flesh fly.

OK, not much has been happening on the pig or bear carcasses. So we shall take a detailed look at some of the insects obtained during the course of this investigation.

The flies illustrated above are some of our most informative and/or interesting flies on the decomposing bear and pig. The two above represent our predominant blow flies. The green bottle fly (Lucilia illustris) is one of several species of green bottles we encounter regularly on carrion here in northeastern Ohio. It is often the first to arrive, and based on our sweeping of adult flies off the carcasses, larval collections off of the carcasses, larval collections of the wandering masses of maggots, and our rearings, we found that L. illustris was indeed the first arriver.

The black blow fly (Phormia regina) arrived and developed concurrently with L. illustris, but developed a little more slowly. Lucilia flies were only present on the carcass for a short while, followed by numerical domination by the black blow fly.

The lesser house fly (Fannia canicularis) was interesting. Not an early arriver, nor very predictable in its arrival time, it is not a precise predictor of time of death. However, the literature suggests it arrives when fecal material in the guts of the carcasses are exposed. Our observations show that this is not necessarily the only time it arrives and deposits eggs. We found that the adults lay eggs underneath the dry carcasses on the vegetation, and the larvae develop nicely on the blackened, decomposing grasses fouled by mammal decomposition. Further, we obtained eggs, larvae, and pupae of this species when we exposed raw beef.

Lastly, Sarcophaga or flesh flies are often times present in reasonable numbers on carcasses. I reared flesh flies off a dead shrew near this field site recently, and it was the only taxon present on the small carcass. We have so far recovered no individuals from any of our efforts. The lack of flesh flies is both interesting and not easily explained.

Next post, we shall provide information on more fly species taken on our pig and bear carcasses.