Grey Fleshfly Sarcophaga sp
And here we go again. On the internet usually the Grey Fleshfly is called Sarcophaga carnaria. Very often people are dead wrong. In Western European countries the number of species in the genus Sarcophaga varies from 20 to well over 50! All are extremely similar: grey and with chess board markings on the body. To tell all those species apart, it is essential to study the genitals under a microscope. In insect guides and field guides often Sarcophaga carnaria is shown as the ultimate example of a Grey Fleshfly. Thus many people think that is the animal they have seen. Alas, with at least 20 species around, chances are it is a different species all together.
Despite the name Fleshfly, the larvae of most species do not eat decaying meat. Most species deposit their eggs on a carcass. The larvae go inside to hunt for other insectlarvae. And the larvae of some species even are parasites. The larvae of the true Sarcophaga carnaria for instance are parasites to Earth Worms. These are eaten from within in a matter of days. Grey Fleshflies do everything in a hurry. The females of some species do not even lay eggs. The eggs hatch inside the mother fly. So she gives birth to active larvae. When conditions are good the larvae may pupate only some 4 to 5 days after their birth. And pupation takes only some 5 days. So in less than two weeks there may be a new generation of Grey Fleshflies.
The animals in the pictures all are Grey Fleshflies. But we have no single clue about the exact species. They even could all be the same species, or all be separate species.