Vole sharing

One of our cats left this vole carcass on our patio. When I went out to hang the washing I noticed that a wasp had landed on it, and was trying to bite off the nose, which is the most exposed and tender part. Picnickers will know that adult wasps are attracted to and feed on sweet things, but the grubs are carnivorous. The adults bring them prey which is mainly other insects, but may also include carrion, which is sliced up using their sharp mandibles. The prey is chewed up into a paste by the workers and queen and fed to the grubs. As many of these prey items are regarded as "pests" by gardeners, it is clear that the wasp should be regarded as the gardener's friend rather than feared. In return for the protein the grubs exude a sweet secretion in their saliva which is lapped up by the adult wasps.

Once the wasp had removed part of the nose, it was joined by first one, then several green-bottle flies. The females lay a mass of eggs in a wound, a carcass or corpse, or in necrotic or decaying tissue. The eggs hatch out in about 9 hours in warm moist weather, but may take as long as three days in cooler weather. The larva feeds on dead or necrotic tissue for 3 to 10 days, depending on temperature and the quality of the food. During this period the larva passes through 3 larval instars. The green-bottle is an important species to forensic entomologists. Like most Calliphorids, the insect has been heavily studied and its life cycle and habits are well documented. Accordingly the stage of the insect's development on a corpse is used to calculate a minimum post mortem interval, so that it can be used to aid in determining the time of death of the victim. The presence or absence of green-bottle larvae can show a lot about the conditions of the corpse. If the insects seem to be on the path of their normal development, it is likely that the corpse has been undisturbed. If however, the insect shows signs of a disturbed life cycle, or is absent from a decaying body, this suggests post-mortem tampering with the body. Because it's one of the first insects to colonize a corpse, it is preferred to many other species in determining an approximate time of colonization. Developmental progress is determined with relative accuracy by measuring the length and weight of larval life cycles. CSI on the patio!