© Stuart M Bennett 2009

Calliphora vicini



Long ago, before the months were named after Roman emperors, the month we now call July was called worm month in certain parts of northern Europe. The worms concerned were blowfly larvae or maggots and it reminds us of what a problem it must have been to keep meat fit for human consumption during the summer months.
Blow flies belong to the family CALLIPHORIDAE consisting of flies of a stout nature. They have a fan of bristles close to the halteres, but with little or no post scutellum. The 4th long vein in the wing is usually bent forward near the tip. Adults soak up surface fluids with mop like mouthparts. They are most common in summer, but many species are drawn out by the sun in midwinter. Most breed in carrion and other decaying animal matter. A few of the larvae are parasites.
The blowflies most commonly seen in the house are the bluebottle, shown above, and the greenbottle.
Under normal conditions the female blowflies lay their eggs on dead animals, the smell of which can attract them from a distance of several kilometres. They also lay eggs on other decomposing matter and on faeces.

The eggs hatch in less than a day and the larvae burrow straight down into the food source. They grow very rapidly and will be full size within a about a week, and then they will normally leave the carrion. If the larvae have no opportunity to bury themselves in the ground they will crawl around until they find a suitable place in which to pupate.

Blowfly larvae found indoors may come from dead nestling birds, or from dead rats or mice. A single dead rat will provide enough food for about 4000 maggots. The creeping larvae may have an unpleasant appearance, but on the other hand they do remove the smell of a dead rat, over a period of a couple of weeks, which is much worse. The larvae will move away from the light, so they will often pupate behind panelling or under the carpet. After a further 8-10 days the pupae wriggle their way into the light and the adult flies emerge. They are immediately able to fly off, mate and start laying eggs.

Like other flies the various blowflies have been suspected of carrying diseases. They do this by picking up pathogenic micro-organisms from carrion, offal and dunghills and pass them elsewhere. Likewise there is always the chance that intestinal and other infections may be transmitted when the insect lands on foodstuffs which are not subsequently likely to be cooked or washed, and particularly if the micro-oganisms have a few days to breed on the food source. This is why there is such a strict control in supermarkets about mixing cooked and raw meats. You should also be aware of this in your fridge at home.

Also the metabolic products of such insects, i.e. faeces and vomit, themselves are very undesirable, and meat which has been tainted by them must be very carefully washed before human consumption.

Just by reading the above it is obvious that the only treatment against these sort of flies is HYGIENE...if the parrot died three days ago and you are loathe to part with it then you will get blowflies, in other words you need to find any prospective breeding site and clean it up. If you have a dead animal or bird in your chimney and you can't get to it then all you can do is to treat the room which is worst affected with a fly spray on any possible fly alighting surface, i.e. walls, lights, windows, mirrors in fact anything a fly can land on. On the whole any treatment for flies is based on treatment of the possible breeding sites.

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