Blow fly

Dangerous or great?

There are about 100,000 species of fly. Of these, 1,100 are blow fly spies and about 50 of them are found in Sweden.

After a meal, with much nutrition in the body, a blow fly can fly up to about 3 km before itneeds to rest. The flight of the blow fly is erratic and unpredictable. It thus flies much furtherthan it would need to reach its target. The advantage is that it is difficult to catch forinsectivorous birds. To a certain extent, the flight mode is also due to the light fly being thrown here and there even by very weak air currents.

Appearance and characteristics

The big compound eyes of the fly consist of thousands of individual visual receptors. They provide a great depth of field and therefore do not have to accommodateto see sharply at different distances.

The visual cells of the eye are also updated very quickly, which means they can registerfaster movements than our eyes can. This makes flies difficult for us to catch. The feet of the fly have microscopic hairs with small secreting end plates. These are suckedonto the substrate with the help of van der Waals force and capillaryforce. This means that the fly can easily walk on vertical window panes and even walkupside-down in the ceiling.  Both house flies and blow flies are lairs for bacteria that cling to their wings and legs. Eachstep the fly takes leaves a small bacterial colony. Some of these bacteria can be harmful tous humans if they end up in wounds or on our food and are allowed to multiply undisturbed. Bacteria also spread from the fly's spit and faeces.However, we can take comfort in the fact that flies are an important food source for birds,lizards and amphibians.

Feeding and catching

The blow fly often eats rotten meat, rotten fruit and feces. The mouthpieces cannot bite sothe fly spits digestive fluid over the food and then sucks it in as it dissolves.

Reproduction

It lays itseggs on dead animals and faeces or in wounds on live animals. Some species lay eggs in the fur of live animals where the larvae then do great damage.