Fig. 39.—Wing of Musca domestica above, and of Stomoxys calcitrans below.
As a biting-fly and a blood-sucking fly, the habits of Stomoxys naturally differ from those of Musca domestica; but, like the latter, its distribution is almost world-wide. It is found in all temperate and tropical countries, and extends as far north as Lapland. But it is perhaps most abundant (or shall we say it has been most observed?) in temperate climates and during the summer months.
Fig. 40.—Side view of head of Stomoxys calcitrans. A, Proboscis in resting position; B, proboscis extended. (After Graham Smith.)
In any farm or country house large numbers of Stomoxys calcitrans are found in and about the cowsheds and stables, and in warm weather the same is true wherever cattle are grazing in the field. Later in the year, at the beginning of autumn, they are frequently found indoors, and in some ‘fly counts’ they have furnished quite 50 per cent. of the flies of a country house, the remaining 50 per cent. being made up of many other species and genera. When resting on a vertical surface Stomoxys generally has its head pointing upwards, whereas, as a rule, the house-fly rests upside down. The adult fly feeds upon any decaying matter; but whenever it can, it sucks the blood of vertebrates, and at times is a real nuisance to animals as well as human beings. So voracious are they that should a well-fed one be injured, the others immediately attack it and suck up every drop of blood which it had secured for its own food.
It has often been disputed whether a meal of blood is essential to the female mosquito before oviposition, but it seems perfectly clear that the female Stomoxys can produce fertilised eggs without having had a meal of blood.
Fig. 41.—Stomoxys calcitrans. Eggs. (After Newstead.)
The female lays a number of white, banana-shaped eggs a few inches below the surface of any decaying organic matter; fermenting grass from the lawn, decaying garden stuff, stable manure—each forms a favourable nidus. The eggs are laid in a heap like those of the house-fly, each heap containing from fifty to seventy. The egg is 1 mm. in length and has a grooved side, through the thicker end of which the larva escapes when the egg-shell splits.
