FLIES. 607 



are unjointed, and the abdomen has from four to seven joints, and is generally 

 soft. The larvae are footless maggots, and are either parasitic, or live on 

 decaying animal and vegetable substances. The MuscidcK are divided into 

 two main sections : the Muscidce Calypterce, in which the appendages called 

 alulae, or winglets, are present ; and the Muscidce Acalypterce, in which they 

 are absent or rudimentary. (The alulae must not be confounded with the 

 halteres, or poisers, which are drumstick or battledore-shaped organs, which 

 are considered to correspond to the hind pair of wings in four- winged insects.) 

 Each of these two sections is divided into several large sub-families, the 

 more interesting of which we will now proceed to consider. 



The Tachinince, are a sub-family remarkable for the very bristly 

 abdomen of most of the species. The larvae are parasitic on various species 

 of Lepidoptera, and the flies, which are rather numer- 

 ous in genera and species, are frequently found on 

 the flowers of wild carrot, and other Umbelliferce. A 

 species of this sub-family has been reared from a nest 

 of the gregarious larvae of a West African moth of 

 the genus Anaphe, and is here figured. 



The typical sub-family of the Muscince includes a 



. large number of our most familiar flies ; and among 



Twic7na a t s\ze.' ** them ^he true house-fly, Musca domestica (Linn.), 

 which is blackish, more or less varied with grey, and 

 with the base of the abdomen reddish ; it is about one-third 

 of an inch long. The various organs of this insect : the House-Flies, 

 compound facetted eyes, the proboscis, and the peculiarly 

 complicated foot, all form interesting microscopic objects, and have often 

 been described and figured in books on natural history. It is now believed 

 fhat the pads of the foot do not support the insects when walking on a ceiling 

 or window-pane by performing the office of suckers, but that they exude a 

 viscid fluid which enables the insects to adhere to a smooth surface. The 

 larvae of Musca domestica live in dung, or in any sort of animal or vegetable 

 refuse ; and owing to the much greater cleanliness of our houses and en- 

 closures, to what was the case formerly, flies are not nearly so numerous and 

 troublesome as was the case even thirty or forty years ago. They do not 

 bite or sting, but there is a greyer fly, Stomoxys calcitrans (Linn.), which comes 

 into houses in wet weather, and bites sharply. Its pupae have been found in 

 horse-dung, in which the larva very probably feeds. But any flies can convey 

 the infection of diseases which can be communicated in this manner, even 

 those which do not bite ; and ophthalmia is frequently thus communi- 

 cated in Egypt ; and the bite of flies that have been feeding on putrid 

 substances is still more dangerous. The mosquitoes in the East Indies are 

 even said to convey the germs of a small blood-parasite from one person to 

 another in this manner. At the best, therefore, flies are undesirable visitors 

 in our houses ; but they are not allowed to increase indefinitely, but are liable 

 to various natural checks. They are frequently seen in autumn plastered to 

 the windows by a white fungus, which has spread over and round them till 

 it has killed them. They are also frequently seen with the curious little 

 creatures called false scorpions (belonging to the Arachnide family Cheliferidce) 

 clinging to their legs. These resemble microscopic scorpions without the 

 tail, but it is doubtful if they are really injurious to the flies, which, it has 

 been suggested, they may use as winged steeds to carry them to fresh fields 

 and pastures new. 



