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DIPTERA.— TWO-WINGED FLIES. 



By Edmund Baynes-Reed, London, Ont. 



It has been estimated by competent authority that the insects comprise about four- 

 fifths of the whole animal kingdom ; it is therefore natural that the history of the lives 

 and habits of this large portion of animated nature should be of vast interest and import- 

 ance to mankind. 



In the recognized scientific classification of insects those possessing in the perfect 

 state only two wings are known as Diptera, from two Greek words, dis, two, and pteron, 

 wing. And we purpose in this paper to give a brief outline of the history of some of 

 the common members of this great family of Diptera — or flies, as they are more usually 

 termed. 



The same authority quoted above estimates the number of species of Diptera at 

 24,000. Prof. Packard, in his Guide to the Study of Insects, states, " There are about 

 2,500 species of North American flies described, and it is probable that the number of 

 living North American species amounts to 10,000. In Europe there are also about 10,000 

 known species belonging to about 680 genera. 



According to the distinguished Entomologist, Westwood, " The two-winged insects 

 constitute one of the most extensive orders of the Ptilota (winged insects), not only in 

 respect to numbers of distinct species, but also to the swarms of individuals of the same 

 species ; and which from their constant attendance upon man have attracted his attention 

 from the earliest ages. It is not, however, from their size that this has been the case — 

 since few species exceed an inch in length — nor is it on account of their beauty, for the 

 majority of them are of dull colours ; their forms, too, are rarely elegant, and the trans- 

 formations of many are unknown. They owe their notoriety, if we may so speak, in 

 many cases to the disgusting habits and appearances of their preparatory state — where 

 many of them revel in filth of every description — and to the annoyances caused by the reiter- 

 ated attacks of their numberless tribes in the perfect state, both directly upon ourselves, 

 and indirectly upon our living and dead property of almost every kind " 



Flies can at once be easily recognized from other insects by their having only two 

 wings ; these are transparent. Instead of the hind wings common to other insects flies 

 have two little projecting appendages, which have received the name of " halteres," or 

 " balancers." These characteristic organs may be observed in the place usually occupied 

 by the hind wings, and are kept by the insect in nearly constant vibration. There is 

 much difference of opinion among Entomologists as to the special functions or uses of these 

 balancers ; some thinking they are organs of hearing, others believing they are appendages 

 to the respiratory organs, and some being of opinion that they serve simply to regulate 

 the flight of the insect. 



Flies are suctorial insects, and, quoting again from Westwood, " their mouth is 

 formed only for imbibing fluid matter ; when, therefore, such fluid is enclosed in peculiar 

 vessels, the internal pieces of the sucker are employed as lancets to pierce the envelope, 

 and afford a passage to the fluid, which ascends by power of suction, produced by the 

 fleshy lips of the insect into the mouth." 



The head of a fly is very distinct, and is attached to the body by a very slender 

 neck ; the eyes are exceedingly large, with numerous facets ; and those of the male fly 

 in some species take up nearly the whole of the head. 



The larvae of flies are footless, fleshy grubs, of a whitish colour, and a cylindrical, 

 worm-like shape ; according to Packard, in some of the higher families they have a dis- 

 tinct head ; but in the family of Muscidce, to which the common house-fly belongs, they 

 are often headless, and are then called maggots. 



The metamorphosis, or change into the pupal state, is most complete in all the Dip- 

 tera. Like that of the Hymenoptera, the enclosure consists of a thin, transparent covering, 

 the parts being free and easily recognizable ; in many species, however, the insect under- 

 goes its change within the larval or caterpillar skin, which then becomes hardened and 

 forms a firm protecting case for the pupa. 



