OLPTERA. 217 



OEDER DIPTERA. 



WfNGS two, with few veins, not clothed with scales or hair; 

 hind wings replaced by rudimentary battledore-shaped organs, 

 called halteres, or poisers ; mouth furnished with a proboscis ; 

 female stingless, rarely provided with a conspicuous ovipositor ; 

 metamorphoses complete ; larvaj most frequently worm-like mag- 

 gots, without feet ; pupa3 inactive. 



Few Orders of insects have been less studied than the Diptera, and 

 consequently our knowledge of them is very imperfect, especially 

 as regards foreign species. The number of recorded British species, 

 is not much inferior to that of the Colcoptera and Hymeno'pLera ; 

 and although a much smaller total number of species is at present 

 known from all parts of the world, and although experienced 

 entomological travellers assert that DvjMra, in some tropical coun- 

 tries at least, are far less abundant in comparison than in England, 

 yet we may fairly assume that, when all the Orders of insects have 

 been equally well worked out, the Coleoj^tera, Hipncnoptera, and 

 Diptera will stand on a nearly equal footing as the three largest 

 of all. Baron Osten-Sacken has expressed an opinion that the 

 real number of Diptera existing in North America will vdtimately 

 prove to fully equal if not to exceed that of the Coleoptera. 



The food, habits, and structure of the Diptera vary so much 

 that it is better not to allude to them in these introductory re- 

 marks. The Order has been divided into a great number of 

 families, many of which will fall into the typical family Muscidce, 

 though this is subdivided into two large sections, and these again 

 into numerous sub-families. 



Although the Diptera are commonly spoken of as having only 

 two wings, the hind wings are always represented by two small 

 organs, called Jialteres, or poisers, which somewhat resemble a battle- 

 dore in shape. If these are removed, or seriously injured, the in- 

 sect becomes quite incapable of directing its flight. In addition to 

 these, some species are provided with two more or less conspicuous 

 lobes at the base of the wings, called ahdce or winglets. 



