356 MOTIONS OF INSECTS. 



The bodies of these are light, their wings narrow, and 

 their legs long, and they have no winglets. Next are 

 those whose bodies, though slender, are more weighty — 

 the Asilidcc, Conopsiddc, &c. ; these have larger wings, 

 shorter legs, and very minute and sometimes even obso- 

 lete winglets. Lastly come the flies, the Muscidce, &c., 

 and their affinities, whose bodies being short, thick, and 

 often very heavy, are furnished not only with proportion- 

 ate wings and shorter legs, but also with conspicuous 

 winglets. From these comparative differences and dis- 

 tinctions, we may conjecture in the first place — since the 

 lightest bodies are furnished with the longest legs, and 

 the heaviest with the shortest — that the legs act as 

 poisers and rudders, that keep them steady while they 

 fly, and assist them in directing their course » ; and in the 

 next — since the winglets are largest in the heaviest bodies, 

 and altogether wanting in the lightest — that one of their 

 principal uses is to assist the wings when the insect is 

 flying. 



The flight of the Tipularian genera is very various. 

 Sometimes, as I have observed, they fly up and down 

 with a zigzag course; at others in vertical curves of small 

 diameter, like some birds ; at others, again, in horizontal 

 curves : — all these lines they describe with a kind of 

 skipping motion. Sometimes they would seem to flit in 

 every possible way — upwards, downwards, athwart, ob- 

 liquely, and sometimes almost in circles. The common 

 gnat {Cultw pipicns) seems to sail along also in various 

 directions. The motion of its wings, if it does not fly 



' To those tliat frequent meadows and pastures [Tipula olcracea, 

 L. &c.) they are also useful as I have before observed, as stilts, to 

 enable them to walk over the grass. Reaum. v. Pref.'i. t. m.f. 10. 



