DIPTERA. 481 



and by the latter, the plants will not come into blossom until 

 the flics have disappeared. In those parts of New England 

 where these insects have done the greatest injury, the cultiva- 

 tion of fall-sown or winter grain has been given up ; and this, 

 for some years to come, will be found the safest course. The 

 proper time for sowing in the spring will vary with the latitude 

 and elevation of the place, and the forwardness of the season. 

 From numerous observations, made in this part of the coun- 

 try, it appears that grain sown after the fifteenth or twentieth 

 of May generally escapes the ravages of these destructive 

 insects. Late sowing has almost entirely banished the wheat- 

 flies from those parts of Vermont where they first appeared ; 

 and there is good reason to expect that these depredators will 

 be completely starved out and exterminated, when the means 

 above recommended have been generally adopted and perse- 

 vered in, for several years in succession. 



In the introductory chapter* a short account has already 

 been given of the habits of the various kinds of gnats and 

 flies, belonging to the principal families of this order. Besides 

 the species that are injurious to vegetation, which have been 

 now described, there still remain some of our native flies, that 

 deserve a passing notice, on account of their size, or of pecu- 

 liarities in their forms, structure, and habits, although few of . 

 them are to be included among the insects which are hurtful 

 to plants. 



Among our long-legged gnats there is no one more singular 

 in its appearance and graceful in its motions than the Ptycho- 

 ptera clavipes, of Fabricius, or club-footed Ptychoptera. A 

 new genus, called BiUacomorpha, on account of th^ fancied 

 resemblance of this insect to the Neuropterous genus Bittacus, 

 has lately been made for its reception, by Mr. Westwood.f 

 This pretty gnat is of a black color, with a broad, white stripe 

 on the face, a short, white line on the fore part of the thorax, 

 and three broad, white rings on the legs. The sides of the 

 thorax are silvery white, and the hind body is dusky brown, 

 with a narrow white line on the edges of each of the rings. 



* Page 13. t " Philosophical Magazine," Vol. VI., p. 281. Lond. 1835. 



61 



