600 DIPTERA. 



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 per- 

 severed 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. Be- 

 sides 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 peculiarities in their forms, structure, and habits, al- 

 though 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 singu- 

 lar in its appearance and graceful in its motions than the 

 Ptychoptera clavipes of Fabricius, or club-footed Ptychoptera. 

 A new genus, called Bittacomorpha, on account of the fancied 

 resemblance of this insect to the Xeuropterous genus Bitta- 

 ciis, has lately been made for its reception, by Mr. West- 

 wood, 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. The head is small, and almost hidden 

 under the thick and hunched thorax ; the antennae are many- 

 jointed, slender, and tapering ; the hind body is long, nar- 

 row, and somewhat flattened ; the legs are very slender next 

 to the body, and increase in thickness towards the end, and 

 the first joint of the feet is swollen, oblong oval, and very 

 downy. The length of the body is about half an inch, and 

 the wings expand nearly three quarters of an inch. It 

 appears in July, and takes wing by day. As it flies slowly 



* Pages 16 and 17. 



t Philosophical Magazine, Vol. VI. p. 281. Lond. 1S35. 



