518 HYMENOPTERA. 



coming to their growth, and passing through all their trans- 

 formations, -within six or seven weeks from their first ap- 

 pearance. 



The names of above sixty native species of saw-flies may 

 be found in my " Catalogue of the Insects of Massachu- 

 setts." Some of these are very interesting in their appear- 

 ance and habits in the caterpillar state. In what follows, 

 an account will be given of one of the largest species, and 

 of some smaller kinds, that have been found very injurious 

 to cultivated plants. 



Our largest saw-fly belongs to the genus Oimbex (Plate 

 VIII. Fig. 12, Oimbex Laportei). Tins name was origi- 

 nally given by the Greeks to certain insects resembling 

 bees and wasps, but not producing honey. It therefore 

 applies very well to some kinds of saw-flies, such as the 

 female of this species, which, at first sight, might be mis- 

 taken for a hornet. Her head and thorax are shining 

 black. Her hind body is oval, and of a steel-blue or deep 

 violet color, with three or four oval yellowish spots on each 

 side. Her antennae are buff-colored, except at the base, 

 where they are dusky; they are short, and end with an 

 egg-shaped knob. Her wings are smoky brown, and semi- 

 transparent. Her legs are blue-black, and her feet pale 

 yellow. The length of her body varies from three quar- 

 ters to seven eighths of an inch, and her wings expand an 

 inch and three quarters or more. In the manuscript lec- 

 tures of the late Professor Peck, she is called Oimbex Ulmi, 

 because she inhabits the elm. The male is the Oimbex 

 Americana of Dr. Leach, and differs so much from the 

 female, that it might be taken for a different species. His 

 body is longer and narrower than that of the female, and 

 wants the white spots on the sides ; and there is a trans- 

 verse, oval hole, filled with a whitish film, behind the tho- 

 rax, which is hardly perceptible in the other sex. His 

 hind legs are very thick; the shins are bowed, and hairy 

 within; and the first joint of his feet ends with a stout 



