AMERICAN HYMENOPTERA. 35 



what is often supposed to be the first abdominal segment. In most gen- 

 era this is split through the middle and retracted, and hence has been 

 called the basal plates. The second pair of spiracles is on these plates. 

 A pale membrane, as in Cinibex, often appears between the basal plates. 

 The pectus is the breast or under part of the thorax. The pleura or 

 side is the space between the pectus and wings. 



Abdomoi. — This is sessile, sub-cylindric ; segments distinct, with a 

 spiracle on ea<;h side of the first seven. "J'he first or basal segment is 

 attached to the extended portion of the metathorax, which resembles a 

 segment, and is often described as the first.* The ovipositor of the le- 

 niales is attached to the extremity beneath. It consists of a p;iir of com- 

 pressed saw-like plates, each of which is in two pieces, the saw and its 

 back support which is also serrate. These saws vary in shape in diflerent 

 genera, but are curved upward, serrate and ribbed on the sides. They 

 are inclosed in a pair of outer sheaths. 



Lega. — Length moderate. Trochanters 2-jointed. The ends of the 

 tibiae with two acute spines. In some genera there are one or more 

 spines on the sides of the tibia3. The four basal joints of the tarsi gene- 

 rally have a membranous appendage beneath. 



Pupa. — A soft chrysalis, when mature distinctly exhibiting eyes, an- 

 tennge, wings and legs; in some cases more or less thickened externally, 

 mostly with a parchment-like silken cocoon. Transformations in the 

 ground or on the surface, or on limbs of trees. 



Larvse. — Like caterpillars, with a horny head, and on either side 

 simple eyes; six horny pectoral, and from 12 — 16 skin-covered, ventral 

 feet. In one case in default of these last, there are two antennje-like 

 organs on the side of the final segments. (^Lydn.) 



Eggs. — Generally deposited in the leaves or ribs of plants. In some 

 few cases in slender or hollow stems. 



* Mr. Walsh (Proc. Ent. Soc, Dec, 1866,225,) has noted several of my former 

 errors of this kind. For a long time I supjiosed that there was a first segment 

 beneath these basal plates, and that the abdomen had nine segments. But if 

 one examines the larva of Cimbex, he will find but nine pair of spiracles, of 

 which in the imago the first pair appear beneath the anterior wings ; and the 

 second pair in all the lehneumonidse and other genera e.xamined, is found dis- 

 tinctly on the metathorax, back of the hinder wings, while the remaining 

 seven pair of spiracles, which in the larva, are in the seven succeeding seg- 

 ments, also follow in succession on the abdomen of the imago. 



Mr. Walsh also notes the fact that there is one more segment visible upon the 

 dorsum than ujion the venter. Burmeister states, that in the Hj-meiioptera the 

 dorsum generally has one more segment; while Shuckard says, that in all the 

 Aculeate Ilymenopiera the males have seven and the females but six segments. 

 (Burm. Man., 108.) 



