476 SYNOPTIC COLLECTION. 



legs. The cocoon (fig. 2) is spun by the larva for the 

 protection of the pupa (fig. 3). In these ways the gener- 

 alized Hymenoptera prove their kinship with the Lepi- 

 doptera. 



The adult Emphytus (fig. 4) has a robust body and 

 the junction of the thorax and abdomen is broad, as in 

 the generalized Lepidoptera. The mouth parts are spe- 

 cialized by addition, being adapted for biting and sucking. 

 The two pairs of wings are membranous with few veins, 

 and the posterior pair is much smaller than the forward 

 pair. The ovipositor has become modified into a pair of 

 saws by means of which the insect makes holes in leaves 

 wherein its eggs are deposited. 



Many of these characters are more plainly seen in one 

 of our largest sawflies, Cimbex americaria Leach (No. 

 1214), and the saws of Cimbex sylvarum are figured in 

 PI. 1215. Here they are spread out horizontally and the 

 toothed edges of the saws are seen on the outer side. 



Another generalized family of the Hymenoptera is the 

 Siricidae or horntails. The larvae of these insects, how- 

 ever, show marked adaptation of structure to habit. For 

 instance, the larva of Tremex columba Linn, lives in wood 

 and this habitat has brought about a reduction in the size 

 of the legs and a loss of the prop-legs, causing the insect 

 to resemble the wood-inhabiting larvae of the Coleoptera. 

 The pupa is protected by a cocoon of silk and wood 

 chips. 



The adult (No. 1216) has a sessile abdomen like the 

 sawflies. The ovipositor, in this case, is a boring imple- 

 ment instead of a saw, and it is used for boring holes in 

 trees in each of which an egg is deposited. 



Cynipidae. It has been pointed out by Dr. Adler 1 that 

 the galls of Cynipidae may be arranged in groups of con- 

 stantly increasing complexity, beginning with those like 



'Oak Galls and Gall Flies, 1894; English transl. by Straton, p. 

 xxxiii. 



