HYMENOPTERA 895 



suggested the common name sawflies which is applied to members of 

 this order. 



The ovipositor and its sheath consists of three pairs of appendages 

 or gonapophyses ; one pair arising from the sternum of the eighth 

 abdominal segment and two pairs from the sternum of the ninth 

 abdominal segment. The outer pair of the ninth abdominal segment 

 constitute the sheath of the ovipositor, so called because when the 

 ovipositor is not in use it is enclosed between the two members of 

 this pair of gonapophyses. The ovipositor is a double organ, con- 

 sisting of two similar blades situated side by side. Each blade con- 

 sists of two gonapophyses, an upper or posterior one, known as the 

 support or lance, and a lower or anterior one, the so-called saw or 

 lancet. The supports are the inner gonapophyses of the ninth ab- 

 dominal segment, and the saws are the gonapophyses of the eighth 



abdominal segment. 



Although each of the saws 

 is closely joined to its support 

 it can be moved backward and 

 forward along it. Figure 1132 

 represents one of the blades of 

 the ovipositor of Cimhex amer- 

 icana. 



The ovipositor of this saw- 

 fly is fitted for cutting slits in 

 Fig. I i32.-Blade of ovipositor of Cimbex ig^ves in which the eggs are de- 

 amencana; a, support; b, lancet. ^^^^^^^^ j^ ^^^^^^ members of 



this suborder that deposit their 

 eggs in the stems of plants or the trunks of trees, as the Siricidfe, the 

 ovipositor is slender and long. After a slit has been cut or a hole 

 drilled in the trunk of a tree, as the case may be, an egg is forced down 

 between the blades of the ovipositor to the nidus prepared for it. 



The larvje of the Chalastogastra are all plant-feeders. With the 

 exception of those that are leaf -miners they are caterpillar-like in form. 

 Prolegs are present in the Xyelida?, Cimbicidae, Tenthredinidae and 

 Argidce; but these are not provided with hooks as are the prolegs of 

 caterpillars. 



A striking feature of the lar\^ae of this suborder is the possession 

 of a pair of ocelli, one on each side, which in their position and in 

 their structure agree with the ocelli of adult insects, that is, they are 

 primary ocelli. This characteristic distinguishes these larvae from 

 the larvce of Lepidoptera, which have only adaptive ocelli, usually 

 several on each side (see page 136). 



A classification of the larvse of this suborder was published by 

 Yuasa ('22). 



