SAW-FLIES. PARASITIC WASPS. 



The XIPHYDRIID/E are moderate-sized creatures with 

 quite a long neck; the ovipositor is cylindrical; the last 

 dorsal plate of the abdomen (see Siricidas) does not end in a 

 triangular or lance-shaped process. 



The SIRICID/E are the Horn-tails. The last dorsal 

 plate of the abdomen ends in a triangular or lance-shaped 

 process. These insects are wood-borers and sometimes 

 emerge in our houses from fire-wood or even furniture. 



The adult Pigeon Tremex is well repre- 

 Tremex 



columba sented in Plate LXXXVII. It is also 



called Horn-tail. The cylindrical larva, 

 with three pairs of legs near its head and a "horn" near 

 the other end, bores in the trunks of diseased maple, elm, 

 and other trees. It pupates in the larval burrow after 

 making a cocoon of silk and chips. On emerging, the 

 adult leaves a hole about the diameter of a lead pencil. 



ICHNEUMONOIDEA 



This is one of the most important groups of insects, from 

 an economic standpoint, but the classification of its species 

 is no task for any but the specialist. Many millions of 

 these ichneumon "was^s" are working every year, with 

 the assistance of other parasitic insects, in keeping down 

 insect pests and insects which might be pests. To be 

 sure, others, as "secondary parasites," prey upon the foes 

 of our foes, and it is one of the problems of professional 

 economic entomologists to know one from the other; 

 but in this group so much depends on the general looks of a 

 species, its "habitus," that experience and named collec- 

 tions are necessary to easy identification. 



The easiest family to recognize, in a general way, is the 

 EVANIID/E; the abdomen appears to be joined to the top, 

 instead of to the end, of the thorax. Evania urbana and 

 appendigaster (Plate LXXXVIII) have blunt abdomens 

 and breed in the eggs of cockroaches. 



Plate XXXVIII shows the cocoons of one of the 

 BRACONID^E on a Sphingid caterpillar. The larvae live 



411 



