HYMENOPTERA 



897 



The Siricidae is a small family ; only about fifty species represent- 

 ing five genera are known. The North American species, of which 

 there are twenty, have been monographed by Bradley ('13). 



The larvffi bore in the trunks of trees; our best-known species is 

 the following one. 



The pigeon horn-tail, Tremex coliiniba. — The larva of this species 

 infests maple, elm, apple, pear, beech, oak, and sycamore. The female 

 (Fig. 1 136) in order to oviposit pierces the wood of a tree to the depth 

 of 10 to 12 mm; the eggs are laid singly; sometimes her ovipositor 

 gets wedged in the wood and holds her a prisoner until she dies. 

 The larva is cylindrical and attains a length of 40 mm. It transforms 

 within its burrow, in a cocoon made of silk and fine chips. 



R4.S + M^ 



+ CMi+2 + lat + 2d + SaJi 



.^'-* + Jff, 



Fig. 1 137. — Wings oi Sirex juvencus. (From Bradley.) 



The adults of this species vary in color and marking; based on 

 these variations, three fairly distinct races have been recognized, 

 which to a considerable extent are geographical, although their 

 ranges overlap. In the typical form, race coluniba, the abdomen is 

 black, with ochre-yellow bands and spots along the sides; this is the 

 common form in Quebec, Ontario, and the northeastern United States. 

 In the race aureus the ground color of the abdomen is yellow and the 

 markings black; this is the common form in the Rocky Mountains 

 and is found on the Pacific Coast. In the race sericeus the entire 

 body is fulvous, the legs beyond the femora yellow, and the wings 

 dark reddish brown ; this race is found in the southeastern United 

 States and as far north as Pennsylvania and West to Utah. 



Family XIPHYDRIID^ 



The Xiphydriid Sawflies 



This family is composed of a small number of species which are 

 closely allied to the Siricidae but which differ from them in several 



