INSECT ENEMIES Oi" WESTERN l-()liESTS 



157 



and there is little danger of these insects attacking dry, finished 

 lumber products. 



The different species of horntails are very difficult to distinguish, 

 and many of the species have not been named or satisfactorily sep- 

 arated. In many cases the males and the females of the same species 

 have been given different names, since the sexes are markedly dif- 

 ferent in appearance. Only a few of the more common ones need 

 be mentioned. 



Figure 78. — Western horntail (Sirex aerolatas) : A, Adult male, X 1.5; B, female, 

 X 1-5 ; C, larva, X 3 ; D^ pupa, X 3 ; /i", exit holes ; F, larval mines. (Edmonston.) 



TJrocerus californicus Nort. is the largest of the western species. 

 The females are dangerous-looking wasps with black bodies and 

 legs, yellow antennae, yellow bands on legs, patches of yellow on 

 sides of head, and amber wdngs. They measure from 1 14 to 2 inches 

 in length, and the ovipositors are slightly shorter than the body. 

 The males are smaller and have yellow bodies. The larvae infest 

 balsam firs and Douglas fir and sometimes pine. Urocerus -flavicornis 

 F. is a somewhat smaller species, 1 to li/4 inches long, and black, 

 marked with yellow or red. It breeds in various coniferous trees, 

 including the firs and pines. 



Sirex californicus Ashm., a dark, metallic, blue-bodied species 

 with buff -colored wings and black legs, is commonly found infesting 

 pines. S. juvencus L. is also metallic blue, but the legs are dark 



