188 Zoology of Colorado 



Insects of Western North America, is I think much to be pre- 

 ferred. There are so many kinds of Hymenoptera that even 

 a brief treatment of the Colorado species would fill a large volume. 

 All we can do here is to call attention to a few of the most in- 

 teresting. 



Sawflies and Horntails (Tenthredinoidea) 



The Horntails (Siricidae) are large parallel-sided insects, the 

 females with a long tail-like ovipositor. They come from larvae 

 boring in the wood of trees. The group is a very ancient one, the 

 oldest known Hymenoptera (from the Mesozoic) being rather 

 closely related to the living horntails. There is a very large 

 ichneumon-fly (Megarhyssa) which is parasitic on the larvae of 

 horntails, and inserts its extremely long ovipositor into the 

 trunks of trees to reach its prey, and there deposit its eggs. Uro- 

 cerus flavicornis Fabricius is a large horntail of the mountains and 

 north. The female is not much less than an inch and a half long, 

 counting the ovipositor. It is black, with two orange bands on 

 the abdomen. It was long ago taken in Boulder Canyon by 

 Putnam, and in Wet Mountain Valley. It is reported from 

 Labrador, and Mrs. Cockerell took it at White Horse in the 

 Yukon. It breeds in coniferous trees. Sawflies (Ten thredinidae) 

 are usually of moderate size, some very small. They have no 

 constricted waist, such as is seen in wasps and bees. The larvae 

 of most species feed on foliage, and are caterpillar-like. One 

 form, introduced from Europe, is the Pear-slug {Eriocampoides 

 limacina Retzius). The slug-like larvae eat the surface from the 

 leaves of pear, cherry and hawthorn, and are very destructive. 

 I have found them on the wild hawthorn at Boulder, a matter of 

 some consequence, as they can survive there, even though de- 

 stroyed in the gardens. Another imported pest is the Currant- 

 worm (Pteronidea ribesii Scopoli), the larvae injurious to currants 

 and gooseberries. In 1906 I found a supposed new species in 

 Boulder, and named it P. arapahonum, but it now turns out it 

 was only a slight color variation of the imported P. ribesii. Still 

 another pest is the small black Caliroa aethiops Fabricius, found 

 on cultivated roses. Dogwood (Cornus) bushes in the grounds 

 of the Court House at Boulder were severely injured by the larvae 

 of Harpiphorus varians Norton. 



