INSECT ENEMIES OF EASTERN FORESTS 605 
sitized, but a great variety of hosts are selected and many Coleoptera 
are attacked. With the exception of certain Alysiinae, practically all 
the species of the family are primary parasites. Most of the species 
are small to moderate in size. Various workers have grouped them 
into about 20 different subfamilies. 
Lysiphlebus testaceipes (Cress.) is a common parasite of a number 
of species of aphids throughout the United States. Among others, 
it attacks Myzus cerasi, which feeds on black cherry and other tree 
species. The adult is a small black insect, a little less than 149 inch 
long, with yellowish legs except the posterior pair, which are marked 
with black. The adult female oviposits directly into the body cavity 
of the aphid. Usually only one egg is placed in an aphid, but in any 
case only one parasite develops. When about to pupate, the Lys¢phle- 
bus larva makes a ventral fissure in the body wall of its host and 
cements the latter down, applying a thin film of silk. It then pupates 
within the aphid’s body, using the body wall in leu of a cocoon. 
After transformation the adult chews a circular hole through the aphid 
cuticle just large enough to crawl through. During August and Sep- 
tember about 2 weeks are required for the development of a complete 
generation, therefore a number of generations develop each season. 
The parasites, however, are usually inactive at temperatures below 
56° F. The winter is spent as larvae or pupae within the dead and 
dried body of the host. 
Coeloides dendroctoni Cush. is the most important parasite of the 
mountain pine beetle (Yendroctonus monticolae) in lodgepole pine 
in western Montana and western white pine in eastern Washington 
and Idaho. De Leon (130) discusses the insect’s morphology, and 
gives an excellent account of its biology (157). During the course of 
his studies from 1928 through 1930, parasitization of )). monticolae 
by Coeloides averaged 4 to 32 percent, depending on the age of the 
infestation, and in individual trees it frequently reached 90 percent. 
The adult insect is about 14 inch long. The head, thorax, and legs are 
largely black, while the abdomen is mostly testaceous. It spends the 
winter as a full-grown larva or prepupa within a cocoon spun beneath 
the bark in the host larva’s mine. Pupation takes place in May and 
June and the adult Coeloides emerge in June. The females fly to a 
tree that was attacked by beetles the previous August and contains 
beetle larvae more than half grown. They tap the bark hghtly with 
their antennae to locate a host larva, and then drill directly through 
the bark to pierce the larva and paralyze it. 
The egg is laid on the beetle larva and the parasite larva feeds 
externally. Development is completed, and a cocoon is spun usually 
within 2 or 3 weeks. Most of the Coe/oides remain in the cocoon stage 
until the next year, but a few (about 5 percent) emerge and complete 
another generation. The efficiency of the parasite is low, however, 
probably because the main generation of Coeloides remains in the 
dead trees nearly a year after the host has left, and is thus slow in 
catching up with the host population. 
Phanomeris phyllotomae Mues. is a parasite of Phyllotoma nemo- 
rata, the birch leaf-mining sawfly. It was successfully introduced 
into this country from Europe in 1931-34, and has become established 
in Maine. In Europe it was relatively unimportant as a control fac- 
tor, except in a restricted area, but it was second in importance among 
