268 WEST VIRGINIA EXPERIMENT STATION. 



have often seen, literally swarm around small trees infested by 

 this class of bark miners. 



The habit of the Chalcid larva is similar to that of the 

 Braconid, that is most of them which attack bark mining grubs 

 are external parasites, but unlike the Braconid, they rarely 

 make cocoons, but instead, undergo their transformation in the 

 cavity left by their victim. The adult bark beetles are also at- 

 tacked by Chalcid parasites, in which case the Chalcid lives in 

 the abdomen of its victim. 



See list of Chalcids in Appendix for reference to habits of 

 species. 



TACHINID PARASITES. 



It is common for two-winged flies to attack caterpillars and 

 the adults of insects which live in the open air, but it is not 

 common for a fly to attack bark and wood raining insects. In 

 fact there appears to be but few records of their doing so. It is 

 the habit of this class of parasites to glue their eggs to the sur- 

 face of the body of other insects. These eggs hatch into min- 

 ute maggots, which burrow into their host and feed upon the 

 liquids. The adults are not provided with horny ovipositors as 

 are the three classes of parasites above mentioned, so it would 

 seem difficult and almost impossible for any of this class of 

 parasitic insects to attack the larvae of bark beetles, yet I have 

 found the larvae and cocoons of a small fly (Medeterus nigripes* 

 Leow) so common in the larval mines of the destructive spruce 

 bark beetle that there appears to be no doubt of its being a 

 primary parasite of the larvae of this beetle ; but how and 

 where the eggs are deposited, and how the minute, slender 

 maggot finds its way to the bark mining grub, I have not as yet. 

 been able to determine. 



Another undetermined Dipterous larva was also commonly 

 found associated with the larvae of the spruce bark beetles in 

 such a manner as to indicate that it was an enemy of this class 

 of bark miners. 



DISEASES OF INSECT EMEMIES OF THE SPRUCE. 



Both the bark and wood mining insects, adults as well as 

 larvae and pupae, are subject to attack by fungus diseases, and 



