386 WEST VIRGINIA EXPERIMENT STATION. 



upon the distribution of the different species. 



NATURAL ENEMIES. 



The Scolytids have numerous natural enemies including in- 

 sects, diseases, birds, and unfavorable climatic and other con- 

 ditions. The insect enemies may be classed under three gen- 

 eral heads: namely, predaceous, parasitic, and robbers. 



PREDACEOUS ENEMIES. 



Numerous species of beetles and their young prey upon bark 

 and timber beetles, among which the Clerids (Family (Jleridae) 

 probably holds first rank; the adults feeding on the adult Scoly- 

 tids, and the larvae on the eggs, larvae, pupae and recently de- 

 veloped adults. In the families Staphylinidae, Colydiidae^ 

 Histeridae, and Tenebrionidae, there are numerous species 

 which enter the broad galleries of different species of Scoly- 

 tids and feed upon the eggs and young larvae. I have observed 

 a small, reddish and black bug; (Hemiptera) inserting its beak 

 beneath the elitra of a timber beetle, G. materiarius, which 

 died within a few minutes after. This insect is frequently met 

 with in the galleries of Scolytids, and it evidently destroys 

 many of the beetles. There are also certain Dipterous larvae 

 which attack and destroy the larvae and pupae of bark and 

 timber beetles. 



PARASITIC INSECT ENEMIES. 



In this class of insects the Scolytids have a host of 'enemies, 

 belonging principally to the Hymenoptera, and the families 

 Braconidae^ Chalcididae and Proctotrypidae. These are small, 

 four winged gnats which pierce the bark with their long ovi- 

 positors or enter the galleries and deposit their eggs with, or 

 into the larvae and pupae of the bark beetles, which are de- 

 stroyed by the little maggots hatching therefrom. The adults 

 are also attacked by this same class of four winged parasites, 

 which develop within the body of the beetle and emerge from a 

 hole gnawed by them through the hard elitra or wing covers. 1 



II have bred three parasites representing different species, from adult Scolytids; 

 one from Pityophthorus minutissimns, one from Tomicus cacographus the other from 

 Polygraphus ruflpennis. See list. 



