ROUSTDHEADED APPLE-TREE BORER. 29 



NATURAL ENEMIES. 



Possibly no other economic insect of equal importance has had so 

 few natural enemies recorded definitely and specifically as has the 

 rounclheaded apple-tree borer. In all the literature upon this borer, 

 there seems to be only one original reference to such an enemy, this 

 being the single instance of the hymenopterous parasite Cenocoelius 

 populator Say, reared about 30 years ago by Riley and Howard 

 (3, p. 59) from borers of this species received from Indiana. Felt 

 and Joutel (6) state that an undetermined carabid larva was found 

 preying on the borers by Walsh and Riley, and practically all ob- 

 servers have noted that woodpeckers are an important enemy, 

 although in no case is the specific identity of the bird or birds 

 established, so far as the records show. 



In rearing and handling many thousands of the borers in various 

 localities the writer has never found any evidence of hymenopter- 

 ous parasites. In two instances undetermined carabid larvee were 

 found devouring young borers in West Virginia and another half- 

 grown borer was found that had been killed by a hairworm, sections 

 of the worm being found in the burrow entwined around and within 

 the dead and shriveled body of its host. A large spider was seen 

 to pounce upon and bite in the back a female beetle that had just 

 issued from her exit hole in a tree. In an effort to rescue the beetle 

 the spider was crushed beyond recognition. The beetle died a few 

 hours later from the wound. 



WOODPECKERS. 



. While the control effect of parasites and predacious insects on this 

 borer is negligible, woodpeckers play an important part in holding 

 it in check. Wherever the writer has collected specimens or made 

 observations in borer-infested localities the work of these birds has 

 always been in evidence. Soon after the borers hatch the wood- 

 peckers begin to find them beneath the thin covering of bark and 

 thereafter the birds drill for them as long as they are in the tree. 

 In several orchards where counts were made from 50 to 75 per cent 

 of the borers had been destroyed in this way. 



During October, 1915, 24 young borers were collected and planted 

 in furrows gouged out of the wood beneath loosened tongues of 

 bark on the trunk of an apple tree. A week later, when the tree was 

 revisited for the purpose of putting a wire screen around the trunk 

 to protect the borers from birds, woodpeckers had punctured every 

 tongue of bark and removed the borers from beneath. Not one had 

 escaped. In May of the same year, while pupae were being collected 

 from an orchard, a total of 11 pupal cells were found and from every 

 one the occupant had been removed by woodpeckers. In another case 



