Oct. 22, I92I Hopkins Host-Selection Principle 211 



the broods. Attempts have been made to start colonies in hickory and 

 white oak. 



HicORiA. Experiment VI ^— March 31, 19 17, seven adults (four 

 females and three males) from ash were isolated on hickory cut Feb- 

 ruary I, 191 7. No infestation occurred. May 31 of the same year 

 fifteen larvae, 2 to 4 mm. long, were transferred to hickory. Again 

 on June 15, seven larvae, 4 mm. long, were transferred to the same 

 piece of wood. July 11 one larva was living and five more, over half 

 grown, were transferred. 



April 6, 191 8, three adults (two males and one female) emerged from 

 the hickory. They were caged on hickory and ash cut January, 19 18. 

 These adults were very weak and inactive, not at all characteristic of 

 normal adults. 



An examination in July showed neither wood to be infested. 



July 24, 19 1 8, twenty larvae, one-half to three-fourths grown, were 

 transferred from ash to hickory cut April 15, 19 18. 



April II, 19 19, one female emerged, one adult had died in its pupal 

 cell, and the remainder of the larvae had died before pupating. This 

 female was mated with a male from ash and caged on hickory and ash 

 of optimum cuts. An examination in July showed no infestation in the 

 hickory, but the ash contained a few larvae. These died later in the 

 summer. 



QuERCUs AiyBA. EXPERIMENT VI ^. — ^April I, 1917, four pairs of 

 adults from ash were isolated on white oak cut in March, 191 7. Eggs 

 were laid on the wood, and the small larvae bored through the bark, but 

 all died before May 31. On this date fifteen larvae, 2 to 4 mm. long, 

 were transferred to white oak. July 1 1 one larva was living. Septem- 

 ber 17 all were dead. 



In April, 19 18, three pairs were caged on wood cut in January, 19 18. 

 July 18 many larvae were still alive but under size. Several lived to 

 pupate, but all died before the following spring. 



Seasoning. Experiment VI. ^ — ^April 4, 19 17, four pairs of adults 

 were isolated on ash cut September i, 19 16, and white oak cut in March. 

 The females laid eggs on the white oak, but the larvae did not live. On 

 Ma7 3 1 neither wood contained larvae. 



CONCLUSIONS 



The foregoing experiments show that this species feeding in ash 

 (Eraxinus) has become decidedly accustomed to that host. Several 

 attempts, both by oviposition and larval transfers, to produce strains in 

 Quercus alba Linn, and Hicoria have resulted in failure. In Hicoria 

 the few adults secured were incapable of continuing the colony, and in 

 both woods a high or total larval mortality occurred. 



Even with this decided preference for a host, the adults laid eggs on 

 a new host rather than on an unfavorable cut of the normal host. 

 65583°— 21 3 



