Oct. 22. I92I Hopkins Host-Selection Principle 215 



adults emerged and only one each of the others. This amount of the 

 original host for two females was considered sufficient for oviposition 

 without bringing in the quantity factor. 



These adults are extremely active and run rapidly over logs when 

 ovipositing in nature. They have very long hind legs. It was noticed 

 that in the glass cylinder used for cages in 19 18 these long legs were a 

 disadvantage. The adults could not get a foothold on the glass and 

 had difficulty in climbing up on the wood from the glass surface. They 

 crawled awkwardly about and when coming in contact with any stick 

 maneuvered until they managed to get on it. Such conditions may 

 have influenced the wood selected, as the adults could only with difficulty 

 go from one stick to another. In 19 19 wire boxes were used, the wood 

 lying flat on the bottom. In 1920 only ash and dogwood strains were 



continued. 



CONC1.US10NS 



These experiments up to 19 19 did not seem to show results in any defi- 

 nite direction. Selections of the various host strains occasionally gave 

 results in conformity with those generally obtained, while again just 

 opposite results were recorded. 



The experiments of 19 19 showed results in closer conformity to those 

 of other species. This may have been due to the different method of 

 caging, which gave the adults more opportunity to move about and select 

 the host. 



UOPUS AIvPHA. EXPKRIMBNTS XXV AND XXX 



Two color forms of Liopus alpha have been experimented with, a brown 

 form from sumac (Rhus) and a gray form from hickory (Hicoria) . These 

 color forms are very distinct and easy to recognize as adults. They are 

 not known from any other hosts. The sumac form has been collected 

 throughout the eastern United States and as far west as the Rocky Moun- 

 tains. The hickory form follows the range of the hickory trees. 



The adults fly in late May and continue flying through June at Falls 

 Chiu-ch, Va. One year is required to complete the life cycle. The larvae 

 feed beneath the bark and pupate in the wood. They are found only in 

 small branches. 



LIOPUS ALPHA, RHUS FORM. EXPERIMENT XXV 



The sumac form prefers branches cut in the early fall and dried standing 

 in the air, although it will attack later cuts, provided they have dried 

 considerably. 



April 26, 1916, Mr. Champlain sent from Long Island, N. Y., a lot of 

 infested sumac twigs which were caged at Falls Church, Va. In June the 

 first adults emerged, and 20 were caged on sumac cut in November, 1915. 

 Into the same cage were placed chestnut, hickory, and wild cherry twigs 

 cut during the winter, but none of these latter woods were infested. Since 

 then it has been continued in sumac. 



