Oct. 22, 1921 Hopkins Host-Selection Principle 1 93 



and the exact conditions required, have been used in confining the colonies 

 of beetles. It is essential to duplicate as closely as possible the conditions 

 in which the insects are found in nature. 



For the larger logs and for experiments in which a large amount of 

 material was used, an open wire insectary was constructed. This 

 insectary is 40 feet long by 10 feet wide by 7 feet high. The foundation 

 is of concrete, the side walls and top of i8-mesh galvanized wire screening, 

 and over all a removable lattice- work roof was placed. This roof was 

 adjusted to simulate shade conditions in the woods. It was removed 

 in winter and replaced in summer. The floors were made of ashes to 

 give good drainage. Cross partitions divided the insectary into seven 

 compartments of different sizes. One room was entirely boarded in 

 and roofed over. It was used for seasoning wood. Another was lined 

 with cheesecloth, which was used for holding different cuts of wood under 

 natural conditions until desired for use. In the other compartments 

 were placed logs containing various species of insects. Where no danger 

 is present of any infestation from the original host wood into cuts of 

 different wood, it was possible to place several beetle species in the same 

 compartment and continue their breeding in the same host from year to 

 year. In this way forms such as Callidium in pine {Pinus spp.) , Neodytus 

 capraea Say in ash {Fraxinus spp.), and Cyllene pictus Drury in hickory 

 {Hicoria spp.) were placed together. 



The smaller insects, especially those in twigs and branches, were 

 confined in glass museum cylinders of various sizes. The tops were kept 

 in place so that a very constant degree of humidity could be maintained. 

 This cage was found to give best results for the development of the larvae 

 and, as no sand was needed, the adults were easily found in the cages. 

 These jars were kept under a roof all the year in another insectary. 



Each of these insects has a particular preference for a certain condition 

 or seasonal cut of wood. Also in some species the adults require food 

 before ovipositing, consisting of green bark from twigs, leaves, or fungus 

 s'pores. In the latter case the pustule of the chestnut blight {Endothea 

 parasitica (Murr.) P. J. and H. W. Anderson) was used. Again, some 

 require much moisture, others rather dry surroundings. The determi- 

 nation of these factors sometimes delayed the successful continuance of 

 a species for a year or more. When a new colony was collected from 

 nature it was ascertained as nearly as possible when the tree died and the 

 condition of the wood, also what degree of humidity was desirable. For 

 instance, those insects naturally feeding in dead branches of a standing 

 tree required drier conditions than those attacking branches fallen to the 

 ground. 



In order to meet these conditions, wood of the various species used was 

 cut every month or every other month of the year and stored under 

 different conditions. Part was placed in the dry shed for dry seasoning, 

 part hung or stood up in the open-air cage for normal air seasoning, and 



