2o6 Journal of Agricultural Research voi. xxn. No. 4 



A colony can be produced in a host which is in an unfavorable condition, 

 but the resulting adults are below normal size. Owing to the failure to 

 continue the colony it can not be stated whether or not such a strain 

 would show preference for the new condition of the host by selecting it 

 voluntarily. 



CALLIDIUM JANTHINUM. EXPERIMENT V 



Under Callidium antennatum reference was made to C. janthinum 

 Lee. It is distinguishable from the former by its smaller size, shining 

 surface, and bluish green color of the adult, by the fact that the larva 

 feeds only in juniper, and that the adults emerge about four weeks later 

 in the spring. It requires wood which was cut during the late fall and 

 which has not seasoned in contact with the ground. It will oviposit in 

 greener wood than C. antennatum although the inner bark should not 

 be sappy. 



The first flight occurs during the first to third week in May and con- 

 tinues about two weeks. One year is required to complete the develop- 

 ment. The larvae feed beneath the bark until half grown, then excavate 

 long pupal chambers, the ends of which are plugged off for the trans- 

 formation cell. 



These experiments were started with a lot of infested juniper branches 

 from Hummelstown, Pa., collected by J. N. Knull in April, 1916. May 2, 

 six adults emerged and were caged on juniper cut in April and rapidly 

 dried in the house. Since then the colony has been continued each 

 year in September and November cuts of juniper, which are preferred. 



PiNUS. Experiment V^ — May, 191 7, two pairs were isolated on pine 

 cut in November, 19 16. A few eggs were laid from which larvse hatched 

 and entered the bark. By July 10 all had died. The same test was 

 repeated in 19 18 with similar results. 



CONCLUSIONS 



This species shows a decided preference for jumper and will not develop 

 in pine from early stages. Larval transfers to pine with nearly matured 

 larvae were not made. 



CAIvWDIUM ANTENNATUM AND C. JANTHINUM. VXIV; IV XV 



Because of the taxonomic confusion between these species (cited pre- 

 viously) and with the idea that a crossing of these two forms might possi- 

 bly influence the selection of a host, attempts were made to cross the 

 species. 



VxIV. — In May, 19 17, four females of the juniper form were crossed 

 with two males of the pine form and were caged on juniper. Both 

 species had been previously isolated from the pupal cells to avoid all 

 possibility of mating. These insects immediately mated, and the eggs 

 were laid on the juniper from which a good infestation was secured. 



