THE GENUS CALOSOMA. 9 



For instance, if caterpillars and pupae of Malacosoma americana and 

 Euproctis chrysorrhoza were the only source of food for 0. sycophanta 

 in New England it is very probable that the beetles would increase 

 very slowly if at all. The adults of Calosoma emerged from hiber- 

 nation at Melrose Highlands, Mass., in 1910, between May 11 and 

 June 28, the average date being June 2. 1 Usually a week or more 

 intervenes before active egg deposition begins, and it is about June 

 15 before the eggs begin to hatch. The Calosoma larvae that hatch 

 from the first eggs deposited usually find ample food in the cater- 

 pillars and pupae of M. americana, large, full-fed caterpillars of E. 

 chrysorrhoza, and a little later the pupae of this species. The supply of 

 Malacosoma for food purposes is practically exhausted by June 25, and 

 that of Euproctis by July 15. Between these dates the most active 

 reproduction of C. sycophanta takes place under present conditions, 

 and it is evident that the bulk of the larvae would die from starva- 

 tion if other food were not available. On the other hand, the habits 

 of this beetle and its larvae are so well adapted to those of the gipsy 

 moth that it seems impossible for any other species of Calosoma to 

 fare better on this particular prey. 



Cannibalism among the larvae of the various species is also no 

 small factor in limiting the increase. All the species reared at the 

 laboratory and further treated in this paper possess this habit in the 

 larval stage. Irreparable losses have resulted in laboratory ex- 

 periments when attempts were made to feed from 8 to 15 larvae in a 

 battery jar with 2 to 3 inches of moist earth in the bottom. As 

 soon as the food supply was nearly exhausted the larvae began to 

 attack one another. (PL II, C.) Despite the large number of syco- 

 phanta larvae reared for colonization work in New England, it was 

 impracticable to feed many of them together for more than from 

 four to six days after hatching, as the mortality in captivity became 

 too high. After these larvae reached the second stage the mortality 

 rapidly increased from this cause. Cannibalism does not appear 

 to be of special importance under field conditions unless the food 

 supply is greatly restricted. 



The ability of Calosoma larvae to climb into the trees is an impor- 

 tant factor. Many species are unable to do this and it is therefore 

 impossible for them to feed upon arboreal lepidopterous larvae. 

 Species of Calosoma larvae that are able to climb are thereby en- 

 abled to increase more rapidly and are of greater economic impor- 

 tance except in cases where the habits of the host are strictly terres- 

 trial. 



EXPERIMENT TO DETERMINE THE CLIMBING HABITS OF CALOSOMA 



LARVAE. 



A small white oak tree was cut during the spring of 1911 and two 

 sections of it, each 6 feet 5 inches long and about 3| inches in diam- 

 eter, were set upright in a cage at the laboratory so that a study 

 might be made of the climbing habits of the various species of Cal- 

 osoma. The sections of the tree were held in place by wires attached 

 near the top, and the base, which rested on the cement floor of the 

 cage, was encircled by a strip of tin 4 inches high. This inclosure, 



1 Burgess, A. F. Calosoma sycophanta. U. S. Dept. Agr. Bur. Ent. Bui. 101, 94 p. (p. 48), 9 pi., 

 22 fig. 1911. 



