THE CALOSOMA BEETLE IN NEW ENGLAND. 13 



the mortality of beetles during the winter runs from 22 to 35 per 

 cent, first-year beetles showing the lowest death rate. 



A large number of experiments were carried on in the spring of 

 1908 to determine whether it would be possible to induce this species 

 to develop more than one brood in a single year. Beetles were re- 

 moved from hibernation on March 4 and were fed in jars at the 

 laboratory. Difficulty was experienced in securing a sufficient food 

 supply, but the beetles did not feed at all freely and were rather 

 inactive in the jars. Eggs were deposited a little earlier in the season 

 than was the case when the species emerged normally, but the larvae 

 grew very slowly and did not develop much earlier than those which 

 resulted from beetles that emerged early in June. The experiment 

 indicated very conclusively that it was not possible to force this 

 species and that the habit of developing a single generation a year 

 is firmly fixed. 



FEEDING HABITS OF ADULTS. 



The beetles climb trees readily and travel out on the branches and 

 sometimes cling to the leaves while searching for caterpillars. If 

 disturbed they usually fall to the ground and immediately seek shelter 

 underneath leaves or rubbish. The beetles usually seize the cater- 

 pillars in the middle of the back and cut through the body wall with 

 their sharp mandibles. They feed upon the liquids and fatty mate- 

 rial which form the body content of the caterpillar and usually injure 

 many more than they actually devour. The average length of time 

 during which the beetles feed is from about June 1 to July 15. From 

 records secured in 1910 the shortest period of feeding was 32 days 

 and the longest 66 days, with an average of 50 days. These records 

 were secured from beetles kept in captivity. It will be noted that the 

 time when the beetles are feeding corresponds roughly with the time 

 when the gipsy moth is in the larval stage. This makes this beetle 

 particularly adapted for feeding on the gipsy moth, and a further ad- 

 vantage results from the fact that the larvae of Calosoma sycophanta 

 are most active during the time the gipsy moth is in the pupal stage. 

 The food of the adults is very similar to that of the larvae ; both are 

 frequently found in the field feeding upon larvae and pupae of native 

 Lepidoptera. 



It is difficult to determine the number of caterpillars which are 

 destroyed by a single beetle. This can only be done by feeding the 

 beetles in captivity ; and under these conditions they evidently do not 

 destroy as many caterpillars as they would if they were living in the 

 open. Experiments which have been conducted, using full-grown 

 tent caterpillars and gipsy-moth caterpillars, showed that the average 

 number of caterpillars destroyed by an old beetle was 328 and by 

 young beetles 239. The young beetles — that is, those that are feeding 



