36 CALOSOMA SYCOPHANTA. 



Table VII. — Food eaten by larva; of Calosoma sycophanta. 



The larvae in Table VI required on an average 28 days to complete 

 their feeding, while in Table VII only 14 days were necessary. The 

 number of caterpillars consumed in the first was considerably greater 

 than in the second series. This was largely due to the fact that those 

 in the second series were fed entirely on sixth-stage gipsy moth cater- 

 pillars, while the other lot was furnished with smaller caterpillars for 

 food. The average given in Table VII is probably the inore correct 

 index of what takes place under natural conditions in the field, and 

 it shows that on the average a single larva of Calosoma sycophajita 

 will destroy at least 41 full-grown gipsy moth caterpillars. The 

 results shown in these two tables illustrate how impossible it is to 

 attempt to accelerate the development of certain species of insects. 

 Wliile some of the parasitic forms will reproduce as long as a proper 

 food supply is maintained and the temperature kept above a point 

 where they seek hibernation, it has been impossible to induce the 

 beetles of this genus to depart from tlieir fixed habit of developing 

 only one generation in a single year. 



EXPERIMENTS IN FEEDING CALOSOMA LARV^ WITH DISEASED GIPSY MOTH 



CATERPILLARS. 



The question is often asked whether the larv^ of this species are 

 susceptible to the disease commonly known as the ''wilt," wliich each 

 year destroys enormous numbers of gipsy moth caterpillars in badly 

 infested colonies. In order to make a test, a limited number of 

 experiments was carried on both in 1908 and 1909 The results in 

 1908 seemed to indicate that the larvae suffered very little from this 

 trouble, and in 1909 the tests were continued, but unfortunately the 

 larvae were fed in jelly glasses which proved too small to allow them 

 to move freely after they became nearly full grown. The final results 

 were similar to those secured the previous year, but it was thought 

 best to make a further test in 1910. Ten larvae that hatched on June 

 30 were fed in individual jars with gipsy moth caterpillars that showed 

 signs of the "wilt." Feeding continued until July 15. One larva 



