INVESTIGATION OF LIFE HISTORY 



53 



into hibernation, and, as a rule, the beetles are rather sluggish in 

 movements. 



Many records have been secured, but the most typical are perhaps 

 the ones obtained during the summer of 1910. Twelve pairs of 

 Calosoma beetles were kept under observation, being fed in jars. 

 There were 4 pairs of old beetles, the same number of young beetles, 

 old males and young females, and old females and young males. 



The earliest emergence was noted on May 25 and the latest on June 

 5. Feeding was completed between July 5 and August 9. The short- 

 est feeding period was 32 days and- the longest 66 days, with 50 days 

 as an average. 



The feeding period corresponds fairly well with that of the cater- 

 pillars of the gipsy moth. The beetles do not emerge at quite as 

 early a date in the spring as that upon which the gipsy moth cater- 

 pillars hatch, and in the fall the gipsy moth has transformed and 

 deposited its eggs before the Calosoma beetles seek hibernation. 



Food of the Adults. 



The food of the adult beetles is similar to that of the larvse. Each 

 year some of the Calosoma beetles have been fed on native lepidop- 

 terous larvse and none of the species offered was rejected by them. 



If the weather is cool in the early summer, the beetles remain on 

 the ground, usually under leaves or litter, and sally forth on the 

 first warm days in search of food. As soon as caterpillars become 

 scarce, late in July or early in August, the beetles feed less and 

 spend most of the time beneath the ground, soon burrowing down to 

 form the hibernating cell. 



Elaborate experiments have been conducted each year since 1907 

 to determine the number of gipsy-moth caterpillars that are destroyed 

 by these predaceous beetles and a mass of data has accumulated 

 from which typical results have been selected. The most complete 

 series of experiments was conducted during the year 1910, and the 

 results are summarized in Tables X, XI, and XII. 



Sixth-stage tent caterpillars and gipsy-moth caterpillars were used, 

 as they were of about the same size and offered a fairly uniform 

 ration on which to base the average amount of food consumed. 



Table X. — Feeding records of 4 pairs of young Calosoma beetles, 1910. 



Pair No. 



Emerged 

 from hi- 

 berna- 

 tion. 



Ceased 

 feeding. 



Sixth-stage caterpillars 

 consumed. 



Tent. 



Gipsy 

 moth. 



Total. 



4804 



May 26 

 ...do 



July 15 

 ...do... . 



76 

 135 

 120 



60 



165 

 39 



226 

 35 



1241 



4805 



174 



4800 



...do 



July 13 

 July 8 



1346 



4807 



...do 



95 









Females laid eggs. 



