INVESTIGATION OF LIFE HISTORY. 



43 



molted twice in the jars. The mortality for the season of 1909 was 

 10 per cent of the 8,280 larvae which were fed in this way, and for 

 1910 it reached 12 per cent of the 8,720 larvae that hatched. It is 

 interesting to compare these figures with those for the year 1908 when 

 a smaller number of larvae was fed individually in jelly glasses 

 provided with cheesecloth covers. A considerable number of larvae 

 escaped by forcing their way through the covers and in all 13.8 per 

 cent of the total for the year (2,854) were either lost or died. This 

 shows that the improved covers used on jars the following years and 

 the experience gained in handling the larvae have resulted in reducing 

 the mortality. 



Since the work began, July 23, 1907, nearly 20,000 Calosoma 

 larvae have been cared for and most of these have been liberated in 

 the field. 



In August, 1909, a considerable stock of Calosoma larvae was on 

 hand at the laboratory, and as it seemed advisable to feed and carry 

 them through the 

 larval stages and 

 hibernation where 

 they could be under 

 direct observation 

 they were placed in 

 large box cages (see 

 PL V) set in the 

 ground. These were - 

 2 by 3-J feet in size, 

 and were provided 

 with a fine wire- 

 netting bottom so 

 that the larvae could 

 not escape. The 

 earth in the cages 

 was 15 inches deep, 

 inches in diameter, 



Fig. 18. — Wire-screen hibernation cylinder where larvae of Calosoma 

 were fed in August, 1910. Photographed February, 1911. (Original. ) 



Several cylinders of galvanized iron wire, 17 

 were also constructed for the same purpose 

 and were sunk in the ground and later stocked with larvae and food. 

 (See fig. 18.) These cylinders were lined on the inside with mosquito 

 netting and the tops and bottoms were made of the same material. 



One thousand three hundred and eight second and third stage 

 Calosoma larvae were placed in these cages or cylinders between July 

 30 and August 27, 1909, and of this number 210 larvae, or 16.6 per 

 cent, were killed by their comrades. The food supply was of necessity 

 very poor in quality, especially after the middle of August when 

 gipsy moth larvae and pupae that had been held in cold storage were 

 furnished, many of which were in a badly decomposed condition. 



