INVESTIGATION OF LIFE HTSTOEY. 57 



The beetles in the above experiments remained a portion of the 

 time under the earth during the first two weeks, but from that time 

 until they died were always to be seen on the surface at any hour 

 during the day. 



Table XIII shows that the Calosoma beetles can survive for a 

 month without food, and under natural conditions in the field, where 

 more or less moisture is present, the length of time would no doubt 

 be increased. Apparently old beetles can withstand starvation better 

 than young beetles, and males appear to die sooner than females, 

 under these conditions, but several exceptions are to be noted in the 

 table. The number of specimens under consideration is not large 

 enough to give more than a general idea of the hardy nature of this 

 species. 



A field colony of Calosoma beetles was liberated in 1907 with the 

 idea of testing their ability to survive on a very limited food supply. 

 On August 28, 50 specimens, 25 of each sex, were liberated in wood- 

 land in Peabody, Mass. These beetles had been received from 

 Europe during the month and had been supplied with very little food 

 since they arrived. At the date of liberation there were no gipsy 

 moth caterpillars in the field and very few pupae. Occasionally a 

 native caterpillar would be seen, but they were rare in the vicinity of 

 the colony. Under these conditions it appeared possible to make a 

 thorough test. 



The colony was examined the next spring and summer. On July 

 8 a Calosoma larva was found, showing that reproduction had taken 

 place. This would indicate that the species can survive under very 

 unfavorable conditions. 



Assembling Experiments. 



In the summer of 1910 it seemed desirable to carry on a few experi- 

 ments to determine, if possible, the distance that the male Calosoma 

 beetles are attracted by the females, and for tins purpose a cage was 

 set up in the salt marshes between Lynn and Revere, Mass. This 

 cage (fig. 20) was about 10 inches square and 12 inches high. The 

 sides were covered with mosquito netting and underneath a narrow 

 board which extended around the cage, and which was beveled on the 

 underside, was stretched a thin sheet of rubber, which was attached 

 in such a way that beetles from the outside could gain admission but 

 could not escape. Within this cage was placed a wire cylinder con- 

 taining both old and young females which had just emerged from 

 hibernation. 



June 13, 1910, this cage trap was set up in the marsh at a point 

 one-half mile or more distant from any trees. It was attached to a 

 pole about 8 feet high, and in the inner cage were 2 young and 2 old 



