INVESTIGATION OF LIFE HISTORY. 67 



spring beetles of this species might survive several days if they should 

 fall into ponds, and that they would probably float with the currents 

 and might be distributed quite a long distance in this way, especially 

 if they fell into streams or rivers. 



Length of Life of Beetles. 



Unlike most species of insects, such beetles of the genus Calosoma 

 as there has been an opportunity to study are, as a rule, able to sur- 

 vive two winters and carry on active warfare against caterpillar life 

 during two summers. 



With species whose length of life extends over such a long period 

 it is difficult to secure normal data if they are closely confined, and 

 although the laboratory experiments show that Calosoma sycophanta 

 usually hibernates two winters and sometimes more, it is probable 

 that under normal field conditions even greater length of life could be 

 reasonably expected. An abundant food supply naturally stimu- 

 lates the activities and reproductive capacity of the species, and 

 where such conditions prevail, the insects exhaust themselves more 

 rapidly, and the length of life of the adult is therefore somewhat 

 curtailed. Such evidence as is at hand seems to show that if for 

 any reason the food supply is scanty the majority of the beetles are 

 able to survive, although their activities and rate of reproduction 

 are materially decreased. 



This bears out the observations which have been made at different 

 times on native species of Calosoma which have been found very 

 abundant during local caterpillar outbreaks, although previously 

 they were considered somewhat rare. 



The tables which follow give a summary of the data secured on 

 the length of life of adults fed in captivity at the laboratory. Speci- 

 mens received from Europe enter into this computation to some 

 extent, but of course it is impossible to determine with any degree 

 of accuracy the length of life of such insects, as their previous history 

 is unknown. 



A record is given of the length of life of seven examples, 3 males 

 and 4 females. These, with several others, pupated in the fall of 



1907, but the others died, chiefly because unsuitable hibernation 

 quarters were furnished during the first winter. 



Of the 4 females noted above, all of which were supplied with males 

 during the summer of 1908 and 1909, 1 fed during the summer of 



1908, laid no eggs, and died in hibernation during the winter of 

 1908-9; 2 fed during the summers of 1908 and 1909, laid eggs the 

 latter summer, and died August 10 and 26, 1909. The remaining 

 female fed during the summers of 1908, 1909, and 1910, laid eggs the 

 first and third summers, hibernated three winters, and died August 

 1 ? 1910. Of the 3 males, all of which were placed in jars with 



