12 BULLETIN 251, U. S. DEPARTMENT OF AGRICULTUKE. 



of the following spring. Many experiments have been tried in an 

 attempt to force early emergence and with an idea of breeding this 

 species during the winter in the laboratory, in order to increase the 

 supply for liberation in the field. Efforts along this line have been 

 futile. The species seems to have a well-fixed habit of winter hiber- 

 nation, and apparently requires a long resting period. It is difficult 

 to secure proper food for beetles that may be taken from Liberation 

 during the winter, but, even if this could be obtained, no satisfactory 

 way has been found to increase the number of broods annually. 



THE ADULT OR BEETLE. 



As has been previously stated, the beetles emerge about the first 

 of June. The exact time varies slightly from year to year, depend- 

 ing upon the weather conditions. Beetle larvae that transformed to 

 pupae and remained as beetles in the pupal cavities during the winter 

 emerge at this time as well as other beetles that developed from 

 larvae in previous years. In July after the adults have finished 

 feeding they burrow into the ground and form a cavity in which 

 they remain the next winter. The distance beneath the surface 

 varies greatly and depends to some extent on the looseness of the 

 soil which they enter. They seldom go below the frost line, and. 

 this being the case, the earth around them is usually frozen solid 

 during the winter. The males and females enter hibernation about 

 the same time, but the former usually emerge a day or two earlier 

 in the spring. A few cases are on record where beetles have re- 

 mained dormant in the ground continuously for nearly two years. 

 In one instance a pair of beetles entered hibernation on July 28, 

 1910, and did not emerge from the ground imtil June, 1912. Sev- 

 eral cases of this sort have been found as a result of careful notes 

 from breeding experiments kept at the laboratory. In every case 

 where this has occurred the beetles concerned were more than a year 

 old. In no case have beetles failed to emerge the spring following 

 their development from the larvae. In connection with the hiberna- 

 tion of this species, it should be said that the beetles habitually live 

 in that stage more than one year. As a rule they live for two years 

 and several records indicate that it is not uncommon for them to 

 remain in the beetle stage for three years. A record of one experi- 

 ment shows that several females lived more than four years. Records 

 kept at the laboratory indicate that the percentage of mortality 

 during hibernation is rather high. It should be remembered that 

 these beetles were placed in hibernating cages in the laboratory yard, 

 and although here natural conditions are approximated as nearly as is 

 possible, the location was not quite as suitable as if the insects had 

 had an opportunity to make their own selection. In our experiments 



