INVESTIGATION OF LIFE HISTORY. 61 



It is evident, however, that greater reproduction takes place with 

 old female beetles than with young ones, whether they are attended 

 by young males or old males. 



Some curious results of rearing experiments are given in Tables 

 XVII and XVIII, which were prepared to show the length of life of 

 adults of this species. Apparently it is the habit of these beetles to 

 oviposit sparingly the first summer and freely during the second sea- 

 son. If conditions are very favorable the first year, a considerable 

 number of eggs may be laid, while if they are unfavorable oviposition 

 is postponed to the second or third summer as the case may be. It 

 sometimes happens that eggs are laid the first and third summers, 

 but not during the second; at any rate each female will lay about 

 the same number of eggs, but the time when they are deposited 

 varies greatly. 



The data secured from field colonies bear out these facts. Two- 

 thirds of the larval colonies have shown some reproduction the year 

 following the planting, but in most cases the rate was very small, 

 indicating that only a small proportion of the females laid eggs. By 

 comparing the number of molted larval skins found in an adult 

 colony in Wellesley, Mass., in 1908, and those secured in the larval 

 colonies the year following their planting, it appears that the adult 

 colony of old beetles reproduced thirteen times as rapidly as did the 

 larval colonies during the year following their liberation. This may 

 be explained in part by the greater tendency of the young beetles to 

 disperse owing to scarcity of food or other natural causes, but it is 

 evident that they reproduce much more slowly. The jar records 

 indicate (see Table XV) that the old beetles multiply seven times 

 as fast as young ones and an average in the field of 10 to 1 in favor 

 of the old beetles would probably be about right. 



Polygamy. 



It has often been observed that females mate with the males several 

 times during the summer and it is probable that this is necessary in 

 order to insure the fertility of all the eggs. 



Nearly every year several jars have been kept under observation 

 where a single male was confined with 2 females and no cases have 

 been noted where infertile eggs were deposited. In the summer of 

 1908 a record was kept of two jars, each containing a male and 3 

 female beetles. The insects fed voraciously and at the close of the 

 season 306 eggs had been laid in one jar and 618 eggs in the other one, 

 all of which hatched. 



The average for each female in the first jar was 102 eggs and in the 

 second 206 eggs, both of which are above the normal. 



Although it is not known positively that each female in these jars 

 laid eggs, it is probable that this was the case, owing to the large 



