60 



CALOSOMA SYCOPHANTA. 



The data secured from observations made in field colonies indicate 

 that in many of these where beetle larvae we're liberated it has been 

 possible to find excellent reproduction the next season. It is prob- 

 able that under natural conditions the average number of eggs laid 

 by all female beetles in the field, regardless of age, will be about 100. 



Young beetles do not lay as many eggs the first season as those 

 beetles that are a year older; in fact it appears that a certain propor- 

 tion of the young females does not oviposit at all the first season. 



Table XV gives the results of a series of experiments carried on 

 during the summer of 1910. It shows the difference in the egg-laying 

 habits between the young and the old beetles and indicates the relation 

 between active oviposition and food consumption. 



Table XV. — Difference in the egg-laying habits between young and old beetles of Calosoma 

 sycophanta and relation between active oviposition and food consumption, 1910. 



No. 



Cater- 

 pillars 

 eaten. 



Larvae 



pro- 

 duced. 



No. 



Cater- 

 pillars 

 eaten. 



Larvse 



pro- 

 duced. 



Young beetles: 



4804 



241 



174 



346 



95 



61 

 



31 

 



Old beetles: 



4808 



305 

 289 

 290 

 328 



191 



4805 



4809 



44 



4806 



4810... 



317 



4807 



4811 



97 





Average 







214 



23 



303 



162 









It will be noted that the old Calosoma beetles ate more gipsy-moth 

 caterpillars and laid many more eggs than the young female beetles, 

 50 per cent of which did not reproduce. The following year these 

 beetles will oviposit freely, as has been repeatedly shown in the 

 previous work. 



In order to ascertain whether any difference would result in breed- 

 ing old males with young females and vice versa, 4 pairs of beetles 

 were tested and the results are given in the following table : 



Table XVI. — Results of breeding Calosoma sycophanta: (1) Old males and young 

 females; and (2) young males and old females. 



Pair No. 



Cater- 

 pillars 

 eaten. 



Larvse 



pro- 

 duced. 



Pair No. 



Cater- 

 pillars 

 eaten. 



Larva? 



pro- 

 duced. 



Old males, voung females: 



4812 



216 



188 





 



Young males, old females: 

 4814 



461 

 230 



155 



4813 



4815 



0) 







1 Eggs laid, but did not hatch. 



The results shown in Table XVI should not be considered as con- 

 clusive owing to the small numbers of beetles used. It has occa- 

 sionally been observed that young females reproduce when placed in 

 jars with old males, and that the old females when kept in captivity 

 with young males sometimes fail to do so. 



