SEASONAL HISTORY. 



29 



VARIATION IN THE NUMBER OF EGGS PER CLUSTER. 



Under average conditions the eggs for each oviposition are all laid 

 in a single cluster. In this respect exceptions occur when the female 

 is disturbed in the act of oviposition or when the space is too small to 

 hold all the eggs. On the other hand, it has been frequently found 

 that eggs have been laid side by side by different females, so that 

 from the appearance of the cluster separate depositions could not be 

 told apart. In the breeding experiments clusters containing from 30 

 to 35 eggs have been found quite frequently, and these figures repre- 

 sent, approximately, the average number of eggs per cluster. Table 

 II gives the egg deposition of 16 female beetles. As here there had 

 been interference to some extent, and the beetles had been confined 

 in captivity, the average number of 24 eggs per cluster was compara- 

 tively low. The maximum number of eggs in one cluster was 61 and 

 the minimum 4 (Table III). In the rearing cages the period for 

 each separate oviposition occasionally extended over from 1 to 2 

 days, rarely 3 days; normally, however, the eggs w^ere all laid at 

 once and in a single cluster. 



NUMBER OF SEPARATE OVIPOSITIONS BY INDIVIDUAL FEMALES. 



Different female beetles have displa3^ed considerable diversity in the 

 number of times of oviposition. In the experimental work 8 individ- 

 uals failed to deposit any eggs ; others, as recorded in Table II, ovipos- 

 ited from 1 to 9 times, or, on an average, 4 or 5 times. Similarly, the 

 length of time between each oviposition is variable. An average of 4 

 days elapsed between each oviposition. Often the interval has been 

 only 1 day, while in the other extreme in one case the interval was 15 

 days. (See Table IV.) 



Table IV. — Number of days between ovipositions of the grape root-worm as observed 

 during 1909 in breeding cages at North East, Pa. (Supplementary to Table II.) 



No. of ex- 

 periment. 



Periods between ovipositions. 



Total. 



Aver- 

 age per 

 female. 



I. 



n. 



in. 



IV. 



V. 



VI. 



VII. 



VIII. 



1 



2 



3 



4 





1 



2 













6 

 5 

 14 



2.0 

 5.0 



4.7 













11 



2 























5 



6 



7 



13 



6 

 3 



5 

 2 













24 

 19 



8.0 

 3.8 



4 



3 















8 



9 



10 



11 



12 





3 



2 



3 



3 



2 



1 



5 



22 

 4 

 15 

 13 



2.7 

 4.0 

 3.7 

 2.6 



i 



5 



7 

 2 



3 

 3 











1 















13 



14 



15 



16 



Total 



Average.. 



2 



I 



2 

 1 

 5 

 15 



2 

 4 



\ 



2 



1 

 5 



4 

 3 



3 

 2 



5 



1 



4 



26 

 14 

 16 

 22 



3.2 

 2.0 

 4.0 

 7.3 





















52 



4.0 



53 



4.8 



il 



21 

 3.0 



14 



2.8 



7 

 2.3 



7 

 2.3 



9 

 4.5 



200 



53.0 

 4.07 



