GRAPE-BERRY MOTH IN NORTHERN OHIO. 



17 



of the first-brood moths began before the spring brood emergence 

 ended. This means that moths were emerging practically from 

 grape bloom until grape harvest; the majority of all emergence, 

 however, occurred in two well-defined periods, as shown graphically 

 in figure 2. 



PROPORTION OF SEXES OF FIRST-BROOD MOTHS. 



Table XXIII. — Proportion of sexes of first-brood moths of the grape-berry moth, 



Sandusky, Ohio, 1917. 



Sex of moths. 



Number 

 ofmoths. 



Percent- 

 age of 



sexes. 





316 



1,412 



41 



18.28 





81.72 













Total 



1,769 



100.00 







The high percentage of female moths helps further to explain the 

 occurrence of a large second brood of larvae. 



LIFE CYCLE OF THE FIRST GENERATION. 



Table XXIV. — Life cycle of the first generation of the grape-berry moth as determined 

 from observations on the separate stages; summaries from the previous tables, Sandusky, 

 Ohio, 1917. 



Summary 



Stage. 



Number 

 of indi- 

 viduals. 



Days of duration of stage. 



from Table 

 No.— 



Average. 



Maxi- 

 mum. 



Mini- 

 mum. 



XV 





165 



70 



4.39 

 20.62 



14.78 



8 

 37 



32 



3 



XVI 





14 



XXI 





1,254 



6 



XXI 











39.79 



77 



23 









The life cycle as here presented is seen to average 39.79 days with 

 77 days as the total of the maximums and 23 days as the total of the 

 minimums. To the average of 39.79 should be added the period 

 between moth emergence and oviposition, which is usually 3 days, 

 thus making the total life cycle 42.79 days. 



SECOND GENERATION. 



INCUBATION PERIOD OF SECOND-BROOD EGGS. 



One record only was secured concerning the incubation period of 

 second-brood eggs, and that late in the season when the temperature 

 was comparatively low. Twenty-two eggs were deposited on Sep- 

 tember 1, the black spot was evident on September 9, and the eggs 

 hatched September 11, 10 days after oviposition. 

 7678°— 20 3 



