Table I . — Feeding period of third 

 larval stage of A. chalybea, North 

 East, Pa., 1916. 



8 BULLETIN 901, U. S. DEPARTMENT OF AGRICULTURE. 



1 by 4 inch vials. Transformations from the prepupal and pupal 

 stages to the adult were passed in vials of the same size partially 

 filled with earth. To determine the duration of each of these periods 

 in the ground two methods were employed, as follows: 



The first was to place a vial five-eighths of an inch in diameter 

 inside of a vial 1 inch in diameter, filling the space between the two 

 with earth. In this narrow space mature larvae were placed and 

 most of them were forced to form their pupal cells next to the glass 

 surface, where their transformations could be observed readily. The 

 outer vial was covered with black paper, which was removed only 

 when observations were being made. For convenience of identifica- 

 tion each cell was marked with a wax pencil. This method was 

 faulty, because of the difficulty of maintaining the normal soil mois- 

 ture in so thin a layer. 



It was later learned that by pressing the earth in the middle of the 

 vial, leaving the earth at the sides comparatively loose, about half of 



the larvae would form pupal cells along 

 the sides of the glass. It was necessary, 

 of course, for success with this method, 

 as with the former, that the vials be 

 wrapped with black paper. This method 

 was most used in 1917. 



These methods of observing trans- 

 formation in the ground were developed 

 in the latter part of 1916 and the data 

 on these transformations secured during 

 that season are very meager. Hence 

 records for the prepupal, pupal, and 

 callow adult stages of both species are 

 given only for 1917. 

 Detailed life-history studies of the typical grapevine flea-beetle 

 did not begin in 1916 until the majority of the larvae were at least 

 half grown, since they were undertaken for comparison with the more 

 common "small form." Accordingly rearing records cited below 

 begin with the third larval stage in 1916. 



DURATION OF FEEDING PERIOD OF THIRD STAGE IN 1916. 



The duration of the feeding period of the third larval stage varied 

 from 6 to 13 days, with an average of 7.75 days, as shown in Table I. 

 The period covered by these records extended from June 12 to July 8. 



DURATION OF PERIOD IN GROUND. 



Number 



Duration 



of larvse. 



of period. 





Bays. 



18 



6 



29 



7 



17 



8 



15 



9 



6 



10 



2 



11 



2 



13 



'89 



2 7.75 



1 Total. 



2 Weighted average. 



The duration of the period in the ground of 87 individuals 

 reared varied from 15 to 24 days, with an average of 20.71 days. 



