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BULLETIN 19, U. S. DEPARTMENT OP AGRICULTURE. 

 Table X. — Transformation to adults of second-brood grape leafhoppers. 



Date of 

 examina- 

 tion. 



Number 

 of adults 

 trans- 

 formed. 



Date of 

 examina- 

 tion. 



> umber 

 of adults 

 trans- 

 formed. 



1912. 

 Sept, 7 

 Sept. 8 

 Sept. 9 

 Sept. 10 

 Sept. 11 

 Sept. 12 

 Sept. 13 



1 

 4 

 

 37 

 76 

 51 

 51 



1912. 

 Sept. 14 

 Sept. 15 

 Sept. 17 

 Sept. 19 

 Sept. 20 

 Sept. 21 

 Sept. 24 



85 

 63 

 16 

 26 



5 

 11 



3 



The last of the nymphs transformed to adults on September 24. 

 This rearing experiment indicates that the transformation of the 

 second-brood adults which were the progeny of the earliest nymphs 

 of the season to appear upon the vines was much too late in the season 

 for the production of a third brood of nymphs. 



REARING EXPERIMENTS TO DETERMINE LENGTH OF NYMPHAL STAGES. 



A series of rearing experiments was made to determine the length 

 of the nymphal stages. The newly hatched nymph was placed in a 

 cage made as follows: A hole about an inch in diameter was punched 

 out of the center of a piece of velvet about 2 inches square. The 

 velvet was then placed, nap side against the leaf, on the underside 

 of an uninfested leaf. A square of heavy manila paper of the same 

 size was placed on the upper side of the leaf directly above the square 

 of velvet, to hold the leaf rigid. The newly hatched nymph was 

 then placed on the underside of the leaf in the circular space cut out 

 of the square of velvet. A small watch glass, convex side up, was 

 placed over the circular hole in the velvet so as to overlap about 

 one-fourth of an inch onto the velvet. Then the watch glass, the 

 velvet, the portion of grape leaf, and the square paper were all held 

 tightly together by means of four paper clips, by slipping on one of 

 the clips from each side of the square, making them clasp the paper 

 and the velvet and overlap on to the watch glass and hold the latter 

 firmly in place so that the nymph could not escape. In some instances 

 squares of thin sheets of celluloid were used in place of the watch 

 glasses, but it was found that the small nymphs would sometimes 

 drown in the moisture collecting on the inside of the celluloid. Then, 

 too, the concave of the watch glass made the space larger. Even 

 with the watch glasses, drowning of the nymphs was likely to occur. 

 In order to prevent this, two squares of velvet were glued together 

 with the nap side out. This raised the watch glass a greater distance 

 from the leaf, giving more space between the back of the nymph 

 and the glass, and less drowning of nymphs resulted. Each cage was 

 examined daily; thus the condition of the nymph was observed and 



