26 
BTLLETIX 19, U. S. DEPARTMENT OF A<tEICI7LTl t EE. 
Table X. — Transformation to adults of second-brood grape Uqfhoppen 
Date of 
examina- 
tion. 
Number 
of adults 
trans- 
formed. 
Date of 
examina- 
tion. 
1 umber 
of adults 
trans- 
form ■ 
1912. 
Sept. ' 
Sept. - 
Sept. 9 
Sept. 10 
Sept. 11 
Sepr. 12 
Sept. 13 
1 
4 

37 
76 
51 
51 
1912. 
Sept. 14 
Sept. 15 
Sept. 17 
Sept. 19 
Sept. 20 
Sept. 21 
Sept. 24 
So 
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 NTMPHAL 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 manifested 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 nvmph was observed and 
