18 
BULLETIN 19, U. 8. DEPARTMENT OF AGRICULTURE. 
LENGTH OF EGG STAGE. 
Since we were unable to secure actual records of egg deposition 
from which to make a starting point in order to determine accurately 
the length of the egg stage, an approximation of this period was ob- 
tained in the following manner: 
During the season of oviposition a number of adults were confined 
hi an air-tight globe cage PL II. fig. 1) upon the uninfested foliage 
of a small grapevine possessing not more than three or four healthy 
leaves. After 24 hours all the adults were removed. The vine was 
protected from further infestation and after seven days had elapsed 
was examined daily for the appearance of nymphs. A record was 
made of the date of the first nymphs to appear. These were removed 
from the cage and all other nymphs to hatch were removed at inter- 
vals of 24 hours. In the experiments recorded below the adults were 
placed on an inclosed grapevine. July 4. at 1 p. m. These adults were 
removed July 5. at 1 p. m. The newly hatched nymphs were removed 
on the dates recorded in Table I. 
Table I. — Length of incubation period of eggs of the grape leafhopper. 
. hilts placed on vine July 4.1p.m.: adults removed 
from vine July -5. 1p.m. 
Date and hour of removal of newly 
hatched nymphs. 
Number 
of nymphs 
removed. 
Incuba- 
tion, 
period. 
July 17,. lp. m. 
July IS'. 1p.m. 
Jul v 19, 1p.m. 
Jul v 20, 1p.m. 
Jul v 21, l'p. m. 
1912. 
Dags. 
11 to 13 
12 to 14 
13 to 15 
14 to 16 
15 to 17 
50 adults placed on vine June 25. 2 p. m.: adults removed 
from vine June 26, 2 p.m. 
1912. 
.. 9, 2.30 p. m 
JuTv 10, 2.30 p.m... 
Julv 11, 2.30p.m... 
Jtdy 12,2.30p.m... 
July 13, 2.30p.m... 
Daus. 
11 to 13 
12 to 14 
13 to 15 
15 to 17 
100 adults placed on vine June 27. 2 p. m.: adults removed 
from vine June 2S. 2 p. m. 
Julv 12, 2p.m. 
July 13, 2p.m. 
July 14, 2p.m. 
Julv 15, 2p.m. 
Julv 16, 2 p. m. 
1912. 
Days. 
14 
13 to 15 
44 
14 to 16 
19 
15 to 17 
x 
11 to IS 
1 
17 to 19 
50 adults placed on vine July 27, 2 p. m.: adults removed 
from vine July 2S, 2 p. m. 
1912 
Aug. 20, 2 p. m IS 
: 21, 2p. m 
Aug. 22. 2 p. m 11 
Days. 
22 to 24 
23 to 25 
24 to 26 
•50 adults placed on vine August 10, 2 p. m.: adults removed 
from vine August 11. 2 p. m. 
LUg. 24, . • 
nig 25, 2 p. m. 
Aug. 26. 2 p. m. 
\ . 27, 2p. m. 
:- 28, 2p. m. 
Aug. 29, 2 p. m. 
Sept. 1. . 
Days. 
12 to 14 
13 to 15 
:- ■ : 
17 to 19 
2<3 to 22 
