10 BULLETIN 438, U. S. DEPARTMENT OF AGRICULTURE. 
THE EGG. 
In California, in Santa Clara County, in 1912, eggs were first ob- 
served on trees as early as March 23, and in Contra Costa County, in 
1913, as early as March 25. During the last few days of March in: 
both these years oviposition was observed. In Washington, in 1915, 
numerous females were observed in the Zimmerman orchard on April 
7, though none had been found 3 days before. None was seen to ovi- 
posit on this date, and they were evidently all very recently emerged. 
A week later the period of oviposition was at its height and by April 
24 most of the adults had disappeared. The adults prefer to ovi- 
posit on those varieties of pears which leaf out early and generally 
select for oviposition a young leaf not yet unrolled. In California 
the earliest adults generally find the Bartlett not far enough advanced, 
and so the earliest eggs are deposited on other varieties. Ovipositing 
females kept in a jar were provided with cherry and plum leaves, but 
they refused these as hosts, although, in similar confinement, they 
oviposited regularly in pear leaves. 
Table II indicates the incubation period in California for 85 eggs: 
Tasie I1.—Jncubation record of eggs of the pear leaf-worm, Walnut Creek, Cal., 1918. 
Number | Date of 
of eggs de-| deposi- 
posited. tion, 
Date of | Number | Tneuba- 
hatching.) batched. |tion stage. 
Days 
118 | Mar. 29| Apr. 7 
Pls 6 10 
Apr. 9 21 11 
Apr. 10 28 12 
Apr. 11 5 13 
For this experiment 20 adults were confined in a cage in which a 
erowing pear limb was inclosed. The average incubation stage was 
11.1 days. Out of 118 eggs deposited, 85, or 72 per cent, hatched. 
Table III indicates the incubation period, in Washington, of 23 eggs 
deposited by a single unfertilized female on a pear twig kept in water. 
Tasue I11.—Incubation record of eggs of the pear leaf-worm, Wenatchee, Wash., 1915. 
Number 
of eggs ate ar Date of | Number 
depos- eposl- | hatehing.| hatched. 
‘ted tion. 
47 | Apr.11-14 | Apr. 19 10 
Apr. 20 4 
Apr. 21 1 
Apr. 22 1 : 
Apr. 23 6 
