THE PEAR LEAF-WORM. 11 
Another lot, deposited from April 8 to 11, began hatching April 18. 
The incubation period was thus 8 to perhaps 12 or 13 days. The 
twig above cited was badly wilted by the 24th, after only 50 per cent 
of the eggs had hatched, and none hatched after this date. It is 
probable that under normal conditions hatching would have been 
more regular, and also thatthe average incubation period would have 
been lengthened. It was observed that unfertilized eggs hatched as 
readily as fertilized ones. he life-history phase of parthenogenesis 
is considered farther on in this chapter in the discussion of the adult. 
THE LARVA. 
In the field at Walnut Creek, in 1913, the first larva was observed 
on Aprili1. It was about 3 days old. Two days later about 1 per 
cent of the eggs already laid had hatched. At Red Bluff, Tehama 
County, Cal., in 1911, most of the larvee were half grown on April 9, 
and in 1912 full-grown larve were found at Red Bluff April 22, and 
on May 12 no more larve could be found.t’ At Suisun and Courtland, 
Cal., in 1912, the first larvee went to the ground about April 10, but 
at San Jose not before May 1. In 1913, at Walnut Creek, the first 
larvee went to the ground about April 20, and after May 10 very few 
larvee remained on the trees. It appears that in the interior valleys, ~ 
where the pear trees move earlier, the sawflies emerge and the larvee 
mature earlier than in the coastal districts. This is doubtless due to 
climatological influences. 
The first molt is cast from 3 to 8 days after hatching, the second 
molt from 2 to 7 days after the first, the third molt from 2 to 7 days 
after the second, and from 4 to 10 days elapse between the date of 
the third molt and maturity of the larva, the variations being chiefly 
due to temperature influences. The pupal molt does not take place 
until the following spring or shortly before the issuance of the adult. 
Table IV indicates the larval life observed at San Jose, Cal., in 1912. 
TaBLE L[V.—Larval stages of the pear leaf-worm, San Jose, Cal., 1912. 
Date lar-| Active Date lar-| Active 
Date egg | —, Date egg | ~ 
INI) || Fase va spun larval No. atahaa | vVaspun | larval 
hatched. | cocoon, life. hatched. eoeaual life, 
Days. Days 
VW) Apr.) 7 |) May) ¢ 32 10 | Apr. 12) May 1 
2 Gowesee May 10 33 11 | Apr. 13 | May 12 29 
3 Gow May 12 35 Ze aC Ou May 14 31 
4 | Apr. 8 | May 11 33 13 Gowns ig CO 31 
5 do solo en t 33 14 Gowan May 16 33 
6 || Apr. 9 |) May 9 30 15 (clo Nee May 18 35 
7 | Apr. 10 |) May 17 37 16 | Apr. 17 | May 13 26 
8 | Apr. 12] May 10 28 17 | May 2) May 31 29 
9 Clo aih May 11 29 
1 Letter from Mr. C. B. Weeks, Tehama County horticultural commissioner. 
