THE PEACH AND PLUM SLUG. 95 
the cavity thus formed the egg is placed. (See fig. 24, a.) The 
probability that this is the method of oviposition is supported by 
the fact that the adult was never observed on the underside of the 
leaf, but always on the upper side. Moreover, the pear slug, which 
is closely related to this species, performs the same operation from 
the underside of the leaf, depositing the egg just beneath the upper 
epidermis. Morgan (loc. cit.) mistook the portion of the lower 
epidermis, which forms the floor of the nidus, for a ‘“‘mucilaginous 
secretion which extends beyond the real egg and produces a much 
larger surface for attachment.”’ That this idea was erroneous can be 
easily seen by dissecting the nidus. 
Fic. 24.—Developmental stages of peach and plum slug: a, Egg in situ; b, newly hatched larva; c; 
larva nearly full grown; d, larva after last molt, ready to enter ground for pupation; e, prepupa; /, 
pupa; g, adult. All much enlarged. (Original.) 
In selecting a leaf for oviposition the female usually chooses one 
some distance back from the terminal bud but one which is still 
tender. The fresh terminal leaves and the oldest tough ones seem 
to be avoided, although rather tough leaves are preferred to the 
newest growth. 
The number of eggs in a single leaf may vary from 1 to 25. It 
seems likely that a female, after selecting a suitable leaf, may deposit 
many eggs in it. This conclusion is strengthened by the fact that 
on April 9, within 9 days of the first appearance of the adults, and 
when infested leaves were very scattered, one leaf was found which 
contained 25 eggs. 
In some leaves the location of each egg is indicated on the upper 
side by a small, reddish-purple spot. 
