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. 



Fig. 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. 



