96 



DECIDUOUS ERUIT IXSECTS AXD INSECTICIDES. 



THE EGG. 



The egg is transparent white, ovoid, slightly more than one-half 

 a millimeter in its longest diameter, with one side slightly more 

 rounded than the other as in the egg of the pear slug. In eggs in 

 which incubation has continued for some time the developing larva 

 can be easily distinguished. 



The incubation period of 74 eggs was determined (see Table I) ? 

 and it varied from 4 to 6 days, with an average of 4.9 days. 



Table I. — Incubation period of the peach and plum slug, Tallulah, La., 1910. 



Lot No. 



Date of 



oviposi- 



tion. 



Date of 



Number Ineuba- 

 of indi- tion 

 natcnmg. viduals# period . 



13 1 Apr. 14 



17 Apr. 13 



110 Aug. 10 



111. 

 112. 

 113. 



114. 



Aug. 11 



...do 



Aug. 12 



...do 



115 ! Aug. 14 



116 .- I... do 



Apr. 18 



...do 



Aug. 14 

 Aug. 16 



...do 



...do 



Aug. 17 

 Aug. 16 

 Aug. 17 

 Aug. 19 



...do 



117 j Aug. 21 Aug. 27 



Total and average ; 



1 

 1 

 6 

 3 

 3 

 1 

 2 

 1 

 1 

 22 

 29 

 4 



Days. 



4.0 

 5.0 

 4.0 

 5.0 

 5.0 

 4.0 

 5.0 

 4.0 

 5.0 

 5.0 

 5.0 

 6.0 



4.9 



THE LARVA. 



As is the case with the pear slug, the larva in escaping from the egg 

 cuts a crescent-shaped slit in the wall of its cell. When first hatched 

 (fig. 24, b) it is creamy white with the head slightly darker and the 

 eyes and mouth parts brown, and lacks the slimy covering. It has, 

 in addition to the 6 true legs, 7 pairs of prolegs. It begins to feed 

 almost immediately, becoming quickly coated with the secretion, 

 and within half an hour a line of green appears down its whole length, 

 due to the food in the alimentary canal. 



The first damage by the larva consists hi very small pinholes eaten 

 into the leaf from the underside, all of the tissue being removed except 

 the upper epidermis. As the larva grows and its jaws become 

 stronger the size of the eaten patches increases until they become 

 large blotches. The upper epidermis is, however, never eaten. 



The larva grows rapidly (see fig. 24, c), molting four times during 

 its growth. The first instar is from less than 2 to 4 days in duration, 

 averaging about 2 days. The second and third histars are of nearly 

 like duration, and the fourth about 3 days in length, the total feeding 

 period being about 9 or 10 days in duration in warm weather. Two 

 individuals were recorded in which the feeding period lasted for 22 

 days, but these were from a lot which was under observation during 



