THE PEACH AND PLUM SLUG. 



93 



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observations seem to indicate that the females normally infest the 

 lower branches first, gradually going higher and higher as the destruc- 

 tion of the lower leaves progresses. 



On September 15 occurred a very hard shower, accompanied by 

 a high wind, that destroyed a large percentage of the larvae that were 

 on the trees at the time. This constituted another setback from 

 which the species had hardly recovered when cold weather set in. 



On October 5 practically all of the accessible foliage of the trees in 

 the yard was examined and no stage of the sawfly found, except 8 

 esfgs. These were all located on one 

 leaf and had apparently all been para- 

 sitized. 



In the earlier attempts at life- 

 history work great difficulty was ex- 

 perienced on account of the delicacy 

 of the young larvae and the large 

 death rate among them when trans- 

 fer by hand from one leaf to another 

 was attempted. In addition to this, 

 it was found impossible to follow a 

 given lot of larvae through to maturity 

 if left on the tree, because of their 

 habit of moving over considerable 

 areas and their consequent loss. The 

 attempts to curb this tendency re- 

 sulted only in the death of the larvae. 

 Also, the adults refused to oviposit 

 under any form of restraint. For 

 these reasons a special method of pro- 

 cedure was adopted and a special 

 rearing cage designed. Many unin- 

 fested terminal clusters of leaves were 

 marked with blank string tags . These 

 clusters were examined dailv, and 

 when eggs were found on any of the leaves the infested leaves were 

 marked by clipping the tips and a lot number was placed on the tag, 

 the number corresponding to a card on which notes were recorded. 

 The leaf cluster was then allowed to remain on the tree until just 

 before or just after the hatching of the eggs, when the whole cluster 

 was cut off with a long stem and transferred to the rearing cage. 

 This cage (fig. 23) consisted of a tumbler of sand, into the center 

 of which was thrust a vial and at the side a tube open at both 

 ends. The stem was placed in water in the vial and held upright by 

 a perforated cork. The tube reached well toward the bottom of 

 the tumbler, and was for the purpose of watering the sand without 



Fig. 23. — Cage used in rearing the peach and 

 plum slug: a, Tumbler; b, sand for pupation 

 of the insects; c, tube, open at both ends, for 

 moistening sand from bottom; d, vial of 

 water for keeping food fresh; e, lantern 

 chimney; /, cheesecloth cover; g, rubber 

 band. Reduced. (Original.) 



