-October, '14] MOSHER AND WEBBER: GIPSY MOTH LARVAL MOLTS " 369 



The larvae used in the straight and combination feeding experiments 

 were obtained from a newly infested locality at Barre, Mass. The 

 colony is situated outside the generally infested territory and the 

 larvae were in a supposedly healthy condition. 



In order that larvae might be reared under the most natural condi- 

 tions, all of the experiments were conducted in a large outdoor insect- 

 ary. 



There were about 174 trays used in the combined experiments 

 which necessitated the use of about 17,000 caterpillars. 



The eggs were hatched under natural conditions and 100 of the 

 young larvae, as nearly uniform in size as possible, were placed in trays 

 prepared for them. 



The trays used in these experiments are a modification of the Fiske 

 tray. They are of two sizes, one for the newly hatched larvae, 6" x 7" 

 x2"; and those used for the older larvae, \2\" x 121" x 2^". The 

 trays used in 1912 were wood frame with cloth bottom, but as consider- 

 able difficulty was experienced by the young larvae in crawling over the 

 cloth, a paraffined paper tray was substituted in 1913, and proved to 

 be a vast improvement over the other. This paper tray when folded 

 fitted snugly into wooden trays previously used. A band of tanglefoot 

 1 inch wide was placed on the upper inside margin of the trays to 

 prevent the larvae from escaping and the intrusion of others. 



The food was kept fresh by placing the cut end or twigs bearing 

 foliage in a receptacle filled with water. A specimen vial about 1 

 inch scjuare and 3| inches long and with the neck projecting at an 

 angle of 45° was used for this purpose. The stem of foliage selected 

 for food was thrust through a hole in a cork stopper which was inserted 

 in the vial of water. By using a vial of this description the food was 

 never in contact with sides of trays but lay evenly distributed across 

 the center, thereby preventing all opportunity for escape of larvae. 



Each tray was inspected daily and a note made of the number of 

 larvae in each stage. The dead or dying caterpillars were removed 

 and the tray cleaned of all excrement and other refuse. If at any 

 time there was an excessive number of dead larvae the living ones were 

 transferred to a fresh tray. In this way sanitary conditions were 

 maintained. A careful and complete record was also kept of the 

 amount of food consumed by the larvae and a note made of any changes 

 affecting them. 



The results of experiments in regard to sexual variation of larvae 

 confirmed those of last year and established the fact that the variation 

 is constant so far as these experiments go. Of a few thousand larvae 

 that were under observation in the later stages, 560 transformed into 

 chrysalids. Three hundred and twenty-five of these were males and 



