372 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 7 



When caterpillars of this species prepare to pupate they cast their 

 skins with the heads attached and these exuviae are usually found with 

 the pupae suspended in silk spun prior to transforming. As the pupa 

 and exuvia lie in close proximity to one another it is quite easy to 

 distinguish the larval stage of the molted skin. 



The results secured from larvae reared in confinement were checked 

 b}^ observations in the field. Localities were selected with reference 

 to their elevation, infestation, and food abundance. 



At "V^ellesley, Mass., where the foliage was completely stripped, 

 a careful inspection was made. Over fifty masses of pupae were ex- 

 amined and while the percentage of female pupae was small, a suffi- 

 cient number was secured to verify the tray results. Fifteen sixth 

 stage molted skins were attached to as many female pupae, while 35 

 fifth stage caterpillars had transformed to male pupae. 



A larval collection was also made at this location. Eighty-two 

 caterpillars all of which were in the prepupal stage were collected and 

 brought to the laboratory. The stage of these was then determined 

 and the fifth and sixth stage larvae placed in separate trays in the 

 insectary. Of the 56 fifth stage larvae placed in one tray, 6 died of 

 parasitism, 4 of disease, and the remaining 46 produced male pupae. 

 There were 26 sixth stage larvae in the other tray, 3 died of parasitism, 

 and the rest developed females. Although supplied with food the 

 larvae ate but little and all excepting those killed by parasites pupated 

 within 48 hours. 



At Salem, N. H., in a lightly infested area of mixed growth the 

 results were practically the same. A few sixth stage molted skins 

 were found attached to female pupae and an equal number of fifth 

 stage molted skins were closely intermingled with masses of male 

 pupae. 



The last inspection was made at Allenstown, N. H. This infesta- 

 tion was of medium severity and located on a comparatively high ele- 

 vation. As before several masses of pupae were examined; the results 

 of which were as follows: one mass contained 10 males and 6 female 

 pupae; one 14 males and 7 females, and another 8 males and 5 females. 

 One-half mile from this point an inspection was made in a clear stand 

 of pine lying adjacent to a mixed growth. Here several masses of 

 pupae were examined and the results confirmed the former observations. 



It is not the purpose of this paper to dispute the conclusions reached 

 by former investigators of this subject, nor do we claim that the gipsy 

 moth larvae do not sometimes pass through a seventh stage. We have 

 never found it in our tray work and moreover the development of male 

 and female pupae from fifth and sixth stage larvae has been constant 

 in all our experiments. There can be no doubt but that the gipsy 



