AJSr INTERNAL PARASITE OF THYSANOPTERA. 



33 



LENGTH OF PUPAL STAGE. 



The pupal stage of tliis liymcnopteron requires over one-half of 

 the time of the total life cycle. During the months of July, August, 

 and September, this stage is from 16 to 28 days, l)ut in the majority 

 of cases from 17 to 20 days are required. The diagram, figure 6, 

 has been prepared from the records of 146 individuals, and indicates 

 the length of tliis stage and tlie number of individuals for each 

 different lengtli. 



EFFECT OF COLD ON PUPAL STAGE. 



In order to test the effect of cokl, \mpsei brought into Washington 

 in September were exposed to outsiile conditions for over a month. 

 During this time the pupae remained dormant. About the middle 

 of October these were divided into two lots, one of 

 which was exposed while the other was placed in 

 the greenliouse. After a number of days the adults 

 began to emerge from the pupae in the greenhouse, 

 in which location the temperature was above the 

 prevailing temperature on the outside, wlule the 

 lot wliich had been placed on the outside remained 

 dormant. 



On October 19 Mr. Graf placed a number of pupae 

 of this species in cold storage at a temperature of 

 31° F. in both dry and moist atmospheres. On 

 November 28 he removed some of these pupae and 

 shipped them to the writer in Wasliington, D. C. 

 On Deceml)er 4 these were divided into two lots, 

 one of. which was placed in the outdoor insectary 

 while the other was placed in the insectary green- 

 house. The temperature maintained in this green- 

 house is moderately low and so did not tend greatly 

 to hasten development in the pupae. However, on February 14 and 

 17, adults emerged 79 and 82 days after the pupae were removed from 

 cold storage, in which they had been kept for 41 days. During the 

 three weeks previous to emergence of the adults the average mean 

 temperature in the greenhouse was 65.5° F. February 20 the pupae 

 in the outdoor insectary were still unchanged. 



THE ADULT PARASITE. 

 EMERGENCE. 



The emergence of the adult parasite is best described by Mr. Graf's 

 notes as taken at the time of observation, Ausust 9, 191 1 . 



Several adult parasites were emerging from the pupal cases and were carefully 

 watched. In every case noted, the anterior end of the pupal case, covering the face 



Fig. 5. — Thripoctenus 

 Tusselli: Pupa, ventral 

 view. Greatly en- 

 larged. (Original.) 



