60 Psyche [April 



ing from the groups of pupse found, even more may complete their 

 development in a single host. This is impossible with the smaller 

 hosts of T. russelli. The larvae are always oriented in the same 

 direction, their heads towards that of the thrips. The skin of the 

 latter soon splits and shrivels to a small pad, to which the larvae 

 remain attached until they pupate. As in the case of russelli the 

 contents of the alimentary canal are retained until after the insect 

 has completed its transformation. This substance, bright crim- 

 son at first, loses its color shortly before the pupal stage, and is 

 voided by the adult as a milky fluid. 



In a few cases the length of the pupal stage was determined. 

 Five larvae developed from two thrips (three in one, and two in 

 the other) began to darken on August 31. The first three were 

 completely black by next day, the other two twenty-four hours 

 later. On the 11th of September four of the five pupae (all of the 

 first lot and one of the other) hatched. Two were males and two 

 females. The last pupa, a female, hatched on the 13th. 



Adult: Perhaps the most striking difference between nuhi- 

 pennis and the Western species consists in the presence of males in 

 the former. Thripoctenus russelli was found to be both partheno- 

 genetic and thelytokous, no males being produced through all the 

 generations that were reared. In nubipennis the male is not un- 

 common, though slightly rarer than the female. Copulation was 

 observed on more than one occasion. It is a process of very brief 

 duration. 



The sex of the offspring of unfertilized females could not be 

 determined, owing to the aforementioned difficulty in keeping the 

 thrips alive. 



The adults ran about actively but were not observed to fly, and 

 seldom jumped. They did not feed when offered syrup, but the 

 females were fairly well supplied with the juices of the thrips. 

 Those that oviposited frequently survived the others, but four or 

 five days was about the maximum length of life under laboratory 

 conditions. 



The presence of a member of this genus in the Eastern States is 

 probably of no economic importance, since the thrips upon which 

 it preys are not injurious. They belong to a different suborder 

 from the hosts of the two species of Thripoctenus hitherto de- 

 scribed. Whether or not nubipennis would attack members of 



