AN INTKKNAL PAEAtilTE OF THYSANOPIEIIA. 31 



BEHAVIOR OF PARASITIZED THRIPS. 



The larvae of tlirii)s that have been parasitized require a few more 

 (lays for development before chan<^ng to the prepuj)al stage than 

 healthy individuals. It has also been noticed that j^arasitized larvae 

 are more apt to change to prepupae under the paper in the bottom of 

 the vials, wliile normal larvae generally crawl up into the edge of the 

 cotton plug before })upating. After parasitism becomes evident 

 in the ])repupal stage the doomed insects still have the power of 

 locomotion and will crawl around to some extent. But soon the 

 contents of the limbs are drawn from them and as these collapse 

 all motion in the host thrips ceases. 



TIME BETWEEN FIRST INDICATION OF PARASITISM AND FORMA- 

 TION OF PARASITE PUPiE UNDER LABORATORY CONDITIONS. 



After parasitism becomes evident in the thrips prepupae, the 

 parasitic larvie grow very rapidly and mthin two days, in a few 

 cases, have changed to pupae of Thripoctenvs 

 russelli; but the majority change in three and 

 four days. In a few cases this period has taken 

 as long as ten days, but this is unusual and 

 apparently due to some condition unknown at 

 this time. The diagram, figure 4, has been fig. s.-Parasitized prepup* 

 prepared to show the time between the ap- "^ neiioihrips fascmtus, 



^ . . IIP • P lateral and dorsal views. 



pearance or parasitism and the formation or Greatly enlarged. (Origi- 

 the parasite pupae. "'^' ) 



In a total of 223 specimens, 104, or nearly 50 per cent, changed 

 to pupie in three days, and 85, or over 38 per cent, in four days. 



EFFECT OF COLD ON PARASITIZED PREPUP^. 



A few experiments were made with parasitized prepupae of the 

 host thrips to determine tlie effect of cold on the paT'asitic larvae 

 within. On October 19 several parasitized prepupae were placed in 

 cold storage in a dry atmosphere kept at a constant temperature of 

 31° F. This material was removed November 27, 1911, and when 

 examined on December 2, by Mr. Graf, all of the parasitic larvae 

 were found to have emerged and changed to pupae. 



THE PUPA OF THE PARASITE. 

 FORMATrON. 



As has been already stated, this parasite invariably completes its 

 growth in the j)]-epupa of its host, and for tliis reason it changes to 

 the pupal stage in the localities which may have been chosen by its 



