AN INTKHNAL PAHASI'I'K OF Til YSANOPTKIiA. 



51 



MEANS OF COLONIZING THE PARASITE. 



Experiments conducted during 1911 between Compton, Cal., and 

 Washington, D. C, have shown that this parasite can be distributed 

 in two ways. Eitlier the material can be collected in the field and 

 shipped direct to the point where its introduction is desired, or the 

 material can be placed in cold storage and thus kept until a more 

 favorable period. 



In shij)ping material direct from the field two methods liave been 

 used that give good results. Of these the more promising is to 

 collect material where the parasitism is high and put the thrips 

 larvic in vials as described under "Methods of collecting for evidence 

 of parasitism" (p. 28). Then, as soon as the parasitic larvae have 



Fig. 11.— Mailing tubes used in shipment of thrips parasites. Original. 



transformed to pupae, they should be packed carefully in cotton, to 

 prevent jarring, and shipped. (See fig. 11.) In the other method 

 the only diiT(u-eiice is that the material is shipped as soon as placed 

 in the vials. While this has the advantage of giving more time for 

 shipping, it unfortunately seems to cause greater mortality in the 

 parasitized material. It is also possible to pick leaves of plants 

 infested by parasitized thrips, and pack these in cigar boxes and 

 ship direct. However, this method has not given as good results 

 during the past year as tlie other two methods. 



During the fall of 1911 much material was placed in cold storage 

 in Los Angeles. In these experiments parasitized prepupa? of the 

 thrips were placed in vials or in rubbish and then put in either the 



