No. 567] BIOLOGY OF THE THYSANOPTERA 165 



habitat and behavior could be made. One fact, however, 

 is of interest in connection with an experiment to be de- 

 scribed. While the adults live mostly on flowers, some- 

 times concealed, sometimes more or less exposed, the 

 larvae were always found concealed; moreover, it was 

 with difficulty that the larvce could be driven from their 

 retreat by pressing the flowers. Frequently such vigor- 

 ous squeezing was necessary to dislodge them that the 

 larvae emerging were injured ; and a flower so treated was 

 often found later to contain numerous dead larvae. In 

 this respect, the behavior of this species is in considerable 

 contrast to that, for example, of Euthrips tritici. 



The habitats and behavior described above can be "ex- 

 plained" in large measure if we say, as I at first proposed 

 (1911), that certain species seek protection, or that cer- 

 tain other species have specific food requirements. Thus, 

 it might be said that Euthrips tritici seeks safety in 

 crevices, and flees danger when disturbed ; that Anapho- 

 thrips striatus "prefers" grass for food, that it requires 

 as much protection as its commissarial activities permit, 

 and that its habitat and behavior are such as best fulfill 

 these requirements. Anthothrips verbasci might be said 

 to be limited to one article of diet, while protection is a 

 minor matter. 



This explanation might be acceptable as far as it goes, 

 were it not that no species is immune to attack. I have 

 seen larvae of Anthothrips verbasci frequently captured 

 by various bugs. Heads of mullein where thrips are 

 found nearly always bear bugs of the family Capsidae, 

 and observations convince me that they prey almost 

 wholly on the larvae of the mullein thrips. The degree to 

 which they check the thrips was tested experimentally as 

 follows : Two mullein spikes of approximately equal size 

 and equally infected with thrips were selected. The 

 predatory bugs were removed from one of them, after 

 which the spike was enclosed in a thin muslin bag. Two 

 weeks later the bag was removed. The enclosed spike 

 bore a large number of full-grown larvae, a few had 



