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THE AMERICAN NATURALIST [Vol. XL VIII 



place where they can best suck the juices of the plant, but 

 there is no need to assume that they deliberately choose 

 this location in order to get their food most easily. Both 

 adults and larvae rest on these leaves with their heads 

 directed toward the base of the leaf, and crawl toward 

 the base of the leaf if disturbed, not because protection is 

 most quickly to be found among the curled leaves at the 

 center of the plant, but because the thrips are positively 

 geotropic. 



Anthothrips verbasci. — The larvae of this species live 

 hidden among the flowers of the mullein spike, not be- 

 cause they must get their food there, for they can get it 

 from any part of the plant; nor do they hide there, it 

 seems to me, to secure protection. They remain in these 

 crevices because, excepting the largest larvae, they are 

 positively stereotropic and negatively phototropic. The 

 adults are sometimes exposed, sometimes concealed, prob- 

 ably because in the former case they are usually indiffer- 

 ent to light, in the latter case negatively phototropic. (Or 

 may they be made negative or indifferent according as 

 they live — for one reason or another — concealed or ex- 

 posed?) 



Thus, while Anthothrips verbasci is limited to one food 

 plant, and the food requirements are therefore probably 

 exceedingly important, yet the distribution and behavior 

 of the insects on this plant may be explained without ap- 

 pealing to anything like " choice" in other matters. 



Eegarding Anthothrips niger, I wish to call attention 

 to but one fact. The difficulty with which the larvae are 

 driven forth from a flower in which they live appears to 

 be due, not to a persistent attempt at concealment, but to 

 the fact that on being disturbed they are temporarily 

 negatively phototropic; if the disturbance is continued, 

 the negative response continues. 



The only argument which, it appears to me, could be 

 advanced in favor of assuming that the Thysanoptera 

 choose their locations, instead of adopting simple re- 

 sponse to external stimuli as the correct explanation of 



