186 THYSANOPTERA AND ORTHOPTERA. 



often found quite exposed on grass blades; or when found in concealed 

 situations, it was usually among the young blades that were not yet 

 unrolled (e. g., on sea sand-reed, Ammophila arenaria), and here the 

 location may have been determined by the greater tenderness of the 

 young leaves. Owing to the comparative scarcity of Aptinothrips 

 rujus on blue grass (Poa pratensis), and to its sluggishness, I have no 

 direct observations upon the degree of concealment of this species. But 

 judging from the ease with which it could be swept from the grass with 

 a net, I am inclined to place it among the superficial species, as shown 

 in the classified list above. An examination of the habitat of Anapho- 

 thrips striatus (see p. 210) shows that it was captured in a large majority 

 of cases from grasses: and Aptinothrips rufus with its variety connati- 

 cornis was swept or sifted only from grass collections that were largel}^, 

 or exclusively made up of blue grass {Poa pratensis). It would appear 

 from these observations that the local distribution of these two species 

 of thrips is determined chiefly by the character of the food; while the 

 fact that the adults of Anaphothrips striatus were more abundant on 

 rolled leaves of wild rye {Elymus canadensis) than on flat ones would 

 indicate that protection is a minor factor in distribution, — unless, in- 

 deed, it should be found that some of those which had been on exposed 

 surfaces were washed ofT by rain, or captured by enemies, factors which 

 have nothing to do with the distribution of the thrips in the first place. 



Another species may be considered, namely, Anthothrips verhasci. 

 Although hundreds of specimens were collected, not a single specimen 

 was taken from any other plant than the common mullein {Verbascum 

 ihapsus). I have found as many as 874 specimens of this species, young 

 and adults together, on a single spike of mullein about 17 cm. long. 

 There seems no doubt that this species desires protection, for when 

 disturbed both young and adults crawled away among the mullein 

 buds or seed capsules. However, when the spike was crowded, a num- 

 ber of adults could often be found on the under side of leaves and on 

 the stem, some of them more than 30 cm. below the spike. 1 have also 

 transplanted these thrips from a spike of mullein to the leaves of a 

 plant in its first year, which had no spike. Specimens thus transplanted 

 were thriving two weeks after the change, at which time observations 

 ceased. Here, apparently, is a species that seeks protection, but en- 

 dures exposure rather than quit its food plant. 



It is unnecessary to go into detail regarding each species. Using 

 such data as has been employed in the case of the five species mentioned, 

 namel}^, Euthrips tritici, Thrips tabaci, Anaphothrips striatus, Aptino- 

 thrips rufus, and Anthothrips verbasci, I have grouped all the species 

 taken according to the factor which I believe plays the chief role in 

 determining their habitat. The arrangement follows: 



