THYSANOPTERA AND ORTHOPTERA. 203 



Similar counts made with reference to the direction of the sun are 

 recorded in Table VII. 



TABLE VII. — Showing the number of individuals of Anthothrips verhasci taken 

 on the sunny and shady sides of spikes of mullein {Verbascum thopsus) at 

 times not closely following a rain. 



No of "spike '^^' °^ ^hrips on sunny side. Xo. of thrips on shady side. 



"^ ' Young. Adult. Young. Adult. 



1 13 6 11 8 



2 28 1 32 1 



3 2 2 3 4 



4 138 11 109 8 



Total 181 20 155 21 



Some irregularities were of course introduced into the above counts 

 because it was a matter of judgment to determine whether the rows of 

 buds examined on opposite sides of a spike were equal. The work was 

 done carefully, however, with this source of error constantly in mind. 

 It is thought, therefore, that if there was any marked tendency of the 

 thrips to congregate on a definite side of the spike, it would be notice- 

 able in the counts. In Table \1, there is a larger number of thrips on 

 the windward side in every case, but the difference is too small to in- 

 dicate any preference for that side. In Table VII, the total shows a 

 small majority of thrips on the sunny side; but in two of the individual 

 cases the majority were on the shady side, and in another case the two 

 numbers were ecjual. Defects and differences in the plant tissues on 

 different sides could not readily be measured, and were not taken into 

 account. 



I conclude from these data that in dry Aveather thrips distribute 

 themselves uniformly over symmetrical spikes. During rains, how- 

 ever, or shortly after them, it appears from Table "\^ that there is a 

 tendency to favor a definite side of the spike, namely, the one protected. 

 In onl}' two cases out of the eleven was the number of thrips greater 

 on the windward than on the leeward side ; in one of these (No. 8) the 

 number was quite small; in the other (No. 3) the observations were not 

 made until 3 hours after rain had ceased, and the spikes were practi- 

 cally dry already. The total of the eleven counts shows a decided 

 majority of thrips on the leeward side, in the ratio of 1.28 to 1. If 

 Nos. 3 and 4 be rejected as belonging more properly to dry weather 

 counts, the number on the leeward side bears to that on the windward 



