204 THYSANOPTERA AND ORTHOPTERA. 



side the ratio of 1.87 tO' 1. I conclude from these figures that this 

 species (Anthothrips verhasci) is somewhat influenced by the rains. 



If, then, a thrips is in a position where it cannot well escape the water, 

 or is too sluggish to crawl away when once wet, it is interesting to know 

 what will happen. It was stated under the heading "Dissemination" 

 that when specimens of Thrips physopus were immersed in water they 

 were all dead at the end of 50 hours. To determine the maximum 

 time of immersion that could be endured, several groups of larvae of 

 Anthothrips verhasci were enclosed in draw-string muslin bags, and sunk 

 in water. Care was taken on immersion that all air bubbles should be 

 removed from the bags. At the end of various intervals a bag was 

 opened and the condition of the thrips noted. The results are shown 

 in Table VIII. 



TABLE VIII. Showing condition of larvae of Anthothrips .verhasci after immer- 

 sion in water for various periods. 



TVT f rr.- • , XT f i u " No. aUvc On Time elapsing after removine 



No. of Time m water No. of thrips ^^ ,^j ^^^^^ larvae began to crawl^ 



group. in hours. immersed. from water. . in minutes. 



First larva. Last larva. 



1 19.4 5 5 2 70 



2 28.3 5 5 40 90 



3 38.0 5 1 .90 



It appears from these figures that a rain lasting 40 hours, or keeping 

 the plants wet for that length of time, would probably be fatal to all 

 larval thrips of this species which could not escape to a protected situ- 

 ation. Passing showers, on the other hand, occurring infrequently, 

 would have little effect on them. It is probal)le, however, that even 

 brief showers, occurring at frequent intervals, would in time have a 

 detrimental effect. 



SYSTEMATIC AND DETAILED TREATMENT OF SPECIES. 



For the identification of the twenty-one species of Thysanoptera 

 which I have collected in Hm-on County, the following key has been 

 compiled. Little attempt has been made, beyond the separation into 

 suborders and families, to arrange the species taxonomically. This is 

 especially true of the Tubulifera, in which there are fewer clues to 

 relative specialization than among the Terebrantia. In the latter sub- 

 order, the arrangement of species in the key is roughly that of ascend- 

 ing specialization, as adopted by most workers on Thysanoptera. This 



