THYSANOPTERA AND ORTHOPTERA. 201 



in the webs of small spiders on rolled leaves of wild rje (Elymus cana- 

 densis). In several instances mites were found attached to thrips, as 

 is well known, usually near the base of the abdomen but in one case at 

 the articulation of the hind femur and tibia. The most common insect 

 enemy which I have noted is a small l)lack bug {Triphleps insidiosus) 

 mentioned by Osborn (1888), found in flowers, on some grasses, in ter- 

 minal bunches of leaves, in fact almost anywhere where thrips may be 

 found. It was quite common on the blades and among the silks and 

 husks of common field corn {Zea mays), and its presence was so closely 

 associated with the presence of thrips that I used it as a means of find- 

 ing the latter. Thrips lived quite commonly concealed at the bases of 

 the blades of corn, but not nearlj- on all, nor even on a large proportion 

 of the leaves. On those leaves where Triphleps insidiosus was found, 

 there were usually thrips. The bug would go about with its long beak 

 thrust forward and when it came upon a thrips, it would crawl up to 

 the latter, pierce it near the middle of the body, and bear it away im- 

 paled on its beak. Rove-beetles (Staphylinidae) were often found in 

 flowers with thrips, but as this family is not generally predaceous, they 

 may not attack thrips. Certain members of the Staphylinidae live 

 symbiotically with ants, but the advantages derived from the ants can 

 hardly also be derived from thrips. 



It seems quite probable that such insectivorous lairds as the ruby- 

 throated humming-bird {Trochilus coluhris), which visits flowers, would 

 devour thrips. The stomach of one individual which was captured in 

 August was examined for these insects, but the only contents besides 

 some plant hairs and pollen grains were legs of small spiders together 

 with irregular chitinous pieces which were probably portions of the 

 bodies of the same animals. This single stomach-examination, does 

 not, however, even make it probable that thrips are not sometimes 

 captured by humming-birds. 



Rains. This seems to be the great enemy of thrips. ■ It has been 

 noticed mam^ times that these insects are less abundant in wet seasons 

 than in moderately dry ones. During the summer it seemed to me that 

 thrips were not as common immediately after a rain as they were be- 

 fore, but as hard rains were uncommon in Huron County during the 

 season, I hav^ no definite data on this point. I have, however, at- 

 tempted to determine experimentally the relations of thrips to water, 

 and to observe the effect of rain in their natm^al habitat. It was noticed 

 that, on the spikes of mullein {Verbasciini thapsus), during or after a 

 rain, specimens of Anthothrips verhasci were not as abundant on the 

 side which the rain struck as on the protected side. Definite counts 

 were made in a number of instances. A row of buds, flowers or seed 

 capsules, was gently examined one at a time, and the thrips on or be- 

 tween them were counted. Usually a row two buds wide through the 



