178 THYSANOPTBRA AND ORTHOPTERA. 



on the Thysanoptera and Orthoptera, laying emphasis upon the former. 

 One of the least known and one of the best "known groups of insects thus 

 became the centers of attention. The data secured on these orders is 

 thought to be of sufficient interest to warrant publication, to the ex- 

 clusion of the scattering information obtained on other groups. 



I wish to express my appreciation of the assistance and interest, in 

 all my work, of the Chief Field Naturalist, Dr. A. G. Ruthven. Ac- 

 knowledgments are made to the other persons to whom I have become 

 indebted in the progress of the work, in the introductions to the dis- 

 cussion of the groups. 



THYSANOPTERA. 

 INTRODUCTION. 



In a list of literature dealing with Thysanoptera, which is fairly com- 

 plete up to the time of its publication, Hinds (1902, pp. 221-231) in- 

 cludes 480 titles. The earlier papers were nearly all of a systematic 

 nature, as are also many of the more recent ones. Many of the refer- 

 ences are to textbooks or other compilations, and do not represent 

 original work.- A considerable number were issued from experiment 

 stations or were published in agricultural periodicals, and were naturally 

 concerned chiefl\' with the economic importance of the group, — the 

 dangers of epidemics of thrips and the means of combating them. A 

 few were written primarily as contril^utions to anatomy. Others were 

 published l)y economic botanists interested particularly in the relation 

 of thrips to plants. 



When the ])apers falling into one or another of the above categories 

 are deducted, the number which treat of the l^iological aspect is so 

 small as to plainly indicate the need of work from the standpoint of the 

 biologist. It is not intended to decry the publications mentioned, for 

 many of them contain necessary and valuable contributions; I merely 

 call attention to the paucity of biological investigations represented by 

 them. It is true that some of the experiment station workers have 

 studied the life histories of indi\i duals; and they and others have ac- 

 cumulated a certain amount of data on habits, but any one acquainted 

 with the present state of knowledge of the order Thysanoptera must 

 feel that there are large gaps Avaiting to be filled. 



This report is intended as a small beginning toward the obliteration 

 of the vacant spots. While some systematic work was done, the new 

 results of which were published in an earlier paper (Shull, 1909), the 

 biological aspect was made the principal subject of investigation. 

 Much work that was highly desiralile could not l)e undertaken, owing 

 to the limitations of field work. Perhaps the most crying need now is 



