54 ' Proceedings of the Biological Society of Washington. 



places the suborder Polystigmata Bagnall as a synonym of the 

 suborder Tubulifera Haliday, stating that in his opinion the 

 seven extra abdominal "stigmata' ' ascribed to that group are not 

 spiracles at all, — a statement which he reiterated in a letter to 

 the writer shortly before his death , in the following words : " It 

 seems to me that the seven extra ' stigmata ' are not real spirac- 

 ular openings (see p. 35 of my named paper). For this reason 

 I have preferred to keep the Urothripida? as a family instead of 

 adopting the new suborder. It may be that I am mistaken, 

 but I have been in a position to examine several specimens" 

 (Trybom, 1913). Trybom's paper was followed by one by 

 Dr. H. Karny (1913), in which the Polystigmata are recognized 

 as a valid suborder and the two additional families Megathripidse 

 and Hystricothripidae proposed. In February, 1914, a twelfth 

 family, the Merothripidae, was proposed by the writer for the 

 reception of an anomalous American genus. The next paper 

 which touches on the general classification of the order was 

 published by Mr. Bagnall in March, 1914, and in it the sub- 

 order Terebrantia is divided into two tribes, the ^olothripides 

 and the Thripides. Finally a thirteenth family, the Pygothri- 

 pidse was erected by the writer for a remarkable Australian form 

 (Hood, 1915). 



In the classification proposed below, most of the groups just 

 mentioned have tentatively been accepted by the writer. It 

 seems, however, that the accurate separation of a natural group 

 of organisms, its exact definition, the correct interpretation of 

 its affinities, and its assignment to a true place in the phyloge- 

 netic scheme, are impossible until the knowledge of the larger 

 group to which it belongs, and of which it forms an integral 

 part, has become really comprehensive. When finally distin- 

 guished, it will be found that the broader groups will be 

 separated by fundamental characters of ancient origin, while 

 the less comprehensive groups will be distinguished by characters 

 of less importance, produced in comparatively recent times. 

 Thus, while we look to color, sculpture, size, and other trivial 

 differences for the separation of species, we expect the defini- 

 tion of larger groups to call into service important differences 

 in the main body itself. The separation of families on sexual 

 characters, on minor antennal differences observed in solitary 

 specimens, and on the relative length of the tenth abdominal 



