60 CALIFORNIA ACADEMY OF SCIENCES. 



That change by which the one-time subgenera of Phil- 

 opterus are now put on equality with the genus Tricho- 

 dectcs, and similarly the subgenera of Liotheum on equal- 

 ity with Gyropus, seems to me ill-advised. The two 

 genera found on mammals differ so radically and in so 

 many ways from their related genera in each family that 

 I believe their striking host and structural differences 

 should be emphasized in the classification. I propose, 

 therefore, in the light of the present position of the Mal- 

 lophaga as an independent order of insects, to rank the 

 Nitzschian families as suborders, and the Nitzschian gen- 

 era as families, and the Nitzschian subgenera, the genera 

 of present day writers, as genera. This will leave un- 

 changed the present generic names and ranking, but will 

 restore the expression, first indicated by Nitzsch in his 

 generic rankings, of differences between the mammalian 

 parasites and the avian parasites. This re-ranking, which 

 is practically a return to classification of Nitzsch, finds 

 expression in the keys and synopses which I have ar- 

 ranged to receive all of the genera so far recognized. 



Although the Mallophaga include already nearly iooo 

 described species there are but few genera and these 

 genera are difficult to separate. In other words, the 

 whole group is a series of closely related and intergrad- 

 inof forms. The causes and conditions of this state of 

 affairs I have already attempted to explain in the para- 

 graphs under the head of " Distribution" (antea). In 

 this place the facts of this close inter-relation come home 

 to us in the attempt to arrange keys for the separation of 

 the genera. I found trouble, when beginning the study 

 of the Mallophaga, in distinguishing by the published 

 keys certain genera; whether a Philopterid parasite was 

 a Docophorus or a Nirmus, or whether a Liotheid para- 

 site was a Mcnopon or a Colpocephalum, were questions 



