SYSTEMATIC RELATIONS OF PLATYPSYLLUS, AS 

 DETERMINED BY THE LARVA. 



By C. V. RlI,EY. 



There is always a great deal of interest attacMng to organisms 

 which are unique in character and which systematists find difficulty 

 in placing in any of their schemes of classification. A number of 

 instances will occur to every working naturalist, and I need only 

 refer to Limulus, and the extensive literature devoted during the 

 past decade to the discussion of its true position, as a marked and 

 well-known illustration. In Hexapods the common earwig and flea 

 are familiar illustrations. These osculant or aberrant forms occur 

 most among parasitic groups, as the Stylopidae, Hippoboscidse, 

 Pulicidae, Mallophaga, etc. Probably no Hexapod, however, has 

 more interested entomologists than Platypsyllus castoris Ritsema, a 

 parasite of the beaver. 



During a stay at West Point, Nebr., in October, 1886, I learned 

 from one of my agents, Mr. Lawrence Bruner, that there was a 

 beaver in a creek not far from that point, and I at once made 

 arrangements for him to trap the beaver, and to look particularly for 

 living specimens of Platypsyllus on the skin, and especially the 

 earlier stages. He succeeded in capturing the beaver and sent me 

 some fifteen specimens of the larva and also some imagos, but 

 neither eggs nor pupae were found. A glance at the larva satisfied 

 me at once of its coleopterous nature ; but as we have, waiting to be 

 worked up and published, an embarras de richesses entomologiques in 

 the collections of the National Museum, and as circumstances 

 largely decide the precedence, I should probably not have called 

 the attention to this larva for some time, had it not been that at the 

 last monthly meeting of the Entomological Society of Washington, 

 Dr. Horn, who was present, announced the finding, the present 

 spring, by one of his correspondents, of this very larva, and exhib- 



