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sect under the name of Plafypsyllus castorimis. A new order, Achrei- 

 optera, is established upon the species, which he very aptly likens, in 

 general appearance, to a cross between a flattened flea and a dimin- 

 utive cockroach. " The abnormal economy of the insect, its remarkable 

 structure, the apparent want of mandibles, our ignorance of its trans- 

 formations, and the possibility that the creature may be homomor- 

 phous in the larva and pupa states," are the reasons assigned for estab- 

 lishing the new order, and here Professor Westwood is perfectly con- 

 sistent, as in his famous " Introduction to the Classification of Insects" 

 the ForficulidiE are placed in the order Euplexoptera ; the Thripidae iu 

 the order Thysanoptera ; the Phryganeidfe in the order Thrichoptera; 

 the Stylopidoe in the order Strepsiptera ; and thePulicidae in the order 

 Ai)hauiptera. 



In 1872, Dr. J. L. Le Conte published his paper " On Platypsyllidce, a 

 New Family of Coleoptera" (Proc. Zool. Soc. of Loudon for 1872, pp. 

 779-804, PI. LXVIII), in which he shows that Platypsylla is undoubtedly 

 Coleopterous, and can not possibly be referred to the Aphaniptera- 

 Careful descriptions and figures of anatomical details are given, and he 

 finds that its affinities are very composite, but in the direction of the 

 Adephagous and Clavicorn series. Its most convenient place is shown 

 to be between the Hydrophilidcv and Leptinidce. There seems to be no 

 good reason why the name Platypsyllus is here changed to Platypsylla, 

 a spelling adopted by most subsequent American writers. 



In 1874, Professor Westwood, in the "Thesaurus Entomologicus Ox- 

 oniensis" (Oxford, 1874), p. 194, PI. XXXVII, gives figures with details; 

 reprints his previous diagnosis, and maintains his previous course in 

 erecting a new order for the insect without giving any additional rea- 

 sons. 



In laSO, P. Megnin, in " Les Parasites et les maladies parasitaires," 

 etc., Paris, 1880, gives (pp. 66-67) a description of the family "Platyp- 

 syllines " without expressing an opinion concerning the systematic posi- 

 tion. He also describes and figures the species. 



In 1882, Dr. George H. Horn (Trans. Amer. Ent. Soc, X, 1882-'83 ; 

 Monthly Proc, February 10, 1882, p. ii) exhibited drawings illustrating 

 the anatomy of Platypsylla and Leptinus^ and showed that a close rela- 

 tionship exists between these genera. Later, in his " Notes on Some 

 Little Known Genera ad Species of Coleoptera" (Trans. Amer. Ent. 

 Soc, X, 1882-'83, pp. 113-126, PI. V, 114-116), he reviews the characters, 

 and explains and illustrates the anatomical details. The differences he 

 points out between his observations and those of Le Conte are more 

 particularly in the mandibles. In connection with this paper he also 

 describes and illustrates the structure of Leptinillus, which he sep- 

 arates from Leptinus, and demonstrates their close relationship with 

 Platypsyllus. 



In 1883, Le Conte and Horn, in their •' Classification of the Coleop- 

 tera of Xorth America" (Washington, Smithsonian Institution, 1883), 



