[12] Read at the meeting of the National Academy of Sciences, April 20, 1888.
J. Ritsema, in Petites Nouvelles Entomologiques for September 15, 1869, described the species as Platypsyllus castoris. He found it on some American beavers (Castor canadensis) in the zoological garden of Rotterdam. He considered it to "undoubtedly" belong to the Suctoria of De Geer, and to form a new genus of Pulicidæ.
In the same year, in the Tijdschrift voor Entomologie, 2d ser., vol. v., p. 185 (which I have not seen), the same author publishes what is apparently a redescription of the insect. He gives his views more fully as to its systematic position, considering that it belongs to the Aphaniptera, and is equivalent to the Pulicidæ.
In the same year, Prof. J. O. Westwood (having previously read a description of the species, November 9, 1868, before the Ashmolean Society of Oxford) published in the Entomologist's Monthly Magazine, vol. vi., October, 1869, pp. 118-119, a full characterization of the insect under the name of Platypsyllus castorinus. A new order, Achreioptera, is established upon the species, which he very aptly likens, in general appearance, to a cross between a flattened flea and a diminutive cockroach. "The abnormal economy of the insect, its remarkable structure, the apparent want of mandibles, our ignorance of its transformations, and the possibility that the creature may be homomorphous in the larva and pupa states," are the reasons assigned for establishing the new order, and here Prof. Westwood is perfectly consistent, as in his famous "Introduction to the Classification of Insects" the Forficulidæ are placed in the order Euplexoptera; the Thripidæ in the order Thysanoptera; the Phryganeidæ in the order Thrichoptera; the Stylopidæ in the order Strepsiptera; and the Pulicidæ in the order Aphaniptera.
In 1872, Dr. J. L. Le Conte published his paper "On Platypsyllidæ, a New Family of Coleoptera" (Proc. Zool. Soc. of London for 1872, pp. 779-804, pl. lxviii.), in which he shows that Platypsylla is undoubtedly coleopterous and cannot 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 Hydrophilidæ and Leptinidæ. 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, Prof. Westwood, in the "Thesaurus Entomologicus Oxoniensis" (Oxford, 1874), p. 194, pl. 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 reasons.
In 1880, P. Megnin, in "Les Parasites et les maladies parasitaires," etc., Paris, 1880, gives (pp. 66-67) a description of the family "Platypsyllines" without expressing an opinion concerning the systematic position. He also describes and figures the species.
In 1882, Dr. Geo. H. Horn (Trans. Amer. Ent. Soc., x., 1882-83; Monthly Proc., Feb. 10, 1882, p. ii.) exhibited drawings illustrating the anatomy of Platypsylla and Leptinus, and showed that a close relationship exists between these genera. Later, in his "Notes on Some Little Known Genera and Species of Coleoptera" (Trans. Amer. Ent. Soc., x., 1882-83, pp. 113-126, pl. 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 separates from Leptinus, and demonstrates their close relationship with Platypsyllus.
In 1883, Le Conte and Horn, in their "Classification of the Coleoptera of North America" (Washington, Smithsonian Institution, 1883), give (pp. 13-15) a full description of the family characters, a little modified from Le Conte's first description, but sustaining his views on the systematic position of Platypsyllidæ.