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PLATYPSYLLUS— EGG AND ULTIMATE LARVA— 

 Dr. Horn's Reclamation. 



BY C. V. RILEY. 



The egg and the pupa of Platypsyllus are yet unknown. I have 

 for some time endeavored to obtain them, and specimens recently 

 received as such gave hope, from the finder's account, that the lacunae 

 in the life-history of the genus might at last be filled. But examina- 

 tion dispelled the hope; yet not without adding something to our 

 knowledge of the development of this curious beaver pararsite. 

 The only reference to the egg is that contained in Dr. Horn's article 

 in the ' ' Transactions of the American Entomological Society (Vol. 

 XV, p. 25)," where it is stated that the eggs were observed, and 

 that "they are minute objects, not fastened to the hair, as is the case 

 with lice, but plastered firmly to the skin among the thickest hair." 

 This, failing in description, might apply to the egg of any other 

 minute creature, and I have, in fact, some reason for concluding 

 that the objects referred to in the observation were not the eggs of 

 Platypsyllus, but those of quite a different insect. The eggs, as 

 observed in the oviduct of the female Platypsyllus, are sufficiently 

 uncharacteristic, except as to their flattened form; they are 0.4 mm. 

 long and 0.2 mm. in broadest diameter, non-sculptured, white, 

 broadly ovoid, but much flattened on two sides. The structure in- 

 dicates that they may either be thrust under the scales of the skin or 

 fastened thereto. 



What was sent as the pupa, proves to be a most interesting 

 larval stage and in keeping with the Mallophagous appearance of 

 the beede. This larval stage might at first sight be characterized as 

 a Mallophagan by even the most careful zoologist. The larva, as 

 hitherto described and figured, even in the largest specimens, 

 whether from Dr. Horn's material or my own, has always seemed 

 to me inexplicably small as compared with the imago, and if the 

 form which I now describe is (and I can believe it nothing else) the 

 final larval form of Platypsylhcs, then the larvae hitherto described 

 had not yet gone through their final molt. A glance at the accom- 

 panying figures suffices to show the remarkable superficial resem- 

 blance to the lice in question, and only when the structure, especially 

 of the leg and mouth-parts is studied, does its Platypsyllus nature 

 appear. The description will also show how greatly it is modified 

 from the earlier larval stages already described. One is justified 

 from the facilities for grasping which it possesses, as from the posi- 

 tion of the head, in inferring this stage quiescent, and in this respect, 



