296 Account of the Yiilex penetrans L. 



bad swellings and ulcers, and even death, are the conse- 

 quences of their intrusion, especially in animals in which their 

 extraction is not so easily effected. M. J. Natterer thus lost 

 his excellent hound. A multitude of these fleas had inserted 

 themselves in all the four feet, and the poor animal became 

 the sacrifice of their love of nestling. By means of these feet, 

 which were cut off, and sent in spirits to the Imperial Museum 

 at Vienna, we have been enabled to give an accurate descrip- 

 tion and figure of this remarkable insect. 



On the dog's foot (represented at Jig. 40.) the brown points a 

 are the spots where a sand flea has inserted itself. If these 

 spots be examined with a lens, a small hole is discovered in 

 their centre ; and, if it be carefully loosened around, a small 

 vesicle, or ball, will fall out of the integument, leaving behind 

 it an empty space, as represented in Jig. 40. b. These balls 

 contain the sand flea half-enclosed in a membranous vesicle. 

 By using some care, the insect can be extracted from this, 

 which then resembles a berry of the mistletoe (Fiscum album 

 L.) Fig. 40. c, represents one of these fleas magnified. It 

 is transparent, and it has, on the surface turned outwards, a 

 small aperture, surrounded by a brown circle, which is the 

 anus. On the surface turned inwards towards the skin, the 

 head and feet of the flea are seen. [Jig. 40. d.) The whole 

 ball, therefore, is nothing else than a gravid female, swollen 

 to an enormous size, which, seen in profile, appears as repre- 

 sented at fig. 41. e. If the extremely delicate membrane of 

 the abdomen be opened, a conglomeration of white, transpa- 

 rent, immovable, cylindrical eggs present themselves, which 

 are figured at Jig. 40. J. They are innumerable, and they 

 hang in a filiform cellular membrane together. The nearer 

 these eggs are to the anal aperture, the larger is their size; 

 and the nearer the centre of the whole mass, the smaller they 

 become. 



As all the sand fleas we examined had the same form, and 

 all had a more or less swollen abdomen, it would seem that 

 females only, and after impregnation, insert themselves into 

 the integument of animals, to find there a [more abundant 

 nourishment for the developement of their eggs. As, besides, 

 no larvae or maggots were found in the feet, but tolerably 

 forward eggs at the orifice of the anus, it is probable that the 

 female, like that of our common flea, lays its eggs on the 

 ground, where they then transform themselves into larva?, 

 pupae, and perfect insects.* 



* Dr. K. D. Rodschild, in his work " Medecinische," &c, 8vo, p. 307., 

 is of opinion that the sand flea lays no eggs, but that the larvae are deve- 



