794 PAEASITIC DISEASES. 



sheep's head, will serve to convince them that they are in error. 

 Without dwelling upon this point, we have further to observe 

 that the perfected bots usually pass from the nostrils to the 

 ground by the same way that they entered, and thence-forward, 

 having penetrated the soil, they accomplish their subsequent 

 metamorphosis in a manner very similar to that of their con- 

 geners. The pupal state is acquired in about two days, but 

 they remain concealed in the soil for a period of six or eight 

 weeks. At the expiration of this period the lid of the cocoon 

 is raised, and the insect prisoner makes its escape in the usual 

 manner. 



In perusing the above remarks, it will be noticed that, if Mr. 

 Eiley's statements are to be accepted as correct, the gadfly of 

 the sheep reproduces viviparously. This is a point of consider- 

 able interest, since, so far as we are aware, all the other gadflies 

 bring forth their young in the egg condition. According to 

 Verrill, who quotes from the First Annual Report on the Noxious 

 Insects of Missouri (given in the Connecticut publication already 

 cited) for 1868, Mr, Kiley states that Mr. Cockrill had removed 

 upwards of three hundred living larvae from the body of a single 

 gadfly. Soon after the flies have effected their escape from the 

 cocoon, they set about operations for the continuance of the 

 species ; and as they are neither furnished with a mouth nor 

 other means of taking in nourishment, it is obvious that the 

 pleasures they enjoy during the winged state must be exceed- 

 ingly short-lived. 



TEACIIEAPJA. 



As with the dipterous insects, so with the members of this 

 large order or division of arachnidans. Whilst many species 

 are externally parasitic, only a very small number can in any 

 true sense be called entozoa. One species, however, of the 

 present group is not only internally parasitic in the larval state, 

 but also in the full-grown or sexually mature condition ; conse- 

 quently it has even more right to be regarded as an entozoon 

 than any of the gadflies. The parasite in question is the Pen- 

 tastoma tcenioides. In the adult state, this worm occupies the 

 nasal and frontal sinuses of the dog, sheep, and horse ; and in one 

 of its larval stages it is found either encysted or free in the viscera 



