DIRECT INJURIES CAUSED BY INSECTS. 89 



oviposits a in them, and so occasions very dangerous 

 ulcers. It would be an Acarus, he observes, but it has 

 only six legs. Now Hermann affirms, that some species 

 of Trombidium (a genus separated by Fabricius from 

 Acarus) have in no state more than six legs 5 . Others of 

 the tribe of Acarina, and the insect in question amongst 

 the rest, may be similarly circumstanced ; or those that 

 Rolander examined might have been larvae, which in this 

 tribe are usually hexapods. 



Linne appears to have been of opinion that many con- 

 tagious diseases are caused by mites c . How far he was 

 justified in this opinion I shall not here inquire; facts 

 alone can decide the question, and observations made by 

 men acquainted with Entomology as well as the science 

 of diseases. Considerable deference and attention, how- 

 ever, are certainly due to the sentiments of so great a 

 naturalist, in whom these necessary qualifications were 

 united in no common degree. With respect to the dys- 

 entery and the itch, he affirms that this had been mani- 

 fested to his eyes. You will wish probably to know the 

 arguments that may be adduced in confirmation of this 

 opinion ; I will therefore endeavour to satisfy you as well 

 as I am able. The following history given by Linne seems 

 to prove the dysentery connected with these animals. 



Rolander, a student in Entomology, while he resided 

 in the house of the illustrious Swede, was attacked by the 



a It is to be hoped this new word may be admitted, as the laying 

 of 'eggs cannot otherwise be expressed without a periphrasis. For 

 the same reason its substantive Oviposition will be employed. 



b Mem. Apterologique, 19. 



Insecta ejusmodi minutissima, forte Acaros diversae speciei causas 

 esse diversorum morborum contagiosorum, ab analogia et experientia 

 hactenus acquisita, facili crcdimus negotio. Aviocn, Ac. v. 94, 



