GAMASIDS. 1G3 



CASE ralists, De Geer, Latreille, &c., thought that this was something 

 of the nature of an umbiUcal cord, by which the mite drew 

 nourishment from the beetle, or from others of its own species, 

 on which it might be fixed, for they are sometimes found in 

 clusters, one piled above the other. Others imagined that it wa. 



^ a silken cord by which the parasite attached itself so that the 



beetle could not get rid of them by brushing them off. The latter 

 may be the purpose of it, but it is neither an umbilical tube nor 

 a silken cord. Examination of the cord shows that it- is not silk, 

 and not a tube, neither can it be used in any way for conveying 

 nourishment, for the mite can, at will, detach itself from the beetle. 

 De Geer knew this, but supposed it was the end of the cord next 

 the beetle that became detached. He says that they are able to 

 remove when they please by crawling in a certain direction until 

 the iJOrd is sufficiently strained to cause the end to be detached 

 from the beetle. This is a mistake :. it is the end of the cord next 

 the mite that becomes detached. Duges ascertained its real 

 nature. He says that he has found the Uropoda free under 

 stones in bad weather as well as fixed to burrowing beetles. The 

 pedicle or cord he describes as a homy filament, stiff, elastic when 

 dry, soft, becoming flexible in water without dissolving ; and in it 

 there is to be found neither cavity, nor fibres, nor any organic 

 structure. Fixed firmly on the coat of the beetle by a sort of 

 spreading base, it is attached to the mite at the other end by a 

 similar base, which exactly covers the anus of the mite, which, as 

 in the other Gamasidse, is situated on the under side, a short dis- 

 tance within the posterior margin of the body ; and hence he con- 

 cluded that it is not a silken matter spun by special organs, but 

 the viscous and dried excrements of the animal, and of which it 

 can get rid whenever it makes a new excretion. 



Duges knew only one species, but we have two or three from 

 beetles in different parts of the world which differ in the propor- 

 tions of the buckler or back, some being more rounded or more 

 oval than others. In other respects they all look very much alike, 



L 2 



