OF THE GAMASID.E. 103 



true nature, and he describes it as a horny filament, stiff and 

 elastic when dry, and containing neither cavity, fibres, nor any 

 organic structure. Firmly fixed to the body of the beetle by a 

 sort of spreading base, and to the mite by a similar enlargement, 

 which exactly covers its anus, he considered that it was not a 

 silken cord spun by any special organs, but the viscous and dried 

 excrement of the animal, and of which it can get rid whenever it 

 makes a new excretion. The one which I kept alive was attached 

 to the upper dorsal plate of G. Coleoptiatorum when I found it on 

 the 1 6th November, and it remained in this position without any 

 sign of life until the 14th January (during which time it could 

 have taken no nourishment), when I found it had disengaged 

 itself and was walking about. 



The mandibles of this creature are very peculiar, being as long 

 as its entire body, within which they are generally retracted, their 

 base lying just above the attachment of the cord, and they appear 

 to have the power of darting out these mandibles to their full 

 length (though I have never seen them do so), the long, sharply- 

 pointed end of one of the claws — quite different to that of Gama- 

 sus — rendering it admirably fitted for use as a spear. 



The smaller Gamasids — those without any division of the 

 dorsal plate — were named by Duges Gamasiis margmatiis^ on 

 account of the white membranous margin which shows round the 

 edges of the dorsal shield, and which increases or diminishes in 

 width, according as the creatures are more or less distended with 

 food. Andrew Murray says of it : — " This species is also found 

 on beetles more frequently even than the last {Coleoptratoruni), 

 and sometimes along with them ; but, generally speaking, not more 

 than one species of mite is found on the same beetle." In this, 

 however, my experience differs from his, as I have always found it 

 less abundant than Coleoptratorum^ and invariably in their com- 

 pany, always finding two and generally three species of mite on 

 the same beetle. Hermann, in his " Memoire Apterologique," 

 reports that this species lives on dead bodies (for which reason he 

 named it Acarus cadaveri?ius), and mentions that one was found 

 running on the brain of a soldier who died in the Military Hos- 

 pital at Strasburg, whose skull had been opened but a minute 

 before. Hermann appears to have thought that the mite was 



