288 MR. A. D. MICHAEL ON THE LIFE-HISTORIES 



it appeared in 1778. lu 1841 Gervais published a very short 

 description and very imperfect drawing of a species which he 

 called Olyciphagus curso)\ In 1867 Eobin and Fumose pub- 

 lished a very carefully prepared article in Eobin's 'Journal de 

 TAnatomie et de la Physiologic,' in which they, probably correctly, 

 identified de Geer's and Gervais's species ; but, for some reason 

 which is not quite apparent, they retained Gervais's name, not 

 de Geer's. M. Megnin, in the observations mentioned below as 

 having been made by him, has followed Robin and Fumose in 

 calling the species G. cursor : unfortunately neither of these able 

 authors gives a figure of their Gr. cursor ; had Eobin and Fumose 

 added such a drawing as they furnish of G. spinipes no doubt 

 could arise as to what their species is. A good figure of what is 

 apparently the male of G. domesticus is given by Berlese (Acari 

 Ital. fasc. xiv. no. 3) ; it is accompanied by a short description, 

 which, however, is supplemented by the notes to the same work 

 (fasc. i. pp. 9, 10). This author, however, does not say whether 

 he considers it to be identical with G. cursor, and the points 

 which he gives for identifying his species do not admit of com- 

 parison with those given by Eobin and Fumose for G. cursor. I 

 imagine the two species to be identical. Under these circum- 

 stances I have thought it best to give a figure of the female of 

 the species I have been dealing with, to facilitate identification ; 

 it is, I think, the G. domesticus of de Geer and Berlese, and, so 

 far as I can judge at present, it is also the G. cursor of the other 

 authors above named. 



It would be out of place here to give any formal description of 

 such well-known creatures ; but as these two species, G. spinipes 

 and G. domesticus, are commonly found together, and are not 

 easily distinguished at first, although a little practice enables the 

 student to do so with facility and certainty, it may be useful to 

 state some of the principal characters by which they may be dis- 

 tinguished ; these are : — Firstly, that the tarsi of G. spinipes are 

 thickly clothed with very fine short hairs (PI. XVI. fig. 12), but do 

 not bear any hairs much longer than the general average ; the tarsi 

 of G. domesticus are smooth, but liave a few straight hairs or 

 spines much longer than those of G. spinipes (fig. 5). The hairs 

 on the tarsi of G. spinipes are best seen in dry specimens using 

 an amplification of from 150 to 200 diameters ; they are not so 

 easily seen with lower powers nor in specimens mounted in bal- 

 sam, or even in fluid. Secondly, the tarsi of G. domesticus are 



