262 A. D. MICHAEL ON A SPECIES OF GAMASUS. 



epistonie is quite different in the two sexes, that of the male 

 (Fig. 4) being a triangular or somewhat lancet-shaped blade, 

 nearly as broad as long ; while that of the female (Fig. 12) is a 

 long, strong, narrow spine, with two small teeth near the base, 

 and then widening ; this is more the form of the epistome in 

 Kramer's species. This seems to me to have a somewhat im- 

 portant bearing on this system of classification, as where one 

 species varies in the two sexes, it is probable that there are 

 others that do the same ; therefore, where figures of the oral 

 tube, or epistome, are given, it would probably be desirable to 

 say which sex they belong to, or whether both sexes are alike. 



The next part requiring notice is the mandible of the male. It 

 has been mentioned that these organs vary much in form, there 

 being often chitinous. appendages to the chela which assume the 

 most singular shapes. In Kramer's G. magnus the upper (fixed) 

 limb is about half as long again as the lower (movable) limb, 

 and forms an irregular cone with a blunt, rounded point. Just 

 at the first glance the mandible of the present species looks as 

 though it were an exaggeration of the same thing, as one limb 

 is longer than the other ; but it is soon seen that what exists 

 here is exactly the contrary of the arrangement in Kramer's 

 species. The fixed limb here is quite short, and has one terminal 

 bifid tooth, and one large single tooth. The movable limb is 

 immensely prolonged, being more than five times as long as the 

 fixed limb. It forms a great spear-like organ, along the distal 

 half of which in the upper median line runs a thin, sharp blade. 

 The point is extremely sharp, so that the whole structure is a 

 formidable weapon. This brings me to an interesting feature in 

 the use of this mandible. I ventured to assert some time since 

 that some species of Gamasus which I had been breeding for the 

 purpose of a previous inquiry* were strictly predatory crea- 

 tures. My reason for this was that I failed to get them to eat 

 vegetable food, but that they fed eagerly upon cheese-mites, and 

 throve excellently on that diet through several generations. 

 Some of the Italian Acarologists, however, doubted this, and main- 

 tained their previous opinion, that all the Gamasidce fed upon decay- 

 ing vegetable matter. The present species certainly is predatory in 



* " Observations on the life-histories of Gamasinae, with a view to assist 

 in more exact classification," ' Journ. Linn. Soc. Zool.,' Vol. xv. (1881), 

 p. 297. 



