LIFE-HISTORIES OF GAMASIN^. 301 



and named Acarus coleoptratorum*, which is found abundantly 

 parasitic upon Coleoptera, Hymenoptera, &c, and especially on 

 the common Geotrupes stercorarius . The leading character of 

 the species, or so-called species, is, that the dorsal surface is not 

 covered by one chitinous plate, but by two separate ones, leaving 

 a soft white space between them and round the hinder plate. 

 (This is shown in Plate XXII. fig. 2.) 



Greoffroyf followed Linnaeus, calling the creature "mite des 

 coleopteres ;" and De GeerJ also preserved it, calling it " Acarus 

 fucorum." Schrank§, Hermann ||, Frisch^f, and others of the 

 earlier writers also treat it as a well-established species. It was, 

 however, Latreille ** who instituted the genus Gamasus ; and he 

 made coleoptratorum the type of a new genus, Carpais, which 

 genus he abandoned ff in his later works. The creature, from 

 its abundance, came to be considered as a type of the G-amasinae, 

 which type has been followed by numerous writers down to 

 the present time. Dr. Kramer in 1876 £ % points out that more 

 than one species has been included in the name " Gamasus 

 coleoptratorum'" he defines them, and makes the separation of 

 the two dorsal plates a ground for dividing the genus Gamasus 

 into subgenera. 



Other writers, such as Koch §§, have made the presence of a 

 space between the two dorsal plates, or the visibility of the line 

 of juncture, a means of classification. 



Kramer's paper appeared in the first number of the 'Archiv fiir 

 JNaturgeschichte ' for 1876; in May of the same year appeared 

 Megnin's paper above cited (in Eobin's ' Journal de l'Anatomie ' 

 &c). Megnin utterly denies that coleoptratorum is a species at all. 

 He says that the division of the plates on the back simply shows 

 that the creature is in an immature stage, and is a nymph, or, 

 rather, is constituted of the nymphs of at least three species, of 



* Syst. Nat. 13th ed. p. 1026. no. 27. 



t Hist. Ins. torn. ii. p. 623. no. 4. 



J 'Mem. pour servir a l'hist. des Insectes' (Stockholm, 1778), tome vii. 



112. 



§ ' Obs. Hist. Nat.' tab. i. fig. 13. 



|| • Memoire apterologique ' (Strasbourg, 1804), p. 74. 



% Ins. torn. iv. tab. 10. 



** ' Precis des Oar. gen. des Ins.' 1796. 



tt Magas. Encyclop., Gamasus, &c. J| Loc. cit. p. 75. 



§§ • Uebersicht des Arachnidensystems,' 3tes Heft (Nurnberg, 1842). 



