DAMiEUS GENICQLATUS. 429 



Acarus geniculahis, Schrank. Fauna boic, vol. iii, p. 208, 



No. 2666. 

 Belba geniculata, Gervais, Hist. Nat. des Insectes Apteres, 



Walckenaer, t. iii, p. 256. 



— — Can. e. Fan., p. 33. 



— — Berlese. Acarofauna Sicula, la ser., p. 10. 

 Oribata — Latreille. Genera Crustaceorum et Insectorum, 



t. i, p. 149. 



— — — Hist. Nat. des Crust, et des Insect., 



t. vii, p. 400. 

 Tique noir et lisse des pierres (?), GeolFroy. Insect, des environs 



de Paris, t. ii, p. 626. 

 DamcBus geniculatus, Koch. Heft 3, fig. 13. 



— — Nic. P. 460, pi. viii, fig. 1. 



— torvus, Koch. Heft 3, fig. 14. Nymph (?). 



Average length about 1*45 mm. 



Average breadth about 1 '00 ram. 



Average length of legs (first pair) about 1'50 mm. 



Average length of legs (second pair) about 1'20 mm. 



Average length of legs (third pair) about 1-35 mm. 



Average length of legs (fourth pair) about 1*75 mm. 



Very great confusion has arisen over the synonomy 

 of this species. It has been confused with D. clavipes 

 by all the earlier and some later writers, and in many 

 instances with other species also. It may be taken 

 that Linnaeus , Fabricius, Schrank, Latreille, and G-ervais, 

 did not distinguish between geniculatus and clavipes, 

 and probably other allied species were included. 

 Linnaeus's description is clearly not sufficient for 

 identification. It is ^^ Acarus niger,femoriim geniculis 

 subglobosis ; habitat in arborum ramis emortuis." 

 Fabricius simply copies Linnaeus. Latreille and 

 Geoffrey identify the latter's " Tique noir et lisse des 

 pierres^' with Linngeus's A. geniculatus, otherwise the 

 identity might well be doubted. Latreille and subse- 

 quent writers copying him also identify the Linnsean 

 species with Notaspis clavipes of Hermann, but that 

 author, although his descriptions are imperfect, had a 

 knack of drawing his creatures so as to be very 

 characteristic, and his species is certainly not the one 

 now usually known as geniculatus, and which probably 

 was the Linnsean species. Another serious element of 



