ACAHINA PIGNOGONIDA. 



495 



Deg., Argas rej/tejcus, Latr., on Pigeons, occasionally on Man. A. 

 Fisch. Notorious for its bite. 



Fam. Gamasidae. Beetle-mites. Chclicerre chelate. Pedipalpi five-jointed. 

 The legs end with two claws and a sucker. Tracheae are present. Some of 

 them lead a free life and are predacious, some are parasitic on Beetles and on 

 the skin of Birds and Mammals. Gnmasvs coleoptratorvan L., Derinanyssvs 

 avhtm. Dug.. Pteroptvs vcspertilionis Herm. 



Fam. Hydrachnidae. Water-mites. Body globular, often brightly-coloured. 

 Chelicerje usually with a claw-like terminal joint. They have swimming legs, 

 and two or four simple eyes. There are trachere. The larva;, when hatched, 

 adhere with their large suctor'al cone to aquatic Insects, on the blood of which 

 they live. Hydrachna cruenta, 0. Fr. Mull. Ata.r lionzi Clap., in the mantle 

 cavity of the Uninn. Limnoeltares holiwriceits Latr. 



Fam. Trombidiidae (fig. 388). Body brightly coloured and covered with 

 hairs ; the pedipalpua has a claw and a lobe-like appendage. Eyes present. 

 Respiration by tracheae. The hexapodous young live as parasites on Imecta 



FIG. 389. Pygnogonum littonile, 

 (regne animal) AB, pair of legs 

 used for carrying the eggs. 



FIG. 388. Tromtjidium holuteri- 

 ceum (after Mognin). 



and Arachnida, sometimes on Mammalia, and on Man, in whom they (as Ltptux 

 autumnalli) produce a transitory affection of the skin. Trombidium holose- 

 riceitm L. Erythr&u* par let inns Hcrm. Tetranychvs t clearing L. Spinning 

 mite. 



Fam. Oribatidse. Chclicerre retractile .and chelate. Pedipalpus five-jointed, 

 with toothed biting plate on its basal joint. Ocelli absent. Orilates alatutt 

 Herm., under moss. 



Fam. Bdellidae. The cephalic region is elongated to form a proboscis, and 

 is distinct from the rest of the body. The chelicera; are chelate. The pedipalpi 

 are long and thin. The animals creep about on damp ground. liiJclln lonrji- 

 cornis L. 



PYGNOGONIDA.* 



Milne Edwards and Kroyer placed the Pygnogonida among the 

 Crustacea ; latterly, however, they have been generally placed between 



* A. Dohrn, " Die Pantopoden des Golfes von Neapcl und der angrenzenden 

 Mcercsabschnitte," Eine Monographic, Leipzig, 1881. 



