148 ARACHNIDA. 



scopic observations by Messieurs Raspail, Galet, and other 

 French and German writers. 



The Gamasus Coleoptratorum and Uropoda vegetans are 

 two small species, often found in immense numbers upon 

 various ground beetles, the latter being attached to the insect 

 by means of a very long and slender filament arising from 

 the extremity of its body. . Mr. R. Patterson of Belfast has 

 communicated to me a species of Steropus madidus, so com- 

 pletely enveloped in these minute creatures as to render it 

 impossible to perceive the least portion of its body. 



The species of insects of which the genus Ixodes are com- 

 posed are named ticks, and are of small size ; the body is 

 swollen and leathery ; the head is small, and fm-nished with 

 a powerful rostrum, composed of two retroserrated plates, 

 which the insect inserts into the flesh of dogs and other ani- 

 mals, upon which it is parasitic, and upon whose blood it 

 subsists. In the West Indies they attack the horse and ass 

 in such quantities, that it is the usual practice to have these 

 animals fetched up from grass once a~week to be " ticked." 

 They especially attach themselves at the base of the ear, 

 and, if neglected, will sometimes become so numerous that 

 the animal loses all power of raising its ears at will. Their 

 powers of reproduction are so great that the animals infested 

 sometimes sink under their attacks. 



The tj^ical species is the Ixodes ridnus {Acarus ricinus 

 Linn.), which is parasitic on the dog. It is serviceable to 

 anoint the infested parts with oil or soft soap. The species: 

 of this genus require a more minute revision than has yet 

 been given to them. 



ORDER V. PODOSOMATA (Lcach). 



This order, as above characterized, is of small extent, and 

 comprises two families — 



1. PycnogorddcB J 2. Nymphonidce. 



