374 PREDACIOUS AND PARASITIC 



pennate hairs, not identified, are actually aphis destroyers ; while 

 I have no doubt that several other closely-related species, which 

 I have been unable to determine, probably have the same habit. 

 But it should be observed that the total destruction of aphides 

 thus effected is comparatively small, and that in all probability 

 the injury inflicted on vegetation far outweighs the service render, 

 ed to man by these minute creatures. 



The habit of these mites is to spin a slight fine web on the 

 under surface of the leaves of the vegetation which they haunt, 

 and under this protection the plant-feeders draw their nourishment 

 from the host, while the carnivorous mites go out to find food, and 

 both dispose, between the filaments of the web, the eggs which 

 are to continue the species. These eggs are shown on Plate XVII., 

 Fig. 8. The most striking feature of the mature mites is the 

 curious capitate, or plumose, bristles with which they are closely 

 covered. So densely are they placed, that in T. holosericeum a fine 

 velvety appearance is produced, resembling a close, short fur. The 

 plumose bristles which cover some of the most determined aphis- 

 eaters, seem to consist of several short, tapering joints, from each 

 of which some fine hairs diverge obliquely. The character of the 

 slender double claws and the capitate hairs, and brush-like pads, 

 which are their general appurtenances throughout the family, are 

 of great interest ; and the small, brilliant, circular eyes may be 

 observed among the bristles along the front of the mite and im 

 mediately above the opening of the mouth. The chelicer^e do 

 not terminate in nippers, and the colour, which is usually of a 

 more or less brilliant red, is sometimes spotted with dark brown. 



The position of the Family Trombidiidcc, in the Class Arach- 

 NiDA, may be seen by the following tabulation : — 



Class Arachnida. 

 Orders. — Arfhrogastra, Arancida, Acarma, Tardigrada, Lin- 

 guatulina, Paiitopoda. 



The Acarina are divided into seven families, distinguished 

 as follows : — 

 I. — Forepart of head prolonged into a distinct beak 

 and separated by a constriction from the rest of 

 the body ... ... ... ... Bdellidcz 



