372 PREDACIOUS AND PARASITIC 



species, and although the researches of naturalists have gone far 

 to clear away the exaggerated conceptions which formerly prevailed 

 as to the destructive properties of the Arachnida, there can be no 

 doubt that to the largest insects, and possibly to some of the 

 smaller mammalia, the bite of some species may prove fatal, while 

 the annoyance which some of the most minute species is able to 

 inflict upon men, is exemplified in the irritation following the bite 

 of the ' Harvest Bug,' one of the family Tro?nbidiidce, or ' Spinning 

 Mites,' to which the aphis-sucking species also belongs. 



This family, which belongs to the order Acarina, differs from 

 the typical Arachnid in wanting the division into head and abdo- 

 men, which is so marked a feature of the latter. In the Trom- 

 bidmm the parts answering to the head, thorax, and abdomen are 

 united to form an irregularly-shaped oblong or ovoid mass, covered 

 in the mature state with dense, short hairs or bristles of even 

 length, and sometimes knobbed at the terminations, as in holoscri- 

 ceum, or pinnate, as in some other species. 



The family comprises a considerable number of species and is 

 very widely distributed, and so nearly do many of the species 

 resemble the species of the nearly related Hydrachnidce, that 

 figures of these may be readily mistaken for those of TroitibidiidcE. 

 The Troinbidiuni in its earlier stage ( = larva), is an active six- 

 legged mite, more or less hirsute, but generally only to the extent 

 of stiff bristles, rather sparsely scattered over the body and legs. 

 The mature Trombidium is possessed of eight limbs, and has 

 generally lost the ovoid form which characterises many species in 

 the earlier stage. Four eyes are observable on the anterior surface 

 of the body in Ho/osericeum, and in other species they may with 

 some difficulty be made out, but not often very readily. 



The chelicerte are armed with two minute, needle-like appen- 

 dages, or with a pair of delicate claws, usually much thinner than 

 the claws of the legs, and they bear also at the extremity a knob- 

 like bristle, or a brush-hke appendage, the precise purpose of 

 which it is difficult to recognise. The chelicerse of the most nearly 

 allied families of the Acarina are provided with opposing claws or 

 nippers, recalling those of the crab. 



The palpi are terminated by, a horny point and a thumb-like 

 process, which is attached below the point by a delicate hinge, 



