ACARINA. 131 



to comb the fibres of the web, just as we comb our 

 hair with a common comb. 



The spinnerets, with which spiders form their web, 

 are very curious organs. They are situated at the 

 under and hind part of the body, and consist of two 

 or three cones, or papillae, on each side. On the 

 summits of these papillae are very numerous bristle- 

 like tubes, through which the secretion of certain 

 glands passes ; this secretion, when hardened by ex- 

 posure to the air, forms the fibres of the web. 



On carefully examining a spider's web, the radial 

 fibres, or those which pass from the centre to the cir- 

 cumference, will be found to be smooth, these fibres 

 serve to fix the web ; while the cross fibres are covered 

 with numerous viscid globules, which serve to attach 

 flies or other prey to them. This difference of the 

 fibres is best observed with a hand-lens. 



ACARINA, or the Order of Mites. Here belongs 

 cheese-mite, Ac? arm domes' ticus (PL IX. fig. 36) . Its 

 body is somewhat milky white, oval, and furnished 

 with feathery hairs. When viewed from beneath, 

 there is seen a transverse line, indicating the separa- 

 tion of the thorax from the abdomen ; and another 

 line in front of this, with four minute tubercles, from 

 each of which arises a hair. The head is pointed and 

 beak-like, forming a ros'trum (rostrum, a beak), con- 

 sisting of two mandibles pressed together ; these can 

 only be seen to be separate when dissected apart with 

 the mounted needles. Each mandible is chelate 

 (jCflW) forceps), or has the form of a lobster's claw ; 

 and beneath the two mandibles is a flat membranous 

 under lip or labium, consolidated on each side with a 

 palp. The legs are four pairs, as in all the Arachnida ; 

 they are pinkish, 6-jointed, and terminated by a leaf- 

 like sucker and a minute claw. 



The males (fig. 38) are smaller than the females, 

 the fore legs being much stouter, and furnished with 

 a blunt tooth (fig. 38 a). The eggs can often be dis- 



