262 ■ LECTURE XIX. 



The degree and mode in Avhich spiders exercise this singular 

 secreting faculty varies considerably in the different species. Some, 

 as the Clubiones, line with silk a conical or cylindrical retreat, formed, 

 perhaps, of a coiled-up leaf, and having an outlet at both extremities, 

 from one of which may issue threads, to entrap their prey. Others, 

 as the Segestrice, fabricate a silken burrow of five or six inches in 

 length, in the cleft of an old wall. The Mygale cementaria lines a 

 subterraneous burrow with the same substance, and manufactures a 

 close-fitting trap-door of cemented earth lined with silk, and so at- 

 tached to the entry of the burrow as to fall down and cover it by 

 its own weight, and which the inmate can keep close shut by means of 

 strong attached threads. 



The arrangement of spiders by M. Walcknaer into families, cha- 

 racterised by their habits, places the principal varieties of their webs 

 in a very concise point of view. 



The Cursores, Saltatores, and Laterigradce, make no webs ; the 

 first catch their prey by swift pursuit, the second spring upon their 

 prey by insidious and agile leaps ; the third run, crab-like, sideways 

 or backwards, and occasionally throw out adhesive threads to entrap 

 their prey. The Latebricolce hide in burrows and fissures, which they 

 line with a web. The TubicolcB inclose themselves in a silken tube^ 

 strengthened externally by leaves or other foreign substances. The 

 NiditelcB weave a nest, whence issue threads to entrap their prey. 

 The FilitelcB are remarkable for the long threads of silk which they 

 spread about in the places where they prowl in quest of prey. The 

 TapitelcB spin great webs of a close texture like hammocks, and wait 

 for the insects that may be entangled therein. The Orbitelce spread 

 abroad webs of a regular and open texture, either circular or spiral, 

 and remain in the middle or on one side, in readiness to spring upon 

 an entangled insect. The RetiteltE spin webs of an open mesh-work 

 and of an irregular form, and remain in the middle or on one side to 

 seize their prey. Lastly, the Aquitelce spread their silken filaments 

 under water to entrap aquatic insects. 



The silken secretion of spiders is not applied only to the formation 

 of a warm and comfortable dwelling for themselves, or of a trap for 

 their prey : it is often employed to master the struggles of a re- 

 sisting insect, which is bound round by an^i^xtemporary filament, spun 

 for the occasion, as by a strong cord. Lastly, a softer and more 

 silken kind of web is prepared for the purpose of receiving the eggs, 

 and to serve as a nest for the young. 



All the Arachnidans are of distinct sexes. Among the spiders, 

 the male may generally be distinguished from the female by his 

 smaller size, longer limbs, and brighter colours. The essential and 



