458 LECTURE XIX. 



rest, and connected, in Calamistrum, with a kind of comb attached 



to the metatarsus of the hind legs. Six, however, is the ordinary 



number of spinnerets in the spiders, two of which are longer than 



the others. The secretion does not issue by a simple outlet, but by 



a multitude of microscopic pores {Jig. 171), 



which, in the shorter pairs of spinnerets, are 



prolonged from the terminal surface upon minute 



processes. If you throw a little dust upon the 



web of any of the orbitele spiders, of the Epeira 



diadema for example, you may observe that it 



adheres to the spiral, but not to the radiated, 



threads ; for the spiral thread is beset with minute 



viscid globules. Lyonnet supposed that the ad- Upp^l^lf^^t. 



hesive threads issued from the tubular, and the Tegenarm civius. 



others from the sessile orifices. The secretion is a glutinous fluid, 



insoluble in water, and quickly drying in air ; some species, as Ar- 



gyroneta aquatica, spread their nets habitually under water. 



The degree and mode in which spiders exercise this singular 

 secreting faculty varies considerably in the different species. Some, 

 as the Cluhiones, 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 cemen- 

 taria lines a subterraneous burrow with the same substance, and 

 manufactures a close-fitting trap-door of cemented earth lined with 

 silk, and so attached 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, cba- 

 racterised by their habits, places the principal varieties of their 

 webs in a very concise point of view. 



The Cursores, Saltatores, and LaterigradcB, 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 Filitelce are remarkable for the long threads of silk which 

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



* Histoire des Araneides. 



