SPIDERS 171 



Class II. ARACHNIDA Scorpions, Spiders, Mites, etc. 



This is a group of animals which are distinguished from insects by having 

 only two divisions of the body the cephalo-thorax (head and thorax united) 

 and the abdomen. There are usually four pairs of walking legs on the thorax. 

 Insects, on the other hand, have three divisions of the body head, thorax, 

 and abdomen and only three pairs of walking legs. There are no true Scorpions 

 in this country, and therefore we pass on to the 



SPIDERS, 



of which there are about 500 British species, divided into two tribes : (i) Octo- 

 noculina (eight eyes), and (2) Senoculina (six eyes). Their general appearance 

 needs no description, but certain points are worth noting. In the first place, 

 the young when once hatched pass through no larval or pupal stages like 

 insects, but are perfect specimens of the adult spider, though very small. They 

 " moult " or change their skins several times before reaching maturity, and 

 frequently reproduce at this time any part which has been broken off or injured. 

 They have been known to live three or four years, and the female to produce 

 several broods, but hi most cases they do not long survive the laying of eggs. 

 The eyes of spiders are simple, and not compound, as is the case with those of 

 insects, and are either six or eight (in British species). They vary in size and 

 in grouping, thus forming an important detail in distinguishing the different 

 genera. It is worth while to examine them under a microscope or magnifying 

 glass to realize their brilliancy and colour, some being of a beautiful ruby 



colour. Some are set in parallel rows on the " forehead " thus : 00*0 



9 



in oval or circular form * *, or in pairs 9 * , and, in fact, in many 

 other combinations. Below the eyes and above the mouth you will notice 

 the fakes, or poison fangs, formidable weapons, of which the fang closes 

 down upon the base into a groove like a pocket knife. With these the spider 

 catches, holds, and kills its prey, the poison being contained in a gland at the 

 base, and emitted through a small opening at the point of the fang. The legs 

 have seven joints, and on the foot are two or more curved claws, sometimes 

 plain, sometimes toothed like a comb. At the end of the abdomen are the 

 spinnerets or organs of spinning, in two, three, or four pairs. These contain 

 many minute openings through which the silk issues as a sticky fluid, which 

 hardens immediately on contact with the air. The breathing apparatus 

 consists of two or four yellowish or brownish scales or gills slit at then* hinder 

 edge. 



The web of the Garden Spider is a most wonderful construction, and there 

 is no more interesting work to be observed than the actual building of this 

 beautiful snare. First a number of irregular threads are fixed as a roughly 

 four-sided framework to certain firm points, and these are furnished with other 



