SCORPIONS, SPIDERS, ETC. 299 



secrete a viscid fluid, whicii becomes tough as silk as 

 soon as it is exuded, and is fashioned by the spinnerets and 

 legs into webs, snares, and other structures for trapping or 

 impeding prey, or into nests or " cocoons " for protecting the 

 eggs and young. 



The breathing-organs also open on the ventral surface 

 of the abdomen. In most spiders these consist (i) of two 

 lung-sacks, like those of scorpions, which open, anteriorly, one 

 on either side of the genital pore, and (2) of two or more 

 tracheal trunks which open just in front of the spinnerets. 

 In some spiders instead of the trachese there is a second 

 pair of lung-sacks lying immediately behind the first pair. 



The mouth is a minute pore sunk deeply behind the 

 chelicerae. The food — except in the case of certain very 

 large tropical spiders — consists of insects, which are sucked 

 dry after being killed by the poison-fangs. 



The female spider, which greatly exceeds the male in 

 size, produces eggs, in batches, which are enveloped in a 

 silky nest, or "cocoon," and are often guarded or ^carried 

 about by the mother. 



Some spiders chase their prey, and others lie in wait for 

 it. Of the latter some are so coloured as to escape detection, 

 some hide in burrows, and others spin webs and pitfalls of 

 various kinds in which the prey is entangled. A few species 

 live in fresh water, and there are several marine species. 



The venom of some spiders is particularly toxic, and the 

 bite of some species is said to cause serious and even fatal 

 results to man. This is said to be particularly the case with 

 the species of Lathrodectus which are found in all tropical 

 and subtropical latitudes : they are spiders of no great size, 

 with a globular abdomen, which is often striped, or spotted, 

 or brightly coloured, and longish but fairly stout legs. 



The Araneida are divisible into two sections, namely 

 (l) MesothelcB, in which the abdomen is distinctly divided, 

 dorsally, into 9 segments, and the spinnerets are situated 

 in the middle of its ventral surface ; and (2) Opisthothelce, in 

 which the abdomen is not segmented, and the spinnerets 

 are posterior. 



The Mesothelce include a single genus, which is restricted 

 to the Oriental Region. 



