THE JOINTED ANIMALS 



a jerk, still further entangling the prey by bringing other threads into contact with- 

 it. If necessary, the net is snapped more than once, and when the spider feels 

 that the insect is enveloped, it crawls leisurely along the web to devour it. The 

 genus is common to Europe and North America. The other members of this tribe 

 belonging to the family Argiopidce have no cribellum nor calamistrum. Their webs- 

 vary in form, but are mostly of the orb type, consisting of straight threads radi- 

 ating from a centre to the foundation lines, which are stretched from one point of 



support to another, and of a spiral line passing from the 

 centre to the circumference, affording support to the 

 radial lines and partly filling in the spaces between them. 

 The spiral line is the principal part of the web involved 

 in the capture of insects, many of its strands being 

 covered with a series of gummy drops like beads on a 

 string, which greatly hamper the movements of a cap- 

 tured insect. The presence and position of an insect in 

 the web is perceived solely by the delicate sense of touch 



in the spider's feet, and for this reason the spider either 

 COMMON CROSS SPIDER, Aran- takes hs stand in the centre of the web where ks 



eus diadema (natural size). 



eight legs can command all the radii, or else beneath 



some leaf at the end of a long thread passing from the centre to its place of 

 concealment. In cases of danger the spiders either drop to the ground by a 

 thread, or, seizing the web with the tips of their feet, start spinning the body 

 round and round in circles and causing the web to oscillate rapidly until it and 

 its"occupant almost disappear from view. The commonest British members of the 

 family belong to the genus Araneus, of which the cross or garden spider {A, 

 diadema} is so abundant in gardens late in summer and autumn. Some of the 

 tropical forms, such as Nephila, are of enormous size, and construct huge webs 

 strong enough, it is said, to arrest the flight of small birds. The males are veri- 

 table pygmies, as compared with the females. Also belonging to the family are 

 those curious tropical spiders of the genus Gastracantha, which are protected 

 from enemies by having the integument of the abdomen hard, horny, and armed 

 with spines. The figure on p. 3197 of a species of Tetragnatha represents 

 another tolerably com- 

 mon member of this 

 family. It is char- 

 acterized by its long 

 and slender abdomen, 

 and enormously strong 

 projecting mandibles. 



We now come to '^^S^^^lIK^^:. .^"~*^ii&*M?JH&&!i& - 



SIDE WALKING SPIDER (Xyshcus vjaticus). Female, left-nand figure ; male, 

 right-hand figure (enlarged). 



ing in that they obtain 

 their prey by hunting 

 instead of constructing 



