144 NEW ZEALAND NATURE-STUDY BOOK 
egos are usually laid in a bag, made of strong silken fibre, 
which in some cases is carried about. The young Spiders 
grow with rapidity and in doing so are constantly obliged 
to cast their skin. After each fresh change of skin they 
are very helpless; and frequently fall a prey to their many 
enemies. Each change, moreover, is accompanied by an 
increase in size; after the last change they are full grown. 
Fig. 97.—Spider and Insect. 
A COMPARISON AND A CONTRAST. 
A comparison and contrast between the two groups of 
animals, Insects and Spiders, will bring out the following 
details. Both are furnished with jointed limbs, some of 
which end in claws. In both the body is soft and covered 
with a tough skin. In both the oxygen required for 
respiration is derived from the air, and both are able to 
spin silken threads. 
They differ (a) in the divisions of the body, the body 
of the Insect consisting of head, thorax, and abdomen, 
and that of the Spider of two segments only (the head and 
thorax being fused together) the head-thorax and abdomen ; 
(b) in the number of legs, the Insect having six and the 
Spider eight; (c) in the kind of appendages borne, the 
