STRUCTURE OF INSECTS AND ARACHNIDA. 



105 



life, which was interrupted at a very early period. In some 

 tribes, however, the general form is the same from the first, 

 and the wings are the only parts deficient ; these gradually 



Antennae _ 



Eyes 



Head 



1st pair of Legs 



1st pair of Wings - 

 2nd pair of Legs - 



2nd pair of Wings " 

 3rd pair of Legs 



Tibia 



Tarsus 



Abdomen 



Fig. 45. SKELETON OF AN INSECT. 



make their appearance, and the insect is then complete. Such 

 is the case with the Grasshopper and Cricket; and a change 

 of this kind is termed an incomplete metamorphosis. 



98. The animals of the class ARACHNIDA, which includes 

 the spiders, scorpions, and mites, are, like Insects, articulated, 

 breathing air, and possessing legs, but the number of these 

 legs is never less than eight; there is an entire absence of 

 wings, and the head is united with the thorax, so that the 

 body seems to be formed of two principal divisions, the 

 cephalo-thorax (as it is termed), and the abdomen. In fig. 46 

 we have a representation of the arrangement of the parts con- 



