THE STUDY OF INSECT LIFE 17 



skin produces fresh changes and the appearance 

 of new structures, alterations almost equal to 

 those peculiar to the stated periods of metamor- 

 phosis, their function is very closely allied, if 

 not identical, to incomplete metamorphosis. In 

 the Arachnida, the body is divided into an 

 anterior region the cephalothorax representing 

 both head and thorax, which in a large pro- 

 portion are intimately united, and a posterior 

 region or abdomen. In some cases these two 

 regions are united, and wings are never present. 

 Respiration may be carried on by sac-like 

 depressions in the body called pulmonary sacs 

 or book-lungs or by true tracheae analogous to 

 those of the Insects. 



The Scorpions are the largest and most 

 formidable members of the Arachnida, and are 

 chiefly confined to the tropics, though a few 

 species are to be found in Southern Europe. 

 The cephalothorax of the Scorpion has- its upper 

 surface partially covered by a shield-like horny 

 plate, upon which may be seen from three to six 

 pairs of simple eyes, a pair of extra size being 

 placed close to the middle line of the shield. The 

 slender posterior part of the body bears a 

 terminal appendage, the caudal spine or sting, 

 which is swollen at its base and sharply pointed 

 at the apex. The swollen part contains a pair of 

 glands secreting a poisonous fluid, which is 

 carried by ducts to the acutely pointed and 

 perforated apex of the sting. If we examine the 

 under surface of a Scorpion, we shall find on 

 each side of the very small aperture of the mouth, 

 curious triple-jointed biting appendages, called 



