WOOD-BORING BEETLES 3 



that are often called insects, though not really such, 

 it will be best first of all briefly to indicate what 

 kind of creature is implied zoologically by the term 

 "insect." 



Insects constitute a class of the animal kingdom dis- 

 tinguished from other invertebrate animals by having 

 the body divided into three parts, head, thorax, and 

 abdomen, and by possessing in the adult condition six 

 legs disposed in three pairs, and usually four wings as 

 well. The head carries first the mouth organs, which 

 vary much in different groups, and will be particularly 

 described hereafter, and secondly the organs of sense, 

 consisting chiefly of the eyes and antennae, the latter 

 being that pair of long jointed appendages popularly 

 known as " horns." The thorax carries the legs beneath 

 and the wings above. The abdomen carries no legs in 

 the adult insect, but has frequently in the females a 

 more or less complicated apparatus at the end, some- 

 times looking like a long tail, and used for depositing 

 the eggs, and therefore called an ovipositor. Most 

 insects also pass through a series of transformations 

 during the course of their life, which are called col- 

 lectively "metamorphoses." They are first the egg; 

 secondly the larva, grub, or caterpillar; thirdly the 

 chrysalis or pupa; and fourthly the perfect insect or 

 imago. There are other characteristics of a less obvious 

 nature, but these are in most cases sufficient for practical 

 purposes, and will enable one to determine what animals 

 are insects and what are not. The class is subdivided, 

 according to the nature of the wings, the feeding appa- 

 ratus, and the life history, into groups called " orders ; " 

 and our household insects are so varied in structure that 

 there is not a single important order unrepresented in 

 domestic entomology. 



