OUTLINES OF ENTOMOLOGY. 17 



The salivary fluid is used by the bee and wasp to moisten and 

 cement the particles of sap and wood from which the brood and honey 

 cells are made. 



The odoriferous organs are of various construction, and are located 

 in some species in one part of the body, and in others in another. They 

 are designed in some cases as a means of attraction between the sexes ; 

 in others to repel the attacks of their enemies. 



The poison glands are situated sometimes in the mouth, but more 

 frequently at the tip of the abdomen. The poison is of the nature of 

 an acid, and is injected into wounds made by the jaws or by the piercer 

 or sting. Its use is to ward off or revenge the attacks of foes and to 

 paralyze or kill the prey required by the insect for its own food or as 

 food for its young. 



CHAPTER VI. 



TRANSFORMATION OF INSECTS. 



Transformations of a lepidopterous insect, the corn 

 worm or boll worm (Heliothes armigera), after Riley ; a, b, 

 egg, magnified; c, larvse; d, pupa; e /, imago or moth. 



The transformations or metamorphoses of insects have been already 

 alluded to as one of their most peculiar and interesting characteristics. 

 These are certain changes of form and habit by which the life of every 

 insect, after hatching, is divided into three more or less distinct periods 

 or stages. 



Transformation may be either complete or partial. It is complete when 

 the appearance and general habit of the insect is so different at each 

 stage of its existence, that only experience enables us to recognize the 

 various forms as pertaining to the same individual ; and partial when 

 the insect retains essentially the same form and habit during life, its 



