THE TRANSFORMATION OF INSECTS 45 



important characters for classification. In general they 

 consist, for the female, of the ovipositor, and in the male, of 

 external claspers and a central intromittent organ. 



Mating, in mkny insects, is accomplished during flight, 

 but this is by no means general. 



The eggs are fertilized in the oviduct, in most cases doubt- 

 less in the common duct, or in the vicinity of the sperma- 

 theca, and the spermatozoa enter the egg by way of a minute 

 pore termed the micropyle, located usually at one end of the 

 egg. 



THE TRANSFORMATION OF INSECTS. 



Insects, like all other animals, begin their develojiment 

 from an egg, not unlike any other forms. They pass through 

 a series of more or less distinct stages in development from 

 the egg to the mature or adult form. These stages are desig- 

 nated for the insects in general as egg, larva, pupa, and 

 imago. While differing greatly in the definiteness of separa- 

 tion between the different stages, it is convenient to use 

 these terms in tracing the life history of any insect and in 

 describing the character of each of the stages somewhat 

 more in detail and considering the bearing in the connection 

 with economic treatment. 



The egg is generally a c()m])aratively small object, con- 

 taining a considerable portion of yolk material and i)rovid- 

 ing for some degree of development before hatching. The 

 shapes differ greatly in the different forms, perhaps the 

 most common, and consequently the most fundamental, 

 being an elongate, oval shape. Spherical forms are by no 

 means scarce, and flattened spherical, elongated spherical, 

 or even linear or cylindrical forms are very common. The 

 greater difference may be noted in the character of the 

 surface of the eggshell, which may be minutely reticulated, 

 striated, punctin*ed, beset with fine spines, and frequently 

 having a distinct lid through which the larvae are to 

 escape. They may be placed loosely in suitable locations, 

 attached simply by a glutinous secretion, forced into the 

 tissue by the ovipositor, etc. For aquatic species they may 



