28 



INSECT TRANSFORMATION 



15 ed) passes downwards to open on the ninth abdominal 

 sternum. This male reproductive opening is surrounded by a 

 complex set of chitinous processes and hooks known as the 

 genital armature. 



Our very superficial survey of the adult grasshopper's struc- 

 ture shows that the insect is a creature of great complexity, 

 " highly organized " as the naturalist often expresses it. We 

 have now to consider how this and other animals formed on the 

 same general plan, are built up from simple beginnings, passing 

 in the process through a series of changes. In describing the 



sp 



FIG. 15. MALE REPRODUCTIVE ORGANS. 



T, testes ; vd, vas deferens ; sv, seminal vesicles ; agl, acces- 

 sory glands ; ed, ejaculatory duct. Magnified and diagram- 

 matic, sp, a spermatozoon. x 1,500. In part after 

 Comstock. 



life-history of any animal, it is convenient to distinguish 

 between the development in the egg or before birth (when the 

 creature is called an embryo) and the post-embryonic growth 

 (subsequent to hatching or birth) which may be accompanied 

 by slight or by great changes of form. In our study of growth 

 and change during insect life-histories, it is to the period after 

 hatching or birth that attention will be mainly directed, because 

 the post -embryonic development of insects is such a marked 

 feature in their lives. The embryonic development of insects 

 affords a vast field of study at once difficult and fascinating, 

 so that its adequate treatment would be impossible within 



