STRUCTURE AND CLASSIFICATION. 



copulation takes place in the fall, and the female, living through 

 the winter, does not begin to lay eggs until some time in spring. 

 The eggs have at one end small openings termed micropyles, and 

 through these the spermatozoa find their way into the egg to 

 fertilize it. In the ovarian tubes a variable number of cells are 

 developed, and these grow rapidly, each cell eventually forming 

 an egg. The number of tubes and the number of cells in the 

 tubes vary within wide limits in the different species. In some 

 they are rigidly limited, and the insects are able to lay only a 

 definite number of eggs ; in others the cells are so numerous that 

 a definite number seems unlikely. Before the female has been 

 impregnated the ovarian tubes are very slender and occupy only a 

 little space in the abdomen. When the eggs develop, however, 

 the ovaries increase in size until, finally, the abdomen is almost 

 entirely occupied by them, and is often enormously distended. 



In the male the ovaries are replaced by the testes, which also 

 are more or less coiled tubular structures, and these tubes, like 

 the ovaries, unite to- 

 gether on each side into ^5- 

 a larger tube, which in 

 turn are combined into 

 a single organ, usually 

 more or less horny in 

 structure, — the penis. 



Reproduction among 

 insects is, therefore, in 

 its essentials, like that 

 of the higher animals. 

 The only difference is 

 that as the life period is 

 shorter, the eggs must 

 all be laid within a defi- 

 nite time, and they are 

 very much greater in 

 number. It further 

 proves that we have a 

 definite development in 



insects as in higher animals, and that with them also, like pro- 

 duces like, — that is to say, the product of the egg when fully de- 



Male organs of May-beetle. — One side only beyond 

 the ductus ejaculatorius, duct, ejac; glni., mucus 

 glands; ves. sem., s&ra.\xva\ vesicles; vas. def., vasa 

 deferentia. 



