DIFFERENCE OF THE SEXES. 37 



by the penetration of some of its elements into their 

 substance, the impregnation of the eggs is produced. 

 In many of the lower marine animals the male and 

 female organs are united in the same individual in 

 such a way that the contents of the former can come 

 in contact with the eggs, and thus efiect their im- 

 pregnation ; these animals are called true hermaphro- 

 dites. In Insects we sometimes meet with herma- 

 phrodites, in which the organs of both sexes are 

 present, but these are rarely, if ever, capable of self- 

 impregnation. In most cases, indeed, the so-called 

 hermaphrodites of insects are merely male or female 

 individuals, exhibiting a union of certain external 

 peculiarities which are usually characteristic of one 

 sex only. As a knowledge of these external sexual 

 characters is of considerable importance in the study 

 of Insects, it will not be amiss if we devote a little 

 attention to them here. 



In most insects we find that the female is larger, 

 and especially more bulky than the male ; whilst the 

 latter frequently has certain portions of the limbs, or 

 other appendages, more largely developed than his 

 partner. The female also is often furnished with a 

 peculiar appendage at the apex of the abdomen, which 

 serves for the introduction of the e^^ into its appro- 

 priate situation, and is thence called an ovipositor. 

 Even when this organ is not present, there is often a 

 difference in the form of the last segments of the 

 abdomen in the two sexes, which enables us imme- 

 diately to distinguish the males from the females. 



Of the peculiar characters presented by the males, 

 none is of more importance than the possession of 

 perfect wings by the males of many insects, the 

 females of which are either entu'ely destitute of those 



