n6 



ENTOMOLOGY 



and-left hermaphroditism in 153 individuals. In other instances the 

 antero-posterior kind may occur, as when the fore wings are of one sex 

 and the hind wings of the other; rarely, the characters of the two sexes 

 are intermingled. 



Hermaphroditic insects are such rarities that very few of them have 

 been sacrificed to the dissecting needle in order to determine whether the 



phenomenon involves the primary organs 

 as well as the secondary sexual characters. 

 Where dissections have been made it has 

 been found usually that hermaphroditism 

 does extend to the reproductive organs them- 



FIG. 184. Types of ovarian 

 tubes. A, without nutritive cells; 

 B, with alternating nutritive and 

 egg-cells; C, with terminal nutri- 

 tive chamber; c, terminal cham- 

 ber; e, egg-cell; ep, follicle epi- 

 thelium; /, terminal filament; s, 

 strands connecting ova with nutri- 

 tive chamber; y, yolk, or nutritive 

 cells. From Lang's Lehrbuch. 



FIG. 185. Ovum of a butterfly, Vanessa, in its 

 follicle, e, follicle epithelium; g, germinal vesicle; 

 n, branching nucleus of nutritive cell; 0, ovum. 

 After WOODWORTH. 



selves. Thus a butterfly with male wings 

 on the right side and female wings on the 

 left would have a testis on the right side of 

 the abdomen and an ovary on the left side. 



Parthenogenesis. Reproduction without fertilization is a normal 

 phenomenon in not a few insects. This parthenogenesis may easily be 

 observed in plant lice. In these insects there are many successive broods 

 consisting of females only, which bring forth living young; at definite 

 intervals, however, and usually in autumn, males appear also, and ferti- 

 lized eggs are laid which last over winter. This cyclic reproduction, by 

 the way, is known as heterogeny. Among Hymenoptera, parthenogenesis 

 is prevalent, usually alternating with sexual reproduction, as in many 



