156 AN INTRODUCTION TO ENTOMOLOGY 



present, but the sense-fiber of the sense-cell pierces the bottom of the 

 cone and enters the round, oblong, or slitlike pore-aperture. "It is 

 thus seen that the cytoplasm in the peripheral end of the sense- 

 fiber conies in direct contact with the air containing odorous par- 

 ticles and that odors do not have to pass through a hard membrane 

 in order to stimulate the sense-cell as is claimed for the antennal 

 organs". 



XV. THE REPRODUCTIVE ORGANS 



a. THE GENERAL FEATURES 



In insects the sexes are normally distinct except in a single genus 

 of wingless, very aberrant Diptera, Termitoxinia, the members of 

 which live in the nests of Termites ; these have been found to be her- 

 maphroditic. 



Individuals in which one side has the external characters of the 

 male and the other those of the female are not rare ; such an individual 

 is termed a gyndndromorph; in some gynandromorphs, both testes 

 and ovaries are present but in no case are both functional ; these there- 

 fore are not true hermaphrodites. 



In females the essential reproductive organs consist of a pair of 

 ovaries, the organs in which the ova or eggs are developed, and a tube 

 leading from each ovary to an external opening, the oviduct. In the 

 male, the essential reproductive organs are a pair of testes, in which 

 the spermatozoa are developed and a tube leading from each testis to 

 an external opening, the vas defer ens. In addition to these essential 

 organs, there are in most insects accessory organs, these consist of 

 glands and of reservoirs for the reproductive elements. 



The form of the essential reproductive organs and the number and 

 form of the accessory organs vary greatly in different insects. It is 

 impossible to indicate the extent of these variations in the limited 

 space that can be devoted to this subject in this work. Instead of 

 attempting this it seems more profitable to indicate by diagrams, one 

 for each sex, the relations of the accessory organs that may exist to 

 the essential organs. 



In adult insects the external opening of the reproductive organs is 

 on the ventral side of the abdomen near the caudal end of the body. 

 The position of the opening appears to differ in different insects and in 

 some cases in the two sexes of the same species. The lack of uni- 

 formity in the published accounts bearing on this point is partly due 

 to differences in numbering the abdominal segments; some authors 

 describing the last segment of the abdomen as the tenth while others 



