1922] Walker: Structure of Orthopteroid Insects 23 



The Genitalia. 



The male genitalia of the Orthoptera exhibit an even wider 

 range of variation than do those of the females, but, as in the 

 latter, a fundamentally similar plan of structure can be traced 

 in these organs throughout the order, except in a few cases in 

 which they are very degenerate. This plan of structure is 

 characteristic of the Orthoptera seyis. str., and is widely different 

 from other orthopteroid groups. Its most distinctive feature 

 is the presence of a pouch or sac into which the ejaculatory duct 

 opens and from the roof or walls of which the parameres arise. 

 The sac has the function in very many forms of a spermatophore 

 sac, and this is probably its primitive purpose. 



The penis is commonly large and prominent and its orifice 

 is generally wide with folded walls, there being usually a pair 

 of ventral lobes, or sometimes a single one. The titillators, or 

 parameres, as I believe them to be, are primitively dorso- 

 terminal in position, but their bases are usually more or less 

 retracted, so that they may appear to have no relation to the 

 dorsal surface, being in some cases almost completely concealed 

 from view. 



Owing to the shifting of the genital area from a ventral to a 

 posterior position by the elongation of the ninth sternum the 

 penis comes to lie under the paraprocts, and is also typically 

 under cover of a projecting plate, the pseudosternite, which 

 forms an arch over its base and serves for the origin of muscles 

 concerned in its movements. This arch is often prolonged on 

 each side into a pair of arms, the rami, partly encircling the 

 penis at its base, and more or less produced inwardly into 

 processes, which may be termed endapophyses, for the attach- 

 ment of muscles concerned in the movements of the penis. 

 Sometimes the endapophyses may be separated from the 

 pseudosternite and are present in many forms (Tettigoniidae), in 

 which the latter has disappeared. In the Acridoidea these 

 structures are further complicated, but their peculiarities need 

 not be considered here. 



In addition to the structures just described there may be 

 mentioned also a pair of glandular pouches, lined with chitin, 

 which open separately or by a common duct into the ejaculatory 

 duct, close to its termination in the spermatophore sac. It is 

 sometimes represented by a single sac and is probably connected 



