360 W. D. FUNKHOUSER 



they are homologous with the harpes of the Lepidoptera can ])e determined 

 only by a comparative study of the two orders. 



The oedagus, or penis sheath, is a heavy, partly chitinized covering 

 for the penis. It is apparently of one piece and does not show the seg- 

 ments described for this organ in other orders of insects. In composition 

 it is substantial enough to withstand the boiling and clearing necessary 

 for examination under the microscope, and usually stands out well in such 

 mounts. The oedagus seems to arise from the very base of the ninth 

 segment, between the bases of the lateral valves and the sternal plate. 

 Such an origin would agree with that found for the organ in certain beetles, 

 and fairly well with the same structure in other orders. Muir (1915:151) 

 states: ''The oedeagus arises as a tubular organ at the base of an inter- 

 segmental invagination between the ninth and tenth sternites." 



The function of the organ is undoul^tedly protective, and it maj^ be noted 

 that practically no other protection is afforded to the penis since the entire 

 genital chamber is so openly exposed. The oedagus itself is apparently 

 of sufficient strength and rigidity to need no protection, altho in other 

 orders it is generally covered by some parts of the genital chamber. In 

 this connection Sharp (1890:421^22) states: 



It appears to be a great comfort or advantage to insects to be able to withdraw and cover 

 over some of the sensitive parts of the body during repose, or when the parts are not in 



use It is therefore quite consistent with what we find to obtain in insect economy 



that the aUmentary canal . . . should be made to protect the oedeagus, and the fact 

 justifies us to some extent in inferring that the oedeagus, or some part of it, is a sensitive 

 organ; but it is, on the other hand, equally probable that the delicate structures of the oedeagus 

 are covered simply to preserve them from injury. 



In shape the oedagus is uniformly curved, bending upward and for- 

 ward so that its apex points toward the rectum. It varies greatly in 

 diameter in different genera and the tip is inclined to be much modified. 

 Often the entire organ is gradually acuminate and sharp at the extremity 

 (Plate XXXIX, 6); again, the tip may be swollen and surmounted by a 

 knob-like projection (Plate xxxix, 9). These two forms are the ones 

 used by Fowler (1894-97) to separate the genera Ceresa and Stictocephala, 

 and are believed to be sufficient characters for such distinction. In 

 Stictocephala the apex of the oedagus is so liroadly expanded, ])ell-shaped, 

 and prominent as to be easily determined from a lateral view, and should 

 serve as an excellent taxonomic character. The organ may 1)e nnich 

 swollen just below the apex (Plate xxxix, 18, 20) — and occasionally 



