156 KANSAS UNIVERSITY SCIENCE BULLETIN. 



The typical structure of an ovipositor is described in the fol- 

 lowing quotation from Packard: "Morphologically, the ovi- 

 positor is composed of three pairs of un jointed styles (rhab- 

 dites of Lacaze-Duthiers, gonapophyses of Huxley) , which are 

 closely appressed to or sheathed within each other, the eggs 

 passing out from the end of the oviduct, which lies, as Dewitz 

 states, between the two styles of the lowest or innermost pair 

 and under the cross-bars or at the base of the stylets men- 

 tioned ; the styles or blades spreading to allow of the passage 

 of the egg." 



The structure of this organ I find to be second in interest 

 only to the mouth parts. It is more complicated in structure 

 than those parts in the cicada, but the homologies between the 

 two can be worked out in part, as will be seen later. It is very 

 similar in most points to the ovipositor in the Aleurodidae. 



Lack of material has confined my work to postembryonic 

 studies. There has been much investigation on the segmental 

 origin of the ovipositor parts, the researches of Wheeler and 

 Heymons being of chief importance. Wheeler (1892), who 

 studied orthopteran embryology, holds for the "direct con- 

 tinuity of the embryonic appendages with the gonapophyses," 

 while Heymons (1899), from studies in Heteroptera and 

 Homoptera, considers these gonapophyses as hypodermal out- 

 growths. However, it is not my purpose to discuss these ques- 

 tions, but to treat of the anatomy and homologies of the parts. 



A specimen of Pachypsylla female, mounted in balsam after 

 having been thoroughly boiled in caustic potash and cleared, 

 showed, when viewed from the side, the relative position of 

 the ovipositor as regards supra-anal and subgenital plates, and 

 the posterior abdominal segments (30A). The ovipositor is 

 seen to be an elongate organ with dorsal and ventral outlines 

 about parallel. It measures in length about 0.82 mm., in 

 greatest width about 0.19 mm., and in thickness less than half 

 that of width. The caudal extremity is acutely pointed, this 

 portion bending dorsad, then caudad, with its apex extending 

 caudad even with the tip of the subgenital plate, while the 

 supra-anal plate extends caudad from this apex 0.11 mm. in the 

 specimen described. The proximal or cephalic end of the ovi- 

 positor is composed of several sclerites of irregular form, to be 

 described later, the ends of which project 0.16 mm. beyond a 

 line joining the bases of the enclosing external plates to a 



