THE ROUGH-HEADED CORN STALK-BEETLE 



17 



Fig. 5. — Ventral view of posterior end of abdomen of 

 male pupa of Euetheola rugiceps, showing sexual 

 characters. (Drawn by Henry Fox) 



pupa stage the larva lies on its back, in a slightly curved position, 

 in the cavity formed by its movement in the soil. While still inclosed 

 in the old integument, the larva undergoes its transformation into 

 a pupa. This process is initiated by the withdrawal of the internal 

 mass of the body from the larval integument at its hind end, which 

 becomes greatly shriveled. Finally, when the pupal body has been 

 formed, the larval skin 

 splits along the dorsal 

 line, revealing the fully 

 formed pupa within. 

 The latter frequently 

 passes its entire exist- 

 ence inclosed within the 

 split larval skin. 



PUPA 



DESCRIPTION 



The pupa of Euethe- 

 ola rugiceps measures on 

 the average about 15 

 millimeters in length, 

 and is pale buff. Its 

 general form is shown in Plate IV, A, and certain of its structural 

 features in Figures 4, 5, and 6, but probably its most distinctive pecul- 

 iarities are those of the mouth parts (fig. 4). The mandibles are 

 relatively stout, roughly triangular in outline, and with the apex 

 forming a rounded angle. The labrum is quite wide transversely, and 

 has its free edges regularly and evenly arcuate. The maxillary palpi 



are short, conical structures which 

 are nearly vertical in position and 

 have their tips projecting but 

 slightly below the level occupied 

 by the other mouth parts. 



Other distinctive characters are 

 afforded by the shape of the post- 

 coxal process of the presternum, 

 which is rather short, blunt, and 

 constricted near the middle, and 

 by the elytral pads, which are 

 smooth, or, at most, only ob- 

 scurely costate. 



Sexual characters in the pupa 

 occur in the ventral surface of the 

 last abdominal segment. In the 

 male this bears a prominent hemi- 

 spheric protuberance, the apex of which is slightly indented (fig. 5) ; 

 in the female this structure is lacking, but instead there is a minute 

 median projection of the anterior border of this segment into the 

 segment in front (fig. 6). This process shows a pair of lateral, more 

 fully chitinized ;ireas which probably correspond to the genital plate 

 of the adult female. 



94051°— 24 3 



Fig. 6. — Ventral view of posterior end of 

 abdomen of female pupa of Euetheola 

 rugiceps, showing sexual characters. 

 (Drawn by Henry Fox) 



