10 



BULLETIN 539, U. S. DEPARTMENT OF AGRICULTURE. 



Fig. 4.— The lesser 

 corn stalk-borer: 

 Pupa. Greatly en- 

 larged. (Original.) 



pale in the upper angle, extending over two-thirds of height of head (0.43 mm.). 



Paraelypeal pieces prominent, sutures converging at the beginning of intersection 

 point of head lobes on vertex; setse pale, stiff, pale around base; 

 proximal parts of antennae pale whitish, distal amber; labrum pale 

 amber, width 0.32 mm.; mandibles dark red, black at tips. Cervical 

 shield dark brown, width 1.49 mm., length 0.93 mm.; pale line on 

 meson extending across the shield, coming to a point before; ex- 

 tending over head to intersection of lobes. Body Nile green, pre- 

 vailing color on the dorsum greenish white, which almost breaks 

 up completely the dark brown transverse bands; longitudinal 

 stripes conspicuous, dark brown, somewhat broken. Tubercles 

 "ia" and "ib" of joint 3 small, setse short, "iia" and "iib" small, 

 seta long; "ia" and "ib" of joint 4, small, seta short, "iia" and 

 "iib " small, seta long, caudad of latter is dusky patch, somewhat 

 polished; on joints 3 and 4 "iii" is caudo-laterad of "iib, " distant, 

 "iv" is cephalad and slightly laterad of "iii," distant, "v" 

 cephalo-laterad of "iv," well separated; "iv-v" is coalescent on 

 joints 5 to 13, inclusive, arrangement as before; on joint 13 "vi" 

 is near "v"; on joints 12 and 13 "ii" is much nearer meson than 

 "i," on joint 11 "i" and "ii" arranged in form of square. All 



segments slightly swollen except last two; transverse grooves prominent. Thoracic 



legs dusky; abdominal prolegs pale. 



PUPA. 



The pupa (fig. 4) when freshly formed is pale green, yellowish on abdominal seg- 

 ments; later brown and just preceding emergence of adult uniform black; lustrous; 

 delicate; length 8.1 mm., width 2 mm. Spiracles ellipsoidal, prominent, except on 

 joint 12, obsolete. Dorsum of terminal segment has slight elevation or hump which 

 slopes abruptly posteriorly and forms the obtuse tip. Anterior portion of this eleva- 

 tion corneous, rugose, and black. At tip is a row of six hooked spines arranged trans- 

 versely, about 0.17 mm. in length. Tip of the male pupa is rounded, that of the 

 female pupa irregular. Other sexual differences in pupal stage shown in figure 5, a 

 and b. Abdominal segments 1 to 7, inclusive, densely and finely pitted on dorsum, 

 very abundant and scattered almost over whole surface of first four segments, scant 

 and restricted to anterior border of last three. 



COCOON. 



The cocoon is cylindrical, compact, 15.9 mm. in length, and 5.9 mm. in diameter, 

 oval in outline, frequently supplied with exit tube at an angle of about 145°; 23.9 to 

 30 mm. in length and 4 mm. in diameter; lined 

 throughout on inside very smoothly with silk 

 and covered without with sand and dirt particles. 

 (PI. II, figs. 3 and 4.) 



ADULT, i 



Expanse 17-22 mm. Head brown to blackish. 

 Labial palpi erect, not recurved; somewhat 

 Longer in the male than in the female and more 

 slender, heavily scaled, lying close together on 

 the shining crest which is hollowed out for 

 them; somewhat clavate toward the tip, end 

 member very short, about one-eighth the middle; 

 groove for the pale papillary tufts reaching 

 almost to the apex and very deeply impressed, 

 within bearing a longitudinal white stripe which broadens somewhat at the end oi 



Fig. 5.— The lesser corn stalk-borer. 

 Comparison of terminal segments of 

 male and female pupae showing sexual 

 differences: o, Female; 6, male. Greatly 

 enlarged. (Original.) 



Basal segments pale gray outside, 



Compiled from descriptions of Zcller and Hulst by the junior author. 



