THE EUROPEAN CORN BORER AND ITS CONTROL. 27 



at base, paler at free edge. INIandibles dark brown, protrude slightly. 

 Distal segments of antennse amber, otherwise colorless. 



Prothoracic shield averages 1.72 millimeters wide, more distinctly 

 divided than preceding instar. General color pale brown to pale yellow, 

 pohshed, with dark brown areas. Anterior border pale j-ellow. The 

 median posterior margin bears a triangular area, and two large irregular 

 areas are present in a shallow depression near the lateral corners of the 

 shield. The posterior and lateral marguis of the shield are dark brown. 

 Bases of setae surrounded by a distinct black ring. Venter of prothoracic 

 segment only slightly darker than venters of remaining segments. 



Prothoracic legs concolorous with head, mesothoracic legs dusky ex- 

 ternally, metathoracic legs pale amber. Abdominal and anal legs as 

 before. 



Sixth Instar (see Plate II, Fig. 10). — Average measurements of 9 

 individuals, four days after molting: Length, 19.95 millimeters; head 

 width, 2.19 millimeters. Body cylindrical, abdominal segments, except 

 9 and 10, crossed transversely bj- deep grooves. General color darker 

 than preceding instar, varying from dusky pale brown to dark brown or 

 pink. Median line narrow, dark brown and verj' distinct; subdorsal 

 line vague in outline, broad, pale brown or pink; lateral lines narrow, 

 pale brown. Tubercles medium and darker than general color of body, 

 more pronounced on thorax. Arrangement of prothoracic tubercles and 

 setse as before. Tubercles ia-i6, iia-iife and iv-v are coalescent on meso- 

 thorax and metathorax. Setae ia and iia are very much shorter than 

 setae ib and ii6. Seta v is very much shorter than seta iv, while setse iii 

 and vii are of medium length. Tubercles iv-v are coalescent on ab- 

 dominal segments 1 to 8, inclusive, situated below the spiracle on segments 

 1 to 7; below and slightly anterior to spiracle on segment 8. On dorsum 

 of abdominal segments 1 to 7, tubercles i and ii form a trapezoidal figure, 

 as before, while on dorsum of segment 8 these tubercles form nearly a 

 rectangular figure. Large corneous tubercle on dorsum of segment 9, 

 and preanal plate on dorsum of segment 10, with setal arrangement as 

 before. The setae on lateral anterior borders of prothoracic shield, setae 

 i& and ii6 of mesothorax and metathorax, the setse on dorsal tubercle of 

 segment 9, and the long setae on preanal plate are nearly twice as long as 

 any others present. 



Head polished brown, with pale brown areas on epicranial lobes. 

 Clypeus as before; average height, .27 millimeter, average width, .84 

 millimeter. Adfrontal pieces more distinct. Labrum, mandibles and 

 antennae as before. 



Prothoracic shield averages 2.34 millimeters wide. Colored areas on 

 shield similar to preceding instar, with additional small pale brown 

 depressions along each side of median line. The position and form of 

 these colored areas are variable. Ventei' of prothorax concolorous with 

 venters of remaining segments. 



Thoracic, abdominal and anal legs as before. 



