468 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1925 



SO shaded as to appear very much so. The small flat ventral area 

 of the larva is pale and white, and is the only portion where any 

 movement can possibly occur, the rest being a solid chitinous cap. 

 Constructed as it is to permit this soft area to be absolutely cov- 

 ered and hidden on the surface on which the larva rests, one is sur- 

 prised at its widening out above this area, quite regularly until, 

 at a sudden sharp margin, the sides meet the flat top. The brown 

 marginal marks are apparently two to a segment, certainly so at 

 the sides where the}^ are largest, and where a faint depression along 

 the sloping sides seems to mark each segmental division. To see 

 this, however, requires close examination, and some might say a 

 little imagination. 



Turning the larva over again to examine the back more carefully, 

 we find the margin very sharp and slightly browner than the terra- 

 cotta center. Laterally and posteriorly it is a little hollowed within 

 the margin. Across the middle are three very distinct lines, darker 

 in color, and with the surface in front decidedly higher than behind. 

 They occupy the middle two-thirds of the surface, but do not invade 

 the fourths on each side next the margin. In front and behind 

 these the indications of the segmental divisions are very obscure. 

 A faint indication of a dorsal ridge exists in front of these lines. 

 There are also a number of dots that appear to be obsolete hair 

 points, arranged in some degree as a transverse line across each seg- 

 ment, but with outlines enough to make such a statement a little 

 doubtful or even misleading. The two segments marked out by the 

 dorsal lines are the fourth and fifth abdominal. 



The character of the sharp margin of the dorsal area needs a 

 little more definite description. In the first place the out-sloping 

 sides for their top millimeter cease to slope, but become vertical ; 

 then inside the sharp border the surface descends again steeply so 

 as to form a sharp raised border to the central area. In front 

 the inner slope soon bends into the flat dorsal area; behind it does 

 so more slowly, resulting in the hollow before noticed. Around 

 this portion there is, inside as well as outside the sharp margin, 

 a breadth of about 1 mm., differentiated by a slight line from the 

 general dorsal surface. 



Seen microscopically, the whole surface consists of very minute 

 raised dots, each carrying a fine point; on the marginal flange sur- 

 rounding the dorsum these are modified into an arrangement that 

 has just the appearance of overlapping fish scales. 



The spiracles are difficult to find ; in fact, Doctor Chapman 

 failed to liiid (he thoracic spiracle. The abdominal spiracles are 

 precisely where they are in tlie small larva. They are very small, 

 and differ little in appearance from the hair-dots noted above. 



