l6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 56 



THE PILOSITY 



The anterior marginal vein bears large and small hairs which are 

 directed obliquely forward, upward and outward. On its distal part 

 the large hairs form two rows ; proximally, the large hairs increase 

 in number and size, and inside the notch (pi. 6, figs. i8, 19, si) this 

 vein is closely set with large bristles. The small hairs are not nearly 

 so numerous as the large. The wing plate (lamella) is also thickly 

 covered with hairs (pi. 41?, figs. 12-14). These are curved. The 

 direction of their curvature is determined by the direction of the 

 nearest longitudinal vein or fold. The hairs are inclined toward the 

 wing margin, in the same direction as that taken by the nearest 

 veins. Upon the anal portion, which comprises about two-thirds of 

 the entire wing, the hairs are inclined outward and backward toward 

 the posterior wing margin. To each hair of the upper side there is 

 a corresponding hair on the lower side, the places of insertion of 

 the dorsal and ventral hairs lying nearly opposite. It should be 

 noted that the photographs of the sections do not give a reliable 

 representation of the direction of the hairs, as the pressure of the 

 cover-glass in thin sections generally changes their position more 

 or less. 



THE FLEXIBLE ZONE 



(PI. 6, figs. 18, 19, si; pi. 7, figs. 20, 21, 22.) 



The anterior marginal vein is incised anteriorly by a conspicu- 

 ous notch (pi. 6, figs. t8, 19, si). This is situated just above the 

 anterior transverse vein. Closer examination with higher powers 

 shows that this notch is in truth a transparent, only slightly chitin- 

 ized and hairless part of the vein. In order to ascertain its sig- 

 nificance I grasped the base of a fresh wing with the forceps and 

 then' bent the tip backward with a needle. Even with the unaided 

 eye I could see that the wing was then always abruptly bent at the 

 same place, and that this flexible point lies about one-sixth of the 

 length of the wing distant from its base. On repeating this experi- 

 ment under the binocular I found that the bending always occurred 

 in a slightly curved zone beginning at the notch in the anterior 

 marginal vein. I call this bending zone the flexible zone (pi. 6, fig. 

 18). It extends from the before-mentioned notch backward over 

 the Ilba, which there shows a bowl-like depression, parallel to the 

 line formed by the anterior transverse vein and the knee of the 

 wing. Just within (proximally from) this zone the strong re- 



