=Spinules, hair-scales, hair-fields, and androconia.=—Besides the scales, fine spinules occur on the thickened veins of the wings of the Blattidæ, where they resemble fir-cones; also in the Perlidæ, in the Trichoptera, and in the more generalized Lepidoptera (Micropterygidæ and Hepialidæ), occur, as indicated by Spuler, delicate chitinous hollow spinules scarcely one-tenth as long as, and more numerous than, the scales, which sometimes form what he calls “Haftfelds,” or holding areas. These spinules have also been noticed by Kellogg, and by myself in Micropteryx; Kellogg, and also Spuler, have observed them in certain Trichoptera (Hydropsyche). These also occur on the veins, and detached ones near large one-jointed hairs, or hair-scales, said by Kellogg to be striated. Kellogg has detected these scale-hairs, as he calls them, in Panorpa. [Illustration: FIG. 227.—View looking down upon the upper (_i.e._ exposed) surface of one of the large scales situated on the veins of _Danais plexippus_, about four days before emergence: _clm_, chitinous pillars found in scales. _A_, _a_ smaller scale, _a_, _a′_, sections of the scales. _B_, leucocyte found in the larger scale.—After Mayer. ] [Illustration: FIG. 228.—Scale-follicles: _A_, of a scale of _Galleria mellonella_: _r_, neck-ring. _B_, the same of _Polyommatus phlæas_. _C_, the same of a hair on inner edge of hind wing of _Lycæna alexis_ ♀.—After Spuler. ] [Illustration: FIG. 229.—_A_, portion of wing of a caddis-fly (Mystacides). _B_, enlarged, showing the androconia and hair-scales. _C_, a separate androconium.—After Kellogg. ] The “hair-scales” of the phylogenetically older Trichoptera correspond to certain scales of Lepidoptera, especially the Psychidæ (Spuler), variously called “plumules” (Deschamps), “battledore scales,” also certain minute cylindrical hairs. To these scent-scales is applied the term _androconia_. They are found, almost without exception, on the upper side of the fore wings, occurring in limited areas, such as the discal spots, or on folds of the wings. Fritz Müller has shown that they function as scent-scales, and are confined to the males. Kellogg has detected androconia-like scales on the wings of a caddis-fly, _Mystacides punctata_ (Fig. 229). [Illustration: FIG. 280.—Cross-section of androconia surface on wing of _Thecla calanus_; _a_, androconia; _gl_, gland of base; _s_, ordinary scales; _w_, wing in section.—After Thomas. ]