SO ENTOMOLOGY 
development of color and color patterns—which are not infre- 
quently adaptive. 
Androconia.—The males of many butterflies, and the males 
only, have peculiarly shaped scales known as androcoma (Fig. 
97); these are commonly confined to the upper surfaces of the 
front wings, where they are mingled with the ordinary scales 
or else are disposed in special patches or under a fold of the 
costal margin of the wing 
Fig. 08. = a ; 
(Thanaos). The characteris- 
iN ly, tic oders of male butterflies 
& ; <we have long been attributed to 
= these androconia and M. B. 
Thomas has found that the 
NY 
scales arise from glandular 
cells, which doubtless secrete 
a fluid that emanates from 
the scale as an odorous va- 
—— 
por, the evaporation of the 
Bee ee ee ae eee fluid being facilitated by the 
Hylobius, to show bulbous glandular spreading or branching form 
cage a of the androconium. Similar 
scales occur also on the wings of various moths and some 
Trichoptera (Wystacides). 
Glands.—A great many glands of various form and func- 
tion have been found in insects. Most of these, being formed 
from the hypodermis, may logically be considered here, ex- 
cepting some which are intimately concerned with digestion 
or reproduction. 
Glandular Hairs and Spines.—The presence of adhesive 
hairs on the empodium of the foot of a fly enables the insect 
to walk on a smooth surface and to walk upside down; these 
tenent hairs emit a transparent sticky fluid through minute 
pore canals in their apices. The tenent hairs of Hylobius 
(lig. 98) are each supplied with a flask-shaped unicellular 
gland, the glutinous secretion of which issues from the bulbous 
