8o 



ENTOMOLOGY 



FIG. 98. 



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 androconia (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 

 ( Thanaos) . The characteris- 

 tic odors of male butterflies 

 have long been attributed to 

 these androconia and M. B. 

 Thomas has found that the 

 scales arise from glandular 

 cells, which doubtless secrete 

 a fluid that emanates from 

 the scale as an odorous va- 

 por, the evaporation of the 

 fluid being facilitated by the 

 spreading or branching form 

 of the androconium. Similar 

 scales occur also on the wings of various moths and some 

 Trichoptera (Mystacides) . 



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 Hylobhts 

 (Fig. 98) are each supplied with a flask-shaped unicellular 

 gland, the glutinous secretion of which issues from the bulbous 



Section across tarsus of a beetle, 

 Hylobius, to show bulbous glandular 

 hairs. After SIMMERMACHER. 



