ANATOMY AND PHYSIOLOGY 63 



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 char- 

 acteristic odors of male butterflies have long been attributed to these 

 androconia, and M. B. Thomas has found that the scales arise from glan- 



B 



FIG. 96. Development of butterfly scales. 

 A. Vanessa; B, Anosia. b, basement mem- 

 brane; /, formative cell; h, hypodermis; s, 

 scale. After MAYER. 



FIG. 97. Androconia of butterflies. 

 Pier is ra$a; B, Everes corny ntas. 



dular cells, which doubtless secrete a fluid that emanates from the scale 

 as an odorous vapor, 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 function have 

 been found in insects. Most of these, being formed from the hypoder- 

 mis, may logically be considered here, excepting some which are inti- 

 mately concerned with digestion or reproduction. 



