ANATOMY AND PHYSIOLOGY 79 
Uses of Scales.— Among Thysanura and Collembola, scales 
occur only on such species as live in comparatively dry situa- 
tions, from which it may be inferred that the scales serve to 
retard the evaporation of moisture through the delicate integu- 
ment of these insects. This inference is supported by the fact 
Fic. 96. Fic. 97. 
Development of butterfly scales. Androconia of butter- 
A, Vanessa; B, Anosia. b, base- flies. A, Pieris rape; B, 
ment membrane; f, formative cell; Everes comyntas. 
h, hypodermis; s, scale.—After 
MAYER. 
that none of the scaleless Collembola can live long in a dry 
atmosphere; they soon shrivel and die even under conditions 
of dryness which the scaled species are able to withstand. In 
Lepidoptera the scales are possibly of some value as a mechan- 
ical protection; they have no influence upon flight, as Mayer 
has proved, and appear to be useful chiefly as a basis for the 
