Beck, on the Scales of Lepidocyrtus. 83 
" Scales of Insects/^ " The interesting markings seen upon 
the scales vary considerably in different insects. The most 
common, as seen by transmitted light, are longitudinal, 
simple, continuous, parallel, or slightly radiating dark strise 
or lines These longitudinal strise consist of 
elevations or ridges upon the surface, probably representing 
folds of the upper layer or membrane of the scale. They 
often project slightly from the free end of the scale, and, 
when moistened, bubbles of air may not unfrequently be found 
imprisoned between the surface of the scale and the cover, 
which, being confined between two of the ridges, assume an 
oblong form. ......... 
" In the scales of Podura the strise consist of longitudinal 
roAvs of minute wedge-shaped bodies. . . . . . 
The darkness of the longitudinal strise is caused by re- 
fraction ; for scales containing no pigment appear perfectly 
white by reflected light, although the strise may be very 
dark. .......... 
^' Upon certain scales other irregular, more or less trans- 
verse curved strise exist ; these appear to consist of wrinklings 
or folds of the under membrane of the scale. 
When the insects are pressed against the slide to remove 
the scales, a number of globules of oil adhere simultaneously 
to the slide ; and when the cover is applied, the scales often 
become partially or entirely covered with the oily matter, 
producing an appearance as if the upper layer of the scale 
were removed, and rendering the markings so pale and indis- 
tinct, as to be apparently absent.^'' 
The remark that the strise on the Podura-scales consist 
of longitudinal rows of minute wedge-shaped bodies, conveys 
the idea that each marking is isolated, and the illustration, 
besides confirming this error, shows neither the blackness nor 
the light spaces of the markings, and the absence of these 
two essential points are proofs of inferior definition. The 
other points noticed in the extract are entirely confirmed by 
my own observations. I believe, when no pigment is present in 
the scales, not only that the darkness of the longitudinal strise, 
but that all the markings on the scales are entirely due to the 
refraction or to the reflection of the light. In the ordinary 
course of things, the naked eye is totally unaccustomed to the 
the examination of transparent objects by light transmitted 
through them ; but in using the microscope, this is the com- 
mon mode of procedure. No little care is required in obser- 
vation to discover the true structure under such circumstances, 
for the presence or the absence of matter may produce the 
p.arae appearance. 
