186 NORTH AMERICAN INSECTS. 
this dust has regular forms, and consists of horny scales, 
fastened in the wings. From this circumstance the order 
of entomology comprising Moths and Butterflies is called 
Lepidoptera, which signifies in English “ Scale-winged.” 
The head of these insects is provided with two large glob- 
ular eyes, covered with a horny skin, which under the mag- 
nifying glass looks like a net-work, consisting of a number 
of elevated points or convexities, of which each one may, 
perhaps, be considered a single eye. This horny skin is 
transparent, and when taken off and looked through, for 
instance, at one man, there are presented to us a whole 
army of Liliputians. But in spite of this multifarious vi- 
sion, the insect probably sees only that object which is in the 
direct angle of vision, or which is in a straight line with its 
point of sight. 
Figure 28. 

Saturnia Io.—Female. 
On the upper part of the head, between the eyes, are 
seen two thread-like filaments, called “ feelers,’ antenne, 
as in the Saturnia Jo (Figs. 27 and 28), and in the Asterias 
(Fig. 30). The use of these organs has not yet been exactly 
