INSECTS. 
Fic. 157.—Tongue of blow-fly. 
(Fig. 156) about fourteen days. 
The proboscis of the fly (Fig. 
157) is a fleshy, tongue-like 
organ bent under the head 
when at rest. In flying, the 
wings describe a figure 8 in 
the air, making 19,800 revolu- 
tions in a minute, or 9,400 
simple oscillations. The eyes 
(Fig. 158) are both compound 
and simple. The feet (Fig. 
111) have delicate pads for 
clinging upon smooth surfaces. 
Fleas (Pulicide).— The 
fleas (Fig. 160) are wingless, 
have a compressed body, and 
127 
Fic. 158.—Showing 
compound and sim- 
ple eyes of fly. 
A, head, enlarged 
8 times: c¢, com- 
pound eye; s, sim- 
ple eyes. JZ, por- 
tion of the surface 
of acompoundeye, 
highly magnified. 
FIG, 159.—Spiracle of a fly. 
