478 The House Fly. [ August, 
cause them to become dwarfed. It is evident that heat and 
moisture are required for the normal development of the fly, as 
they are for nearly all insects. ; 
The maggot molts twice, consequently there are three stages 
of development, and it becomes sensibly larger at each stage. 
After remaining in the first stage for one day it molts, and dif- 
fers from the preceding stage only in being a little larger, and in 
the addition of the spiracle near the head (Figure 28, B, sp. C, 
the same enlarged.) After reniaining in this stage from twenty- 
four to thirty-six hours it sheds its skin and enters upon the 
third stage, which lasts three or four days. Figure 28, A, B, 
represent the maggot; the body is long and slender, somewhat 
conical, the head and mouth-parts being rudimentary. The end 
of the body is truncated, and bears two short tubercles or spiracles. 
Figure 28, E, represents one of these circular breathing holes much 
enlarged, with three sinuous openings, the edges of which are 
i 2 A 
(Fic. 28.) EARLY STAGES OF THE HOUSE FLY. i 
armed with fine projections forming a rude sieve for the t A 
sion of dust and dirt. With these spiracles connect the da 
main tracheæ, communicating by two cross branches 0) fers 
sending off numerous twigs. The young of the Hotay i; 
chiefly from that of the flesh fly in being only one half as nae 
while the form of the openings in the spiracles at the end of ™ 
body is entirely different. state the 
When about to transform into the pupa or chrysalis sta ite : 
1 A, larva of Musca domestica, just hatched, showing the distribution oe P, 
main tracheæ, and the anterior and ior commissures (4, 4), dor of the sme 
the larya in the second stage; sp, spiracle. C, spiracle enlarged. Tibet E 
larva, enlarged ; bl, labrum (?); md, mandibles ; mx, maxillæ ; ft, prear 
minal spiracle much enlarged. D, puparium; sp, spiracle, All the "gna 
large. 
