3G4 
PLATE 2 
Rhagoletis pomonella 
A. —Dorsal view of right pronotal spiracle of pupa, showing passageway 
from base of stigmatic chamber to cuticle through which larval tracheal intima 
was shed attached to larval spiracle. 
B. —Posterior spiracles of second-instar larva. 
C. —Posterior spiracles of third-instar larva. 
D. —Posterior spiracles of first-instar larva. 
E. —Stigmatic plate at end of one lobe of stigmatic chamber of third-instar 
larva. 
F. —Dorsal tracheal trunk and lateral branches of last four segments of pre- 
pupal larva, showing lateral spiracles connected with lateral commissures, which 
will constitute the lower lateral longitudinal trunk of the adult tracheal system. 
G. —Principal trunks and branches of left half of larval tracheal system, third 
:instar. 
EXPLANATION OP SYMBOLS 
ASp, anterior larval spiracle. 
LH , larval head, external remnant of the in vagina ted true head. 
m , outer stigmatic scar, or closed outer end of passage through which tracheal 
^cuticle of preceding stage was shed with cast-off spiracle. 
n, inner stigmatic scar, in base of stigmatic chamber. (See ra.) 
PSp , posterior larval spiracle. 
PuSp, pupal dorsal spiracle of pronotum. 
q , anterior dorsal tracheal commissure. 
r, V-shaped dorsal tracheal commissures. (Only left halves shown.) 
s, posterior dorsal tracheal commissure. 
sp, spy lateral spiracles, the adult system, connected with lower longitudinal 
tracheal trunks. 
SpCy stigmatic chamber. 
SpPl , stigmatic plate. 
t , t, tracheal commissures forming lower lateral longitudinal trunks of adult. 
Tray dorsal longitudinal tracheal trunk. 
v , remains of passage from stigmatic chamber to body wall, through which 
tracheal intima of last stage was shed! (See m and ft.) 
