22 
Journal of Agricultural Research 
Vol. XXVIII, No 1 
posteriorly on each side near the middle of the fourth segment, where it meets a 
second transverse line (p) encircling this segment. These seams are the lines of 
cleavage along which the puparial shell will be broken open by*the escaping fly. 
Finally, as soon as the puparial cuticle is well chitinized, there appears along 
each side of the body a row of nine minute stigmata, the primitive lateral spi¬ 
racles ( Sp) which have remained rudimentary and invisible during the preceding 
larval period. The first is located on the methathorax just below the lateral 
ridge, the next is in the lower angle of the two cleavage lines that meet on the 
side of the first abdominal segment, and the others follow in line to the eleventh, 
or eighth abdominal, segment where the last of the series is situated just below 
the upper of the two lateral papillae at the sides of the area of the posterior 
spiracles. These stigmata represent all the adult spiracles except the first, which ? 
though it appears later on the pupa, is apparently obscured by the involution 
of the prothoracic parts of the puparium. 
Though the transformation to the puparium normally goes on beneath the 
ground, it will take place whether the larva is buried or not so long as it is in 
an atmosphere sufficiently moist. Hence, for convenience of study, maggots 
may be collected in a dish as they leave the apples, killed in hot water at desired 
intervals, and transferred to 85 per cent alcohol, where the puparial shell should 
be broken. The soft-bodied insect within the puparium can usually be quite 
, easily removed intact, when it is 24 hours old or over, by gently scratching the 
shell crosswise with a sharp needle till it splits. One end of the capsule can 
then be taken off and the insect removed from the other. 
During the first few hours after the completion of the puparium the hardened 
cuticle retains its connection with the hypoderm; but at the end of 4 hours in 
some specimens, later in others, the puparium becomes partly loosened from the 
inner skin, and after 12 hours it usually forms a free capsule that can be easily 
removed from the body of the insect within, though it still adheres to the latter 
at the mouth, anus, and spiracles. 
Now, from reading most descriptions of fly metamorphoses, we should expect 
to find a pupa within the puparium. But the object disclosed in the puparial 
capsule of the apple maggot at this stage has no character suggesting a pupa. 
There are no signs of legs or wings; the form is a mere replica of that of the 
puparium, though smaller in size; and the lateral spiracles are still closed. The 
new creature, moreover, has a cuticle distinctly its own, characterized, not by 
any of the former larval characters, but by a uniform, minute papillation all 
over its surface (PI. 5, C). Alcoholic specimens show a whitish film between 
the new cuticle and the loosened puparium, suggesting a coagulated molting 
fluid. In fact, it is evident that the maggot of the third instar has changed 
by a puparial molt (pm ), not to a pupa, but to a /owrM-instar larva—an intra- 
puparial, prepupal larval stage ( Ppu ) complete in all respects except for the 
retention of the stomodeal, proctodeal, and tracheal linings of the third larval 
instar. 
This intrapuparial larval stage of the fly has received scant notice from other 
writers, and its existence is not generally recognized. Lubbock (29 ), however, 
in describing the development of Lonchoptera 60 years ago, said: “When the 
larva is full grown it detaches itself from the skin, which retains its form, and 
within which the insect changes into a white, opaque grub, consisting apparently 
of 13 segments, which gradually diminish in size from one end to the other. 
There are no limb cases. The skin is covered by small papillae.” But De Mei- 
jere (31) would discredit Lubbock’s interpretation of what he saw, and suggests 
that the “grub” inside the puparial skin was the larva of a parasite. A rein¬ 
vestigation may prove that Lubbock was correct. 
