Apr. 5,1924 
Anatomy of the Apple Maggot 
23 
The larva of Rhagoletis remains in this post-puparial instar a varying length 
of time, but usually not beyond the end of 48 hours from the time it entered the 
ground. Then begins another molt which ends in the complete shedding of the 
papillated cuticle and in the disclosure of the true pupa. But the cast-off integu¬ 
ment is not broken; it remains as a delicate, transparent pellicle about the pupa 
in all its phases of transformation. When the adult fly escapes from the pu- 
parium it leaves behind, within the puparial capsule, two ruptured skins, the 
cuticle of the prepupal larva and the cuticle of the pupa, the first characterized by 
its close-set papillation, the second by a fine surface striation. 
The membranous pupal envelope has been noted by other investigators. 
Kunkel d'Herculais (27) says of the Syrphidae: “The pupa is really enclosed in a 
very delicate skin, a true chitinous cuticle secreted by the hypoderm at the 
moment of metamorphosis to ensheath all the members. Within this envelope, 
so transparent that the development can easily be followed through it, the insect 
organizes itself into the adult. ” 
The shedding of the prepupal cuticle begins at the anterior end of the body 
(Pl. 5, D, E) ancf, as the leg buds and the wing buds are everted, the thorax 
shrinks, thus creating a considerable space inside the loosened membrane. From 
its first appearance the pupa suggests the structure of the fly with its large 
mesonotum (PI. 5, D, N 2 ) bordered in front by a narrow pronotum and behind by 
a rudimentary metanotum. The appendages, however, are small at this early 
period and there is yet no sign of the future head. By the shrinkage of the 
thorax in the transformation, the tracheal linings (PI. 5, E, tra ) attached to the 
anterior larval spiracles are partially drawn out of the body of the pupa. The 
new pupal spiracles ( PuSp ) appear between them on the anterior rim of the pro¬ 
notum (PI. 5, D, N 2 ). The pharyngeal skeleton of the larva, however, remains 
normally still within the pupa, but since it retains its connection with the pupa- 
rium, it is always extracted with the latter when the puparial shell is removed, 
leaving a rupture in the prepupa cuticle. For this reason the atrium (Atr) 
appears in Plate 5, E, as an empty, wide-open hole in the front of the thorax. 
The molt progresses backward over the abdomen till finally, at the end of the 
third day, it forms a complete bag (PI. 5, F, ppu) containing the pupa (Pu) 1 but 
still anchored to the latter by the linings of the tracheae, of the stomodeum, and 
of the proctodeum, and attached to the puparium (pm) at the spiracles, mouth, 
and anus. The abdomen has the prepupal form, but there are no posterior spir¬ 
acles replacing those of the larva as on the prothorax. There is still no head 
visible. This phase of the pupal development is the one described by Wahl (51) 
as the cryptocephalic sta^e. 
The pupa remains in this substage (PI. 5, F) for a variable period of time, and at 
first can be easily removed from the puparium in the headless form. But, a little 
later, the slightest pressure consequent on handling causes the head to pop out 
of the hole in the anterior end of the thorax, when the pupa suddenly assumes the 
grotesque aspect shown in Plate 6, A. The head is so easily forced out at this 
period that it can not be demonstrated that its eversion at this time is a normal 
phase of development, but the appearance of the head marks the beginning of the 
second substage of the pupa, the one called by Wahl (51) the phanerocephalic 
stage, which in its final phase is shown in Plate 6, C and D. 
When the head is first exposed it is very small (PI. 6, A) as compared with its 
eventual size (PI. 6, D). It is a tense, thin-walled capsule with the ptilinum 
everted in the form of a caplike lobe (Pt) on the anterior dorsal aspect. Just 
below the ptilinum is a transverse, bilobed ridge (Ant) within which are developed 
the antennae of the fly. On the sides of the head are the compound eyes (E), 
very small at this period, and below each of them a swelling (u) which is more 
developed in the next phase (PL. 6 C, D), but which is lost in the adult. The 
