Apr. 5, 1924 
Anatomy of the Apple Maggot 
21 
THE NERVOUS SYSTEM 
The nervous system of the maggot is highly specialized by the condensation 
of the ventral ganglia. The brain consists of two lobes (PI. 3, F, Br) embracing 
the oesophagus and connected by a thin bridge above it. There is but one 
ventral nerve mass, a long, compound ganglion (Gng) which is suspended in the 
body cavity, and extends from the brain to beneath the anterior end of the 
stomach. This ganglion shows no superficial evidence of its composite origin, 
except in the numerous paired nerve trunks that arise from it. Only the larger 
ones of these are shown in the figure. 
The unusual position of the brain, in the back part of the thorax (PL 3, F, Br), 
is evidently due to the invagination of the primitive head. Since it lies imme¬ 
diately behind the frontal sacs ( FS ) and gives off a short nerve to each optic bud 
(ob), its position is normal in relation to these parts. In the embryo, as shown by 
Pratt (41) j the brain lies in the head behind the frontal involutions. The sus¬ 
pension of the ventral ganglion (Gng) appears to be for the purpose of allowing 
its free motion back and forth with the extension and retraction of the pharynx 
and the forward parts of the body wall. 
METAMORPHOSIS 
The apple maggot attains its full growth in the fruit where it reaches larval 
maturity by the end of summer. By this time, however, the decay of the pulp, 
spreading from the maggot's excavations, has caused the apple in most cases to 
drop to the ground. The mature maggot tunnels outward in the fruit, makes a 
small exit hole in the skin, emerges, and enters the earth to a depth of from 1 
to 3 inches. 
Scarcely, however, has the maggot given itself proper burial when its skin 
begins to turn yellow, to shrink, and to harden. These changes progress till the 
creature loses all power of movement and has become transformed, by the end of 
12 hours, into a motionless, hard-shelled, seedlike object, brown in color, and 
only 4 or 5 millimeters long, or about two-thirds the length of the active maggot. 
The insect in this state is usually called a puparium (PI. 5, A, B), but the term, 
should be used to designate only the hardened larval skin which now forms a 
tough capsule within which the insect will complete its larval life, go through its 
pupal stage, and transform to the fly. The puparium is, therefore, not a “stage” 
of the insect's life history. The short length of the puparium as compared with 
that of the active maggot is due not only to the shrinking of the cuticle, but also 
to a final involution of the anterior parts, which results in the complete disappear¬ 
ance of the larval head, and in the infolding of nearly all of the prothoracic 
segment. As a consequence the anterior larval spiracles (A/Sp) come to project 
from the anterior lateral angles of the puparium. 
The external surface of the puparium retains the larval characters, though 
some of them in modified forms. The segmentation is still evident and the inter- 
segmental lines are marked by the bands of hooklets, but the swellings have dis¬ 
appeared and the contour is unbroken. Both pairs of larval spiracles are present 
(PI. 5, A, ASp , PSp), but the papillae about the area of the posterior spiracles 
are much reduced in size, the smaller ones being scarcely perceptible. The larval 
mouth is now closed by the hardening of the indrawn parts which form a chitinous 
plug (Mth) in front of the atrium. The anal lobes (An) have become densely 
chitinized and closely appressed, but not fused. 
On the other hand certain new characters have developed. During the 
transformation a ridge swells out on each side of the anterior segments on which 
there appears a seamlike line (6) continuous from one side to the other around 
the front of the pro thorax just below the anterior spiracles. This line ends 
