Apr. 5,1924 
Anatomy of the Apple Maggot . 
19 
nikov (23), Berlese ( 4, 5), Terre (45), Anglas (1), and P6rez (38, 39). The 
writer, in studying the metamorphosis of the fat body of the honeybee, found no 
evidence of phagocytosis, but was convinced that most of the fat cells do dis¬ 
integrate, as described by Bishop (8), after a normal dissolution of their mem¬ 
branes. He finds also no suggestion of phagocytosis of the fat body in the apple 
maggot, but in all cases a disintegration of large numbers of the cells, and this in 
the blood of fresh specimens removed with utmost care from the puparial shell. 
The origin of the fat body of the imago is difficult to determine in Diptera and 
Hymenoptera, but it appears most probable that it is formed from persisting 
larval cells, as Bishop (8) concludes in his study of the honeybee. Kreuscher (26) 
says that in Dytiscus the greater part of the larval fat body appears to go over 
without change into the adult, for the newly emerged beetle often has a fat body 
with cells rich in fat and full of albuminoid granules, in large part resembling the 
fat body of the mature larva. 
However, by whatever means the larval fat cells finally give up their contents, 
and whatever may be their ultimate fate, it is evident that they play very im- „ 
portant rdles in the metamorphosis of the insect, first, in the capacity of pre¬ 
parers of foodstuffs in the larva and of carriers of the same from larva to pupa, 
and, second, in that of elaborators of these reserves into food materials for the 
growing tissues of the adult. In the first case they use the pabulum absorbed 
from the alimentary canal of the larva; in the second they use the fatty reserves 
stored in them, perhaps also taking other materials from the blood, formed 
from the histolysis of the larval organs, and possibly also consuming some of their 
own protoplasm. 
THE MUSCLES OF THE BODY WALL 
Since the maggot has no legs to direct its motions, it must accomplish all its 
actions by movements of its body, but, so well developed to this end are the 
muscles of its body wall, that no act of shortening or lengthening, no contor¬ 
tionists twist or turn, is impossible to it. 
Plate 4, C, shows the inner walls of the first four body segments of the maggot 
cut open from above and spread out flat, with the pharynx turned forward, expos¬ 
ing its ventral surface. Plate 4, E, shows the right half and all of the back of two 
succeeding segments in the same position but somewhat more enlarged. It will be 
seen that all the muscles of the body wall lie flat against the skin and that most 
of them form an intricate network of fibers crossing in all directions. Two latero- 
ventral bands (VMcl) are the only longitudinal muscles of the body. In the first 
three segments these bands are augmented by extra muscles on each side, which 
become oblique in the fourth segment. 
In general, all the longitudinal and oblique muscles are attached at each inter- 
segmental line. In the thorax, however, the longitudinals are continuous from 
the edge of the first abdominal segment (PI. 4, C, 7) to their insertions on the rear 
margins of the larval head. These muscles are thus made particularly effective as 
retractors of the head and pharynx. In addition, all of one set of oblique muscles 
of the second segment are continued through the first to be inserted in a circle 
around the base of the head and on the roof of the atrium. By the combined 
action of all of these muscles the head can be entirely withdrawn into the prothorax 
and the latter itself greatly retracted (PL 4, D). The lengthening of the body 
is accomplished by the constrictive action of the oblique muscles and the resulting 
pressure of the blood and viscera. The oblique muscles cross one another in two 
regular systems as shown in Plate 4, C and E, forming a pattern repeated in each 
segment except the first, where one system is omitted. No muscles, however, 
cross the back, where the heart lies along the midline (PI. 4, E, Ht) in an open 
space between the muscles on opposite sides. 
