JOURNAL OP AGMCOLTCRAL RESEARCH 
Vol. XXVIII Washington, D. C., April 5, 1924 No. 1 
ANATOMY AND METAMORPHOSIS OF THE APPLE 
MAGGOT, RHAGOLETIS POMONELLA WALSH 1 
By R. E. Snodgrass 
Deciduous Fruit Insect InvestigationSy Bureau of Entomology , United States Depart¬ 
ment of Agriculture 
INTRODUCTION 
Since all things of the present are products of the past, we can understand 
nothing rightly without knowing its history. This applies even to insects. 
But, among insects, so many species are so much alike that it is not necessary 
to know all phases of each one separately; the story of one may be repeated in 
the history of many others. Thus, the study of the apple maggot, here pre¬ 
sented, explains a type of development and structure common to a large group 
of flies that includes the various other fruit-flies, the root-maggots, the house 
fly, the blow-fly, the sheep tick, and all the host of forms related to these species, 
embracing most of the important fly pests of man, domestic animals, and culti¬ 
vated plants, as well as many beneficial species that are parasites of other insects. 
The larval form of these flies is called a maggot, but the maggot has had the 
strangest history of all insects, and an obscure one, too, for it is known only 
to a few entomologists. Yet, because of the economic importance of maggots, 
much has been written about them and, unfortunately, many of the published 
descriptions are vague or inaccurate because the writers did not understand the 
history of their subjects. 
The apple maggot, the larva of Rhagoletis pomonella Walsh, is an insect highly 
favored by nature. It lives among a superabundance of food, it grows to 
maturity in almost complete security from enemies, and is never exposed to 
the chance of being poisoned by the sprays of the orchardist. Its mother is a 
small fly (fig. 1, A) with a sharp drill at the end of her body by means of which 
she pierces the skin of the apple (fig. 1, B) and deposits her egg in the flesh be¬ 
neath. The young maggot, hatching from the egg, has only to burrow into the 
fruit (fig. 1, C), for here it spends its days tunnelling about and feeding on the 
pulp (fig. 2) until it is full grown. 
EXTERNAL STRUCTURE 
In general appearance the apple maggot is a smooth, white, wormlike creature, 
7 or 8 mm. in length when full-grown, having the external form and struc¬ 
ture shown in Plate 1, A. Its body consists of eleven distinct segments 
and a small, retractile, conical end-piece in front (LH)y which serves as a head 
and carries the pair of mouth hooks ( Hk ). The first body segment (I) bears 
the anterior larval spiracles (ASp) and the last segment (VIII) carries the poste¬ 
rior spiracles (PSp) and the anus (An). 
1 Received for publication February 21, 1924. 
Journal of Agricultural Research, XXVIII, No. 1 
Washington, D. C. April 5,1924 
Key No. K-126 
88285—24f-1 
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