UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 992 
Contribution from the Bureau of Entomology 
L. O. HOWARD, Chief 
S&r^j-u 
Washington, D. C. 
November 4, 1921 
WALNUT HUSK-MAGGOT. 
By Fred E. Brooks, Entomologist, Fruit Insect Investigation, 
CONTENTS. 
Page. 
Introduction 
Brief description of insect and in- 
jury 
Synonymy 
Distribution 
Food plants 
Description of life stages 
Activities of the flies 
Nature of injury 
Natural enemies 
Methods of control 
Page. 
4 
6 
INTRODUCTION. 
The larva of the walnut husk-maggot has long been known to 
persons w T ho in autumn have engaged in hulling the nuts of our 
native black walnut (Juglans nigra). Soon after the nuts drop, a 
large percentage of them are frequently found with the hulls black- 
ened and slimy within and containing multitudes of whitish mag- 
gots which move actively through the soft pulp. Such infested nuts 
are disagreeable to handle, and in hulling the husk sticks to the 
inner shell, leaving it dirty and unattractive in appearance (PL IV. 
d). Inasmuch as the fruit of the black walnut was not important 
commercially in the past this insect did not attract especial attention, 
and very few persons, even of those who were familiar with the mag- 
gots in the walnuts, ever saw the parent fly. If seen, it was probably 
seldom regarded as being in any way connected with the disgusting 
1 Rhagoletis suavis Loew ; order Diptera, family Trypetidae. A closely allied species,. 
fthagoletis juglandis Cresson, has been. recorded as attacking tbe nuts of Juglans rupestris 
and •/. regia in Arizona and Texas. Several members of the same genus have attracted 
considerable attention in North America on account of the destructiveness of the larvae 
to various kinds of fruit. R. pomonella W T alsh, known commonly as the apple maggot 
or railroad worm, is an important pest of apples in the northern part of the United' 
States and Canada. Two species, R. cinguUita Loew and R. fausta- O. S., attack cherries 
over practically the same region, while R. ribicola Doane frequently injures currants and 
gooseberries in the Northwestern States. 
55813°— 21 
