UNITED STATES DEPARTMENT OF AGRICULTURE 



jr^r^?U"t. 



Contribution from the Bureau of Entomology 

 L. O. HOWARD, Chief 



Washington, D. C. 



V 



November 4, 1921 



WALNUT HUSK-MAGGOT, 1 



By Feed E. Brooks, Entomologist, Fruit Insect Investigations. 



Introduction 



Brief description of insect and in- 

 jury _ 



Synonymy 



Distribution 



Food plants 



CONTENTS. 



Page. 

 1 



Description of life stages _.. 



Activities of the flies 



Nature of injury 



Natural enemies 



2 Methods of control. 

 3 



Page. 



INTRODUCTION. 



The larva of the walnut husk-maggot has long been known to 

 persons who in autumn have engaged in hulling the nuts of our 

 native black walnut (Juglams 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 (PI. 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 Rhdgoletis suavis Loew : order Diptera, family Trypetidae. A closely allied species, 

 Rhagoletis juglandis Cresson, has been recorded as attacking the nuts of Juglans rupestris 

 and J. 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 Walsh, 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. cingulatu 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 



