﻿UNITED STATES DEPARTMENT OF AGRICULTURE 



DEPARTMENT BULLETIN No. 1393 



Washington, D. C. 



May, 1926 



THE GRANARY WEEVIL^ 



By E. A. Back, Entomologist in Charge, and R. T. Cotton, Associate Entomolo- 

 gist, Stored- Product Insect Investigations, Bureau of Entomology 



CONTENTS 



Page 



Introduction 1 



S3monymy 1 



Economic history 3 



Origin and distribution 5 



Nature of injury 7 



Technical description 9 



Life history and habits 14 



Parasites 29 



Control measures 29 



Summary 30 



Literature cited 32 



INTRODUCTION 



The granary weevil (Sitophilus granarius L.) (fig. 1) is well named, 

 for of all the primary grain pests it is par excellence a pest in the 

 ^anary or storehouse. Unlike its more successful and widespread 

 rival, the rice weevil (Sitophilus oryza L.), the granary weevil pos- 

 sesses only rudimentary wings and does not appear to thrive in 

 tropical and semitropical climates. Restricted as it is to the gran- 

 aries of the colder climates, it seems to be finding it increasmgly 

 difficult to withstand the combined effect of limited numbers of 

 generations due to cold and the modern methods of handling and 

 protecting grain. 



As late as the decade from 1860 to 1870 the granary weevil was 

 the prevailing species of weevil in grain throughout the northern 



Eartion of the United States. E. A. Schwarz, of the Bureau of 

 ntomology, states that Sitopliiluf! granarius was the only grain 

 weevil present among the insects (collected by C. V. Riley in Missouri 

 and later acquired by the United States National Museum. The 

 writers, who have examined many samples of grain from various 

 grain centers of this country, believe that the granary weevil is a 

 minor pest as compared with the rice weevil, and that it is responsible 

 for a relatively small amount of the damage caused by calandrid 

 pests in this country, notwithstanding the numerous instances of 

 serious injury that are constantly coming to one's attention. Keys 

 distinguishing the larvae and adults of granarius and oryza have 

 been givcsn by Cotton {13)? 



SYNONYMY 



The granary weevil was described and luuucd by Linne (44, y. 37S) 

 in 1758 as Curculio granarius. Numerous references to this weevil 



' 'J'he bioloKlcal data contained In this bulletin iiro based on work conducted In Florida from 1919 to 

 1021 and In WasliinKton, IJ. ('., from 1921 to 1923. 

 ' Ucferencc Is made by number (Italic) to "Literature cited," p. 32. 



7223»°— 2fi 1 



