6 DEPARTMENT OF AGRICULTURE BULS. 826-850. 



Department Bulletin No. 838. — Cypress Bark Scale— Continued. page. 



Injury 4 



Associated insects 7 



Food plants 8 



Description -. 8 



Life history and habits 12 



Seasonal history 16 



Predaceous and parasitic enemies 18 



Control experiments 19 



Recommendations for control 20 



Summary 22 



Department Bulletin No. 839. — The Microscopical Examination of 

 Flour: 



Review of literature 1 



Purpose of investigation 3 



Microscopical method 3 



Sources of variation in method 5 



Examination of mill stocks 11 



Examination of commercial grades of flour 16 



Examination of experimental series of flour 29 



Summary 31 



Bibliography 32 



Department Bulletin No. 840. — A System of Records for Local Farmers' 

 Mutual Fire Insurance Companies: 



Introduction 1 



Systems now in use 2 



System recommended 2 



Policy register 3 



Increases and cancellations 8 



Cash receipts and disbursements 8 



Annual report 9 



Index of policyholders 15 



Periodic summaries 16 



Conclusions 22 



Publications relating to farmers' mutual fire insurance companies 23 



Department Bulletin No. 841. — The Western Grass-stem Sawfly: 



Introduction 1 



History 2 



Food plants 8 



The egg 9 



Development of the egg 10 



The larva 11 



The pupa 16 



The adult 17 



Oviposition 19 



Key to North American species of Cephus 22 



Natural control 23 



Artificial control 24 



Cephus pygmaeus (L) 26 



Description 27 



Department Bulletin No. 842. — The Nematode Disease of Wheat Caused 

 by Tylenchus Tritici: 



Occurrence of the disease 1 



History 2 



Distribution 4 



Economic importance 6 



Description of the disease 6 



Differences between this disease and tulip-root 8 



Origin and description of the galls 9 



Cause of the disease 10 



Effect of high temperatures on the larvae 19 



Effect of chemicals on the larvae 24 



Overwintering of the parasites 27 



