BUREAU OF ENTOMOLOGY. 239 



1917, in South Carolina, Georgia, and Alabama. The caterpillars 

 first attacked fields of hairy vetch and then, after completely strip- 

 ping this crop, migrated to cotton. A remarkable phenomenon ob- 

 served in this connection was the unusual color and variability of 

 the markings of the tubercles in the caterpillars. So markedly 

 changed was their appearance as to deceive experienced entomologists 

 and lead them to suppose that an unknown pest had appeared. The 

 earworm has proved amenable to the usual remedies. 



Eange caterpullar. — During the summer of 1916 the range cater- 

 pillar appeared to have decreased so greatly in numbers that it was 

 deemed advisable to reduce considerably, for the time being, the 

 force of investigators detailed to this project. The cause of this 

 decrease is somewhat obscure, but it may be due to the work of the 

 natural enemies that have been introduced artificially in great num- 

 bers and become established in portions of the area infested. A 

 survey is being made during the summer months of 1917 to deter- 

 mine the future necessities of the investigation. 



Insects affecting the production of clo\t:r seed. — An extensive 

 investigation of the insects affecting clover-seed production is in 

 progress in the Pacific States. The clover-flower midge in the Pacific 

 Northwest has proved amenable to the same methods of control that 

 have been recommended and used in the Eastern States for many 

 years, and the clover growers in the Northwest are adopting the 

 methods recommended by the experts in charge of State and Federal 

 stations. 



The clover root-borer, which is numerous in Oregon and AVash- 

 ington, has been made the subject of a special investigation to deter- 

 mine its powers of flight, as affecting its distribution. Further 

 progress has been made in the control of the clover-seed chalcis. 



Emergency work. — In order to meet the emergency caused by the 

 war and the diminution in cereal crops throughout the United States 

 several special publications giving specific advice, most of them in the 

 form of posters or post cards mailed directly to the growers most 

 interested in the various cereal crops, have been prepared and widely 

 distributed. A Farmers' Bulletin (No. 835) has been published sum- 

 marizing briefly the methods necessary for the detection, elimination, 

 and control of the principal insects, such as the Hessian fly, chinch 

 bug, army worm, cutworms, grasshoppers, white grubs, billbugs, 

 wireworms, and the corn root-aphis, which affect cereal crops. 



INVESTIGATIONS OF INSECTS AFFECTING FOREST AND SHADE 

 TREES, FOREST PRODUCTS, AND HARDY SHRUBS. 



The branch of Forest Insect Investigations has continued under 

 the supervision of Dr. A. D. Hopkins and has been conducted with 

 special reference to the working out of the seasonal histories of the 

 insects and to the determination of the effect of climatic conditions 

 on their distribution and periodical activities, and the principles 

 underlying prcA^ention and control of their outbreaks and injuries. 



