2 BULLETIN 1103, U. S. DEPARTMENT OF AGRICULTURE. 



The data upon which these summaries are based were collected 

 during the growing season by collaborators, including the field work- 

 ers of the Bureau of Entomology. Where the review of an insect was 

 drawn largely from the general files of collaborators' reports, no 

 special credit is given in the annual summary. Where the review 

 was drawn from the reports of one or a few workers, acknowledge- 

 ment is made in footnotes. 



Weather data were tabulated, graphically presented, and correlated 

 with the various insect outbreaks by the survey. In these studies an 

 arbitrary year has been adopted, starting with September and run- 

 ]iing through to September of the succeeding year, instead of using 

 the calendar or fiscal year. Insect outbreaks are undoubtedly pre- 

 determined to some extent by the conditions prevailing during the 

 late fall and early winter of the year preceding the actual outbreak 

 and culminate before the end of the calendar year in which the out- 

 break occurs. The fiscal year ending June 30 is obviously not 

 adaptable to studies relating to insect activity. 



In the discussion of insect outbreaks and associated meteorological 

 conditions, it is often convenient to refer to a region rather than to 

 a political unit. For convenience, we have adopted an arbitrary 

 division of the United States into 12 regions. New England in- 

 cludes the States usually recognized under this name; the Middle 

 Atlantic States include the Atlantic Coast States from New York 

 to Virginia, inclusive, and also West Virginia and Pennsylvania ; the 

 South Atlantic States embrace the remainder of the Atlantic Coast 

 States, including Florida. These three groups range from sea level 

 to 1,500 feet in elevation, a few isolated mountain ranges running 

 above this elevation, and a large part of the territory is in the 

 Coastal and Piedmont regions. 



The North-Central States include the two Dakotas, Minnesota,, 

 and Wisconsin, the entire region ranging from 500 to 1,500 feet 

 elevation; the East-Central region takes in the States in the Ohio 

 River Valley, including Illinois, Indiana, Ohio, Kentucky, and also 

 Michigan; the West-Central States include the corresponding terri- 

 tory west of the Mississippi River — Iowa, Missouri, Nebraska, and 

 Kansas; the lower Mississippi Valley includes all of the States bor- 

 dering on the Gulf of Mexico, with the exception of Florida, and 

 also includes Oklahoma, Arkansas, and Tennessee. The Central and 

 Mississippi Valley States are all practically below the 3,000-foot 

 elevation line. The lower Mississippi Valley States and South At- 

 lantic States cover practicallj^ the cotton belt. 



The Rocky Mountain States are Montana, Wj^oming, and Colo- 

 rado. With the exception of a small territory in northeastern Mon- 

 tana, these States are all above the 3,000-foot elevation line. The 



