MEXICAN" BEAN BEETLE IN THE SOUTHEAST. 5 



NATURAL SPREAD. 



The Mexican bean beetle is capable of long flights. In the western 

 part of the United States it must necessarily fly long distances to 

 suitable hibernation quarters. In its newer habitat in the Southeast 

 it migrates throughout the season, but especially in spring and fall. 

 Experiments with marked beetles show that a flight of 5 miles is 

 possible within two days and flights up to 3| miles are common. 

 Records of the spread in the Southeast indicate that much greater 

 distances than these are traversed with ease. 



Many other natural factors, of course, may contribute to the re- 

 markable spread of the beetle, among them being air currents and 



Fig. 5. — Map showing known distribution and spread of the Mexican bean beetle in the Southeast to 

 December, 1922. The map was prepared from records obtained through the cooperation of State ento- 

 mologists and others in the States concerned and chiefly from scouting done by the Bureau of Ento- 

 mology under the direction of J. E. Graf and the senior author. 



flood waters. It is believed, however, that the spread northward is 

 attributable to the fact that the Mexican bean beetle is a northern 

 Transition or sub-Boreal form, or at least is searching for conditions 

 similar to those found in the higher altitudes of the Southwest and 

 the Mexican plateau. No appreciable spread to the south in Ala- 

 bama or south from Thomasville, Ga., nor any spread west into 

 Mississippi, occurred during 1922. The damage to the bean crop in 

 many instances has been extremely severe the second year after the 

 insect has reached a new district of approximately the same latitude 

 as Birmingham, Ala., or farther north. No reports of persistent, 

 severe injury have come from southern points. Great damage oc- 

 curred at Chattanooga, Tenn., and Atlanta, Ga., in 1922, one year, 

 after the beetle was known to have reached these places. 



