14 



BULLETIN 1243, U. S. DEPARTMENT OF AGRICULTURE. 



At least as early as the first week in October the beetles begin to 

 fly to woodlands and enter hibernation. The majority have left the 

 fields by the time the daily mean temperatures reach 55° to 60° F., 

 but a few remain until heavy frosts occur. 



Fewer eggs are laid after the middle of August. Larva? are cor- 

 respondingly scarce, but all stages are present until killing frosts 

 occur. 



Life for long periods without food, as shown by starvation tests, 

 indicates that the species is remarkably prepared for adverse con- 

 ditions when host plants may be unavailable. One adult lived 102 

 days without food in the presence of moisture. In general they 









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Fig. 9. — A typical infested bean plant photographed in the field shown in Plate VI, B. 



succumb to starvation after 5 to 15 days, but a few live considerably 

 longer. After starving for 68 days, 19 beetles out of 50 survived and 

 entered hibernation November 22, 1922. An adult with food lived 

 121 days. The average life of 34 pairs used in experiments was 58 

 days, the females averaging 50 days and the males 68. 



FOOD PLANTS. 



The Mexican bean beetle is primarily a bean pest (PL VI, A, B; 

 text fig. 9), attacking by preference the common beans, including 

 bush and pole varieties of snap beans, pinto, navy, and Lima beans, 

 and tepary beans, all of the genus Phaseolus. It can subsist, however, 

 on a number of other plants, and in many instances has severely 

 damaged cowpeas and soy beans. About Birmingham, Ala., in 1921, 

 and about Chattanooga, Term., in 1922, some fields of cowpeas were 



