MEXICAN BEAN BEETLE IN THE SOUTHEAST. 17 



from Colorado were planted with a legume collection on the experi- 

 mental plats. Careful counts showed that more than twice as many 

 adults were present on the pinto beans, and they were destroyed 

 sooner than a collection of six of the most popular varieties of garden 

 bush beans. In 1922 tepary beans were decidedly preferred to 11 

 varieties of the commonest pole and bush beans, although the leaves 

 were small and the insect was exposed to the sun. These facts 

 support the statement that the bean beetle was introduced from the 

 western part of the United States, for these varieties are grown 

 extensively there. 



HIBERNATION. 



Knowledge of the hibernation habits of the Mexican bean beetle 

 previous to the winter of 1921-22 was based on the collection of 

 very few specimens during the fall and winter. The greater portion 

 of the life cycle of many important injurious insects, especially in 

 the Temperate Zones, is passed in a dormant state during winter, 

 but in many instances little is known about this stage. Attack on 

 insects during this period has been found successful in notable cases, 

 such as the clean-up practices recommended in some localities against 

 the chinch bug, Blissus leucopterus Say, and the planting of wheat 

 to take advantage of the seasonal life history and hibernation habits 

 of the Hessian fly. Other outstanding examples might be mentioned. 



The adult of the bean beetle is the only stage which survives the 

 winter. In 1921 emergence from hibernation was first noted March 

 22, when four adults were collected on early beans. An egg mass 

 was also collected, indicating that emergence had occurred a few 

 days before. In field observations emergence and spring migration 

 lasted until the middle of May, the greatest number having emerged 

 by late April and early May. 



Restlessness of adults in the field was noted in August, 1921, and 

 from that time until late October migrations occurred. Beetles were 

 exceedingly numerous until that time, but had almost disappeared 

 from the field by November 4, when a heavy frost occurred. A few 

 specimens were observed up to November 25, 1921, on parts of bean 

 foliage which had not been killed by frost. 



Adults of the Mexican bean beetle have been found hibernating 

 under various conditions. They have been collected in old stumps 

 near a garden, in cracks of old fence posts, in debris about an old 

 fence, in stone piles near a garden, under leaves and plant remains 

 in the garden, under a woodpile, and in well-drained woodlands 

 near bean fields. 



Experience gained in California in investigating the hibernation of 

 beneficial coccinellids led J. E. Graf to believe that the Mexican bean 

 beetle, which is a coccinellid, hibernates similarly. Therefore, a 

 large area surrounding the Birmingham trucking district in the East 

 Lake section was carefully searched for the beetle during the winter 

 of 1921-22. The results are given in Table 4. 4 



This area comprised approximately 12 square miles and the same 

 territory was searched again in the winter of 1922-23. These results 

 are shown in Table 5. 



4 M. P. Foshee, D. M. Dowdell, Jr., and others assisted in this work. 

 80333°— 24f 2 



