MEXICAN BEAN BEETLE IN THE SOUTHEAST. 19 



The largest numbers of hibernating beetles have been found in 

 woodlands where the land is rolling. In all cases where living 

 beetles were taken, the material sheltering them was moist and was 

 protected from driving winds. As this material dried out, during 

 warm weather, the beetles moved about and went farther into the 

 material where moisture was present, or migrated to more favorable 

 quarters. 



In sections where the infestation is extremely heavy there is a 

 tendency toward hibernating gregariously. About Birmingham, 

 Ala., in the winter of 1921-22, 56 per cent of the 2,290 beetles 

 observed were found in colonies. The following winter, 1922-23, 

 only 14.8 per cent as many beetles were found per unit of area as 

 during the previous winter. This was probably due to the lighter 

 infestation during 1922. 



The largest colony observed contained 329 beetles on December 

 15, 1921, and the majority of beetles occurred in a space 18 inches 

 square. The colony shown in Plate X, A, B, contained 149 beetles, 

 more than 50 of which were in a space less than 1 foot square, about 

 1 inch below the surface. This colony was under pine needles and 

 oak leaves which had accumulated under a pine branch on the 

 ground. 



During cold weather in January adults withstood submersion in 

 water for two days with no mortality. Fifty per cent of the beetles 

 survived after submersion for four days, and one beetle was living 

 after six days. In small hibernation cages which were not sufficiently 

 moist all beetles succumbed. 



Males and females occur in approximately equal proportions. 



The few beetles which remain in the bean fields during winter 

 are undoubtedly a factor in the spring infestation, but the large 

 majority of adults migrate from the fields to wooded hills. The 

 proper moisture conditions for successful survival of the winter 

 appear to be an important factor in determining the location chosen. 

 These conditions are only constant under branches and leaves in 

 the shade, or in deep piles of material. The preferred material in 

 the Southeast is a mixture of pine needles and oak leaves. (PL X.) 

 The beetles are found distributed through the material at a depth 

 of an inch or more, depending on the moisture conditions. Adults 

 are occasionally found with colonies of the beneficial ladybird, 

 Megilla maculata DeG. 



October 3, 1922, three beetles were observed in hibernation in 

 woodlands when the shade temperature was 82° F. Three days 

 later 25 beetles were found in the same place. 



During the mild winters of the Southeastern States the adults 

 are not entirely inactive. On warm days they move about, and in 

 the course of the winter the majority change location. Some of 

 the colonies of beetles found in woodlands were watched throughout 

 the winter. Each beetle was marked with a waterproof mark. 

 Brief records of the observations are given in Tables 6 and 7. 



