22 



BULLETIN 1243, U. S. DEPARTMENT OF AGEICULTUEE. 



Table 7. — Data on colonies of Mexican bean beetles in hibernation, winter of 

 1922-23 {through Feb. 9, 1 928) —Continued. 



GROUP 9. 



[81 beetles in original colony, in space 5 feet by 10 feet, marked black, Dec. 20, 1922. 



Date. 



Number of 

 beetles 

 painted. 



Number of 



beetles 

 unpainted. 



Remarks. 



Dec. 20. . . 



1922. 



81 

 31 



30 

 29 

 21 

 22 







Dec. 30 



15 



19 

 19 

 12 



21 



Slightly active. 





1923. 





Jan. 12 



Slightly active. 



Jan. 31 



Feb. 9 - 









The mortality in the woods during hibernation is not as great as 

 might be expected. Remains of beetles have been found which in- 

 dicate the work of carabid beetles or other predacious enemies. The 

 high mortality in Group 2 (Table 6) is unusual. 



Records of hibernation were also obtained from cages. At Bir- 

 mingham, Ala., 17,800 beetles were placed in cage 1, and were given 

 their choice of materials which had been found by Dr. W. E. Hinds 

 to be satisfactory the previous winter. The materials used were 

 wood, sticks, cornstalks, and bean vine debris, a fourth of the cage 

 being left bare. The cage was placed under a small tree which 

 shaded it about half the day. Beetles numbering 18,050 were placed 

 in cage 2; similar to cage 1, and with similar materials, but in a loca- 

 tion a mile and a half away, where the cage was not shaded. These 

 cages were placed at an altitude of about 600 feet above sea level, in 

 latitude 33 d 31' N. 



Observations were made of cage 2 at intervals during the winter. 

 As noted in the field observations, many of the beetles moved about 

 on warm da}^s throughout the winter. 



Air temperatures were taken in the shade as observations were 

 made. No beetles were observed to be out of the hibernating ma- 

 terial below a temperature of 50° F., and very few were out at tem- 

 peratures below 60° F. At 60° F. and above, up to 70° F., from 30 

 to 200 beetles would crawl about the top of the material and on the 

 sides of the cage, depending on the amount of sunlight. Above 70° 

 F., the beetles became more active, and March 30, 1922, at 75° F., 

 724 beetles were out and active. Early spring migration and issu- 

 ance from hibernation probably took place under natural conditions 

 about that date, although the first adult was not taken on beans 

 until April 6. After March 20 the beetles in the cages were active 

 at temperatures below 60° F. on some days. April 1, when the tem- 

 perature was 45° F., 124 beetles were out. Almost all the beetles 

 hibernated under the pile of wood and sticks, several inches below 

 the surface, where the material was constantly moist. A few beetles 

 hibernated in the bean vine debris. 



In the spring, about the time appearance on the earliest garden 

 beans was expected, as indicated by observations of beetles under 

 natural conditions, beetles were removed as fast as they crawled on 

 the sides of the cage. The emergence in the cages is given in Table 



