24 



BULLETIN 1243, U. S. DEPARTMENT OF AGRICULTURE. 



maximum emergence, estimated from observations, probably 

 occurred from May 10 to May 27, which is three weeks later than at 

 Birmingham, Ala., where cages were placed at 600 feet above sea 

 level, at 33° 31' N. latitude. The insect at the latitude and altitude 

 of Lookout Mountain remains in hibernation from 1\ to 8 months. 



Table 9. — Data on hibernation cage at Chattanooga, Tenn., on Lookout Mountain, 



ivinter of 1921-22. 



Beetles collected at Birmingham, Ala. 



Beetles emerged. 



Date. 



Number. 



Date. 



Number. 



Oct. 5. 

 Oct. 6. 



6,000 

 12, 000 



Apr. 26. 

 May 16. . 

 May 18.. 

 May 27.. 

 June 10. 



37 



465 

 585 

 629 

 24 



Total. 



18,000 



Beetles transported to Chattanooga and placed in 

 cage Oct. 11. 



Total . 



1,740 



Next observation was June 29, when there were no 



living beetles in the cage. 

 Percentage survival 9. 7 



HIBERNATION AT THOMASVILLE, GA. 



The isolated infestation at Thomasville, Ga., offers an interesting 

 comparison of the habits of the Mexican bean beetle at a low alti- 

 tude (about 300 feet above sea level) and more southern latitude 

 (30° 54' N.) with those at the higher altitudes and more northern 

 latitudes' of Birmingham, Ala., and Lookout Mountain, Tenn. 



Hibernating habits under natural conditions at Thomasville, 

 Ga., during the winter of 1921-22 were very similar to those about 

 Birmingham, Ala. Because of the lighter infestation and the rela- 

 tively smaller acreage of bean plantings, adults were not so numerous. 

 An area of several square miles surrounding the city was included 

 in the study of hibernation. A total area of 4,823 square feet, 

 representing 718 searches, was examined carefully. Of 152 adults 

 observed in hibernation, 69 per cent were found in a colony com- 

 prising 105 beetles. These were found at the base of a large oak, 

 growing in contact with a large gum tree. The beetles were dis- 

 tributed from 1 to 3 inches below the surface in oak and gum leaves. 

 Close by was a garden which had contained pole Lima beans which 

 had been destroyed by the beetle the previous summer. 



In searching for hibernating bean beetles many adults of the 

 related squash beetle 5 were also observed in hibernation, often 

 under identical conditions, side by side, under leaves on the ground. 

 The well-known habit of the squash beetle of hibernating in crev- 

 ices in the bark of trees has not been observed in the case of the bean 

 beetle. 



A hibernation cage like those mentioned above was used at Thomas- 

 ville. (See Table 10.) In 1921 the majority of the beetles left 

 the fields late in October, but a few were present as late as Decem- 

 ber. The first issuance from hibernation observed in the field was 

 March 29, 1922, but, as noted in Table 10, emergence began February 

 28 in the cage and continued until June 3. The survival was 30 



&Epilachna borcalis Fab. 



