October, '19] ' FINK: ladybird hibernation 395 



trees every year is as follows: Megilla maculata feeds almost entirely 

 on aphides which occur on various crops in near-by fields. As cold 

 weather approaches the aphides breed in larger numbers on crops 

 that are more or less protected, as in fields nearest buildings or trees. 

 Such places are also more favorable to a longer activity of the beetles. 

 The tendency, therefore, is for the ladybirds gradually to drift from 

 outlying portions of a field to places near the protected parts where 

 food is more abundant. In any given locality the conditions are the 

 -same year after year, so that at the end of the growing season the 

 majority of the beetles are in the neighborhood of trees that are excel- 

 lently adapted for the purpose of tiding them over the winter months, 

 irrespective of the fact that these same trees were used the previous 

 year for the same purpose by the ladybirds' predecessors. 



Habits of Epilachna borealis 



The squash ladybird possesses the same habit of seeking trees for 

 protection during the winter, although it undoubtedly hibernates in 

 other places. Beetles of this species, however, do not always return 

 to the same trees, as is the case with Megilla maculata, because their 

 main food plants are often shifted from one locality to another. Rota- 

 tion is a very common and successful practice in watermelon culture, 

 the same field not being used a second time for this crop until the lapse 

 of four or more years. In other respects the hibernation habits of 

 these two species are identical; indeed, in the watermelon regions of 

 Virginia the two species are commonly found hibernating together. 



The fact that they do not inhabit the same trees every season was 

 determined as follows: In one locality they hibernated on hickory 

 (Hicoria glabra). The following year they were observed on two 

 large persimmons (Diospyros virginiana) growing in the center of a 

 watermelon field, and other individuals were found on pines bordering 

 the same field, but none of the ladybirds occurred on the hickory tree 

 that they used the previous season, although the fields were only 500 

 feet apart. In another locality the ladybirds were observed one sea- 

 son hibernating in old apple trees on the border of a watermelon field. 

 The following year they hibernated on a row of red cedar {Juniperus 

 virginiana) , and none were found on the apple trees. 



The habit of this species of seeking winter quarters according to 

 •convenience seems to confirm the conclusion drawn with respect to the 

 accidental return of Megilla maculata to the same trees. Both species 

 are guided in their choices by their feeding habits. With the former 

 the conditions are more or less fixed, while with the latter crop rotation 

 involving the insect's food plant causes the beetles to migrate from 

 field to field. 



