October, '19] fink: ladybird hibernation 393 



HIBERNATING HABITS OF TWO SPECIES OF LADYBIRDS 



By David E. Fink, Truck-crop Insect Investigations, U. S. Department of 



Agriculture 



Two species of ladybird beetles have similar hibernating habits in 

 Tidewater, Va., the spotted ladybird {Megilla maculata DeG.), and 

 the squash ladybird {Epilachna horealis Fab.), the former beneficial, 

 the latter injurious. Both species vv'ere studied while the writer was 

 stationed at Norfolk, Va., the former in connection with the ladybird 

 colonization project for that region', the latter in its role as a pest on 

 watermelon. It was observed that the beetles of Megilla maculata 

 have a habit of congregating during late fall on the trunks of trees in 

 the vicinity of its feeding areas, for concealment in deep crevices or 

 under loose bark of trees as a protection during the winter months. 

 Some speculation was indulged in to account for their repeated return 

 to the same trees year after year, though it was certain, from the 

 knowledge of their life-history, that the progeny of ladybirds that 

 hibernated probably were not related any more closely than the fifth 

 or sixth generation to their ancestors that had occupied the same trees 

 previously. 



Habits of Megilla maculata 



During late fall, or after repeated heavy frosts, although aphides 

 were still present on spinach, kale and cabbage, the ladybirds left 

 these plants to find shelter elsewhere. In the locahties where they 

 had been artificially colonized, they were observed for several years 

 seeking the protection afforded by certain trees growing in the imme- 

 diate vicinity of farm buildings. They were attracted by different 

 species of trees. In one locality they hibernated every year on pin 

 oak (Quercus palustris), in another on hard maple (Acer saccharum), 

 and in other places on red mulberry {Morus rubra) and red cedar 

 (Juniperus virginiana) . 



When beginning hibernation the beetles do not alight directly on ' 

 the tree trunks, but gather on the ground about the base of a tree, ■ 

 afterwards crawling up the trunk and seeking suitable cavities or 

 loose bark for shelter. They arrive singly and by twos and a cavity I 

 soon harbors several hundred individuals, the size of the colony depend- 

 ing to some extent on the accommodation of the cavity or crevice. 

 On large trees many natural shelters occur, and the ladybirds, dis- 

 covering these, in due course divide into groups and occupy them. 

 First the cavities on all parts of a tree are occupied, but with colder 

 weather only the south and east exposures become inhabited. At no 



' Bui. 15, Va. Truck Exp. Stn., Norfolk, Va., Apr. 1, 191."). 



