LIFE AND HABITS. 11 



The food of these beetles is well known to consist principally of aphids. 

 Certain coccids are eaten by some of the species, but this is the exception. 

 A coccid of the chestnut constitutes one of the principal foods of Cycloneda 

 iida at Cold Spring Harbor. This coccid is not eaten by any of the 

 other species. MegiUa fuscilabris is also peculiar in its food habits, for it 

 eats a much larger proportion of pollen and fungus spores than are eaten 

 by the other species. In general, coccinellids eat a wide range of species 

 of aphids. Some species of aphids are found to be especially attacked by 

 some species of lady-beetles; thus, that of Rhamnus cathartica apparently 

 is attacked only by 'Adalia bipunctata at Cold Spring Harbor. This may be 

 partly attributable to its early and short season. Upon the willow, Adaliu 

 bipunctata, with only rarely a specimen of Harmonia picta, is found on 

 Long Island. The preference of Coccinella monticola for the larch has 

 been observed by Dr. G. W. Dimmock. At Cheney, Washington, the aphid 

 of the box-elder is especially attacked by Adalia. Other preferences of 

 coccinellids outside of the groups here treated, such as those of Chilocorus 

 similis, Pentilia, and Vedalia, are well known in the literature of economic- 

 entomology. The species of Hippodam ia and Coccinella, however, show 

 fewer preferences and are therefore found in more general competition. 

 I have elsewhere published further data in regard to the food of lady 

 beetles. (Johnson, 1906.) 



Epilachna, as is well known, differs in being solely a leaf -eater. In this 

 genus the species differ more in their food, for E. borealis eats the leaves 

 of the cucurbits, while E. corrupta eats those of the bean. 



Sexual attraction is especially powerful in the lady-beetles, since so large 

 a proportion of them are seen in copulation. This is partly due to the 

 prolonged time of copulation. But when the pairs are associated, the male 

 nearly always attempts mating at once. Mismatings of species with spe- 

 cies and even family with family have been recorded more often, I think, in 

 the coccinellids than in any other family. This is significant in connection 

 with sexual selection, for, where promiscuity prevails, as it does here, the 

 chance of either preferential or assortative mating is decreased. A female 

 may lay fertile eggs as long as 3 months after mating and possibly longer. 

 The beetles are emerging at intervals throughout the summer, the broods 

 overlapping. Promiscuity is, therefore, an advantage in this species, for 

 if the male did not mate or attempt to mate frequently, many of the 

 females would lay batches of sterile eggs before being fertilized, as this 

 is their habit when reared and not provided with mates. 



The eggs are laid in successive batches of 1 to 40, most frequently about 

 20, at intervals of a few days for an extended period. The competition 

 between the larva? of one batch is frequently very severe, because the 

 existence of the colony of aphids which excited the female to lay her eggs 

 is vicissitudinous. Aphids suffer from attacks of lace-wing flies, syrphids, 

 and diseases. The latter two causes of death are especially serious and 

 frequently destroy a whole colony of aphids upon which a fraternity of 



