10 EVOLUTION IN COLOR-PATTERN OF THE LADY-BEETLES. 



This cause will be discussed after the presentation of the data. It is 

 referred to here that the reader may bear in mind the question of utility 

 versus determinate evolution as the species and varieties are described. 



LIFE AND HABITS. 



It is not necessary to give any detailed account of the habits of these 

 insects for the purpose of this article. Only those features will be selected 

 that are significant for this discussion of the color-evolution. Lady-beetles 

 are probably well protected from predaceous animals by their distasteful- 

 ness, as shown by the experiment with the catbird. In the localities 

 where they are abundant I have never seen them attacked. Frequent 

 causes of death are parasitism by internal insect larvae, an unknown dis- 

 ease, and difficulty in casting the larval skins on emergence from the pupa ; 

 but the two great causes of death are hibernation and the maldistribution 

 of eggs. Any considerable advantage in either of these respects would be 

 strongly favored by natural selection. 



Epilachna is uncommon in the spring at Cold Spring Harbor until the 

 new brood comes forth, when it is quite abundant. Efforts to hibernate 

 it under as favorable conditions as I could arrange succeeded in not 

 more than 50 per cent of the individuals. Attempted hibernation with 

 other species was unsuccessful, although some, when provided with food, 

 overlived the winter in the vivarium. The critical conditions seem to bo 

 extremes of dryness and moisture. Mec/illa maculata hibernates, at least 

 frequently, in masses, one of which was found and kindly sent me by Dr. 

 Robert W. Hall, of Lehigh University. I am assured by Prof. N. F. Davis, 

 of Bucknell College, that in the spring such a mass was seen to mount a 

 fence-post preparatory to flight. In the Western States Hippodamia con- 

 vergens and spuria resort to the same practice. Strangely enough, such 

 masses were frequently found on mountain-tops throughout the Western 

 States. This is probably not adaptive, but a by-product of some tropisms. 

 These beetles are found in great numbers in the flotsam of the shore of 

 large bodies of water when a certain sequence of winds occurs during 

 the time when large numbers are in their long flight. The ability to collect 

 large numbers on mountain-tops and shores has been a favoring circum- 

 stance to the collection of material for this paper. I would like here to 

 solicit the opportunity of examining any such masses, and I will gladly 

 return them if desired. 



While these beetles fly very little in cloudy weather, on warm sunny days 

 they frequently take long flights. This is important as breaking down 

 the probability of isolation, widening the range of varieties, and making 

 their passage into species more difficult. Dispersal is probably even more 

 effective than in birds, which have such powerful homing instincts, 

 although of course the occasional storm-driven bird frequently gets much 

 farther astray. 



