PART I. 



INTRODUCTORY CONSIDERATIONS. 



The lady-beetles were considered desirable for this study because their 

 variability, distribution, and taxonomy indicated that they had been 

 recently and are probably now in an active state of evolution. The prac- 

 tical advantage that they could be obtained in considerable numbers from 

 many localities and could be experimentally bred was, then, decisive in 

 their favor. 



All of the American coccinellids which could be obtained in numbers 

 and which showed a variable color-pattern were studied, viz, Hippodamini, 

 CoccinellaB, and Epilachnini, divisions employed by Casey (1899). 



The Epilachnini differ from the rest of the family in being leaf-eating-, 

 in having longer generations, and in hibernating necessarily in the winter; 

 whereas the other coccinellids which eat aphids, fungus spores, and pollen 

 will remain active during the winter in a vivarium and give many more 

 generations. The difficulties of keeping a large and constant stock of 

 aphids on hand and keeping the beetles free from diseases, especially such 

 as result from dampness in the late summer and irregular temperatures 

 in the winter, proved to be very serious and prematurely shortened many 

 pedigrees. These difficulties also decreased the numbers which could be 

 successfully managed. Nearly all the pedigrees, however, are given, 

 for when too fragmentary to have much value in the study of dominance 

 and segregation, they are, nevertheless, of value in showing the transmissi- 

 bility of some characters and variation from the parent. 



The dorsal color-pattern in all the American species within these groups 

 is given for the sake of completeness, although for some species but 

 little variation data was obtainable. Tnis fact, together with the necessity 

 of carrying in mind the data of vari ition and distribution in discussing 

 experiments upon any given species, has led me to arrange the presenta- 

 tion according to species, after this ntroductory section. Furthermore, 

 this arrangement will be more advar tageous for those whose interest in 

 this contribution is primarily taxonomic. 



Every considerable new accession of data involves another revision of 

 these tribes, since there has been so much disagreement among the authors 

 and since the lines between varieti js and species in these remarkable genera 

 are so doubtful. I am obliged, therefore, to present a revision of my own 

 in order to have a suitable nomenclature. Since the revision is not an 

 end in itself, I have not givrn full descriptions, but only discussed and 

 illustrated the color-pattern of the parts studied, although of course the 

 revision is based upon many characteristics. 



Not having studied the structural features of the foreign species, I have 

 not ventured to revise the genera and have simply adopted the genera 

 as used by Casey. 



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