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On the origin of the genus Anthocharis, Bdv. 



(= Euchloe, lib.) 



By T. D. a. Cockerell. 



These delicate little butterflies, belonging to the genus Anthocharis 

 of Boisduval, seem at first sight very aberrant members of the Pieris 

 stock, with their one brood a year, narrow wings, and (in many species) 

 orange apical patches on the forewings. 



Yet in examining their characters as compared with those oi Pieris, 

 I have been driven to the conclusion that Anthocharis is by no means an 

 ancient genus — as genera go — and that it arose directly from an old 

 Pieris stock, and that probably on the American continent. 



In stating the facts which have seemed to me to support such a 

 view, it will be useful to review the peculiarities of the genus .4«///oc/z(7n.s-, 

 and show how thev may have arisen as offshoots from the stock from 

 which the genus Pieris has also directly come. 



Single-broodedness. — li> Europe, Pieris bryonice of the Alps and far 

 north is generally assumed to be the one-brooded ancestor of the double- 

 brooded P. napi oi the lowlands, and there is a tendency to assume that 

 multiplication of the brood is a direct result of a warmer climate, and 

 the idea of a single-brooded species arising from a double-brooded one 

 seems not often to be entertained. 



However, taking this same «<7/i/ group in North America, we have 

 still the assumed primitive type, bryonice, and likewise the forms oleracea 

 and venosa to represent the European napi — so far the analogy is com- 

 plete — but then we are met with what seems a strange anomaly, Pieris 

 virginiensis, a delicate pale-winged form, appearing as a rare aberration 

 in New York and Ontario, but actually as a spring-emerging one-brooded 

 species in West-Yirginia, — just exactly as if it were an Anthocharis, in 

 fact! From this 1 think we get a clue as to the origin oS. Anthocharis — 

 it did not arise from a one-brooded arctic form like P. bryonice, but was 

 rather a branch from a stem which was probably eve7i then double- 

 brooi'.ed — and that accounts for its pallor and delicacy of structure, as- 

 fits an insect of the temperate zone. 



Orange-tips. — Those species o^ Anthocharis which I regard as com- 

 ing nearest to the' primitive type of the genus,* do not present orange 

 tips, but since these orange patches are so characteristic of many species 

 it will hardly do to overlook them. In the first place, they are developed 

 in the males — which seems to show that they are of the nature of second- 

 ary sexual characters, and have perhaps been perpetuated as such from 



* See also Darwin, "Descent of Man," 2nd Ed., p. 312. 



