78 SAMUEL H. SCUDDER. 



sequeutly if the Swallow-tails are placed highest in the scale, the 

 Pierids must go with them; nobody questions this; yet the Plerids 

 2iOHsess not a single one of the characteristics by which a high rank is 

 claimed for the Swalloio-tails. Commentary upon this is needless. 



Further than this, in several features now to be mentioned, we may 

 trace a regular progression in passing from the lower to the higher 

 butterflies. These features indicate with little doubt the actual pro- 

 gress of events in the geologic history of higher lepidopterous life, 

 and leave a record of advance which is completely falsified by re- 

 moving the Swallow-tails to the summit of the order. Attention has 

 been drawn to one of these features by Bates, who, at the same time 

 proposed one of the most rational systems yet advanced ;* it has how- 

 ever been known and used in dividing butterflies since the time of 

 Linne and Greoff"roy.f I refer to the structure of the legs, where 

 fundamental distinctions occur among butterflies. In the lowest family 

 or skippers, as in the moths, all the legs are developed to an equal 

 extent; they only differ in proportional length. In the Swallow-tails 

 and in all the other members of the family of Papilionidte this also is 

 true. But the moment we leave these two lower families, a change 

 appears in the front legs and progresses regularly. In the gossamer- 

 winged butterflies all the legs of the females are alike, but the front 

 pair of the male is variously aborted ; in the Lycjenids the tarsi of 

 this sex have lost the terminal claws and are densely spined beneath ; 

 even within this group we can trace gradations, the claws being first 

 replaced by a single curving spine, and then by a pair of straight 

 spines only a little longer than the others; in the Erycinids, the tarsi 

 are spineless, and the joints are reduced from five to two or even one. 

 In the highest family, the brush-footed butterflies, atrophy of the fore 

 legs has reached both sexes, so that they are practically useless, al- 

 though the atrophy is much more excessive in the male ; the legs of 

 the female are greatly reduced in size, and lack the terminal arma- 

 ture; while in the male of the highest groups, they are exceedingly 

 diminutive, and the tarsi are reduced to a single minute joint. Now 

 when we remember that this atrophy aff"ects only the legs borne by 



* Journ. Eut. I, 218—22. (1861); II, 175—77, (1804); Traus. Linn. Soc. Lond. 

 XXIII, 515, (1862). 



fSee particularly Dalinan's admirable paper; Forsok till systematisk Upp- 

 stiillning af Sveriges Fjarilar, (Vetensk. Acad. Handl. XXXVII, 48 seq. 1816); 

 or the abstract of it in Oken's Isis, (1824, 416 seq.), Ilis classification has been 

 pretty closely followed by his countryman Wallengrea, (Lepidopt. Scand. Rhop. 

 8*^ Malmo, 1853). 



