1064 THE BUTTERFLIES OF NEW ENGLAND. 



ceridi, congregate in damp spota. The larvae feed on leguminous plants, 

 especially on Cassia. 



The eggs are described as fusiform, more strongly so than in Eurymus 

 with very numerous ribs. 



The caterpillars are greenish gray with a pale stigmatal hand and fre- 

 quent short hairs mounted on conical tubercles, much more prominent, 

 especially on the head and thoracic segments, than those of Eurymue, 

 which genus in general the caterpillars resemlile. 



The chrysalids somewhat resemble those of Callidryas, having greatly 

 protuberant wing cases, a long, conical, frontal prominence bent slightly 

 upward, and on the thorax a slightly arched and compressed dorsal crest. 

 They are green with numerous small, scattered, black spots and a pallid 

 line along the whole side of the body. 



EXCURSUS XLI.—THE COLONIZATION OF NEW ENGLAND. 



Trembling with joy awhile she stood, 



And felt the sun's enlivening ray: 

 Drank from the skies the vital flood, 



And wondered at her plumage gay ! 

 And balanced oft her broidered wings. 



Through fields of air prepared to sail : 

 Then on her vent'rous journey springs, 



And floats along the rising gale. 



The Butterfly's Birthday. 



When discussing in a former excursus tiie })uttertlies common to the 

 Old and New Worlds, we pointed out how much closer was the relation- 

 ship between the butterflies of the two hemispheres in the high north than 

 in the northern temperate zone. If we could go back in time to the 

 warmer tertiary periods, we should no doubt, in these same regions, find 

 a complete or nearly complete unity of type between the butterflies of this 

 hemisphere and of the Old World. At the present time, as we go farther 

 and farther south toward the tropics, the distinction between the assemblages 

 in the two worlds becomes greater and greater, until in the tropics them- 

 selves we probably should find scarcely a genus identical in the two hemi- 

 spheres, and not infrequently whole tribes peculiar to one or the other 

 world. It will be evident from this that some parts at least of the 

 present butterfly fauna of New England find their nearest allies in the north ; 

 indeed a few of the species belong more properly to the subarctic regions 

 than they do to New England itself. And if we were to judge of the 

 derivation of the present fauna of New England by the geographical distri- 

 bution of its members and of their nearest allies we should discover that 

 the facts which this method of investigation yields (and it seems to be a 

 fair method) entirely agreed with the demands of the geologists that we 

 should regard a recent condition of New England to have been one of com- 

 plete submergence under ice and snow, a condition of things forbidding its 

 being the home of any butterflies whatsoever. 



