192 



PSYCHE. 



[April 1889. 



remarkable than any of the others, in 

 the spread, known to be recent, of 

 Anosia plcxippus which feeds only upon 

 Asclepiadaceae^ a group of plants found 

 all over the world in temperate and 

 torrid regions. It is remarkable, because 

 Anosia belongs to a section of the sub- 

 family nearly all whose other members 

 belong to the Old World, and yet it is 

 in. the Old World that it is now achiev- 

 ing its success. In ancient times, some 

 offshoot of the Old World type found 

 its way to tlie new continent, spread 

 and multiplied, so long a time ago as to 

 have now become differentiated into 

 several different species and genera, 

 one of \\'hich, reintroduced through 

 commercial agencies into the home ot 

 its forefathers, bids fair to rival its 

 ancient allies. Here then w^e have a 

 butterfly which may yet become as 

 cosmopolitan as ]'aiiessa carditi is 

 to-day, or only less so from its inability 

 to perpetuate itself in regions with 

 severely cold winters. 



I do not find among our butterflies 

 any other instance which seems to me 

 likely to aspire to similar honor. But 

 it may be pointed out that Pier is rapae 

 is by no means so destructive in Europe 

 as is another butterfly of the same group, 

 Maiicipium brassicae whose caterpil- 

 lars, being semigregarious, are capable of 

 much more mischief. Should this butter- 

 fly be transported to America (and its 

 chances of such transportation seem to 

 be equally good with those of Pier is 

 rapae), it would probably outdo the 

 ravages of Pier is rapae and spread as 

 far as it. 



Considering the relative abundance in 

 individuals of the species of Rhodoce- 

 ridi abo\e that of those of any other 

 tribe of butterflies, the prevalence of 

 Eiirymi in the north temperate 

 regions, and that of Callidryades in 

 the tropics of the New World, it 

 seems a little surprising that we have 

 among them no single species which 

 has a range at all extraordinary, and 

 no exainple of w^idespread distribu- 

 tion through two hemispheres. At least 

 such must be the judgment of one who 

 cannot look upon two forms having an 

 entirely diflerent development in two 

 hemispheres, as holding any right to be 

 considered otherwise than as now dis- 

 tinct species. But there are others wdio 

 claim an identity of species between 

 some of the forms of Enrymjis on the 

 two northern continents. In one case, 

 indeed, it would appear that one of our 

 common species of Eiirymjis^ E. philo- 

 dice. was introduced by some accident 

 into England, and flourished there for a 

 brief while, but speedily became extinct. 

 It seems almost equally surprising, 

 considering the dependence of insects 

 upon their food plants, that we find 

 not a single instance of any remark- 

 able distribution among butterflies feed- 

 ing in their caterpillar state upon 

 Legumiiiosae or upon grasses, although 

 a very considerable number of butter- 

 flies aftect these particular groups. It 

 is, therefore, plain that besides the uni- 

 versal distribution of its larval food 

 plant, something more is needed to open 

 before any butterfly the possibilities of a 

 cosmopolitan life. 



