52 BUTTERFLIES 



" There Is yet another and more curious instance of 

 our butterflies confirming the arrangement of plants in 

 Bentham and Hooker's ' Genera Plantarum.' Ageronia 

 and Didonis were formerly widely separated by lepi- 

 dojjterists, being even considered as constituting dis- 

 tinct families, but now they are to be found beside one 

 another among the Nymphalinae, and the structure of 

 their caterpillars leaves no doubt about their close affin- 

 ity. The caterpillars of Ageronia feed on Dalecham- 

 pia, those of Didonis on Tragia. Now these two 

 Euphorbiaceous genera were widely separated by 

 Endllcher, who placed the former among the Euphor- 

 bieae, the latter among the Acalypheae ; Bentham and 

 Hooker, on the contrary, place them close together in 

 the same sub-tribe of Plukenetieae, and thus their close 

 affinity which had been duly appreciated by butterflies 

 has finally been recognized by botanists also." 



The narrow choice of certain species is perhaps 

 indicated in our own fauna by what we know of 

 the food plant of the Pearl Crescent (Phyciodes 

 tharos). So far as w^e know it feeds only upon 

 a single species of Aster ; " and if your butterfly 

 selects only that," said the late Dr. Gray when 

 I told him of this, " it is a better botanist than 

 most of us." Only one other plant has been 

 alleged as its food and that probably by mistake. 

 This special Aster the female selected out of many 



