BUTTERFLIES AS BOTANISTS. 1595 



has reareil butterflies might expect, since he must often have found that 

 under no consideration would a given caterpillar teed upon anything what- 

 ever but its own pet food plant. This is more striking because of the 

 polyphagous nature of others, such as Jasoniades glaucus, which feeds upon 

 plants belonging to no less than fifteen different families. 



In many, perhaps the majority, of instances the plants upon which 

 allied species or genera of caterpillars feed themselves, belong to allied 

 families of the botanical systems ; and Fritz Midler brings forward some 

 curious instances in which a knowledge of the habits of butterflies would 

 have led, had they been followed, to an earlier recognition of the affinities 

 of certain plants. Thus he says (Nature, xxx : 240) : — 



"The caterpillars of Mechanitis, Dircenna, Ceratinia and Tthomia feed 

 on different species of Solanaceae (Solanum, Cypliomandra, Bassovia, 

 Oestrum) , those of the allied genus Thyridia on Brunfelsia. Now this latter 

 genus of plants had been placed unanimously among the Scrophularineae, 

 till quite recently it was transferred by Bentham and Hooker to the 

 Solanaceae. Thus it appears that butterflies had recognized the true 

 affinity of Brunfelsia long before botanists did so. 



"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 

 lepidopterists, being even considered as constituting distinct 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 affinity. 

 The caterpillars of Ageronia feed on Dalechampia, those of Didonis on 

 Tragia. Now these two Euphorbiaceous genera were widely separated by 

 Endlicher, who ])laced the former among the Euphorbicae, 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 Phyciodes tharos. So far as 

 we know it feeds only upon a single species of Aster ; "and if your butter- 

 fly 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 furnished it by Mr. Mead whereon to lay her 

 eggs and no one has yet reared it upon any thing but Aster novae-angliae. 

 Considering the difficulty that botanists have with the species of this group, 

 such restriction of choice, if really true, certainly indicates some keen per- 

 ception on the part of the butterfly. 



Now with exceedingly rare exceptions the eggs of butterflies are laid 



