192 



THE AMERICAN ENTOMOLOGIST. 



tional pattern is an almost exact connterpart of 

 the Danais that is figured above.* So servilely 

 indeed does it mock the other species, that 



[Pis 133 ] 



t olol'to — Copptiy-iol, bUck ami ^Ii'tc 



Prof. Jaeger, in his Life of JSforth American 

 Insects, has actually favored his readers with a 

 wood-cut of it, and gravely informs them that 

 its scientific name is Danais arcMppus! And 

 yet - close as the resemblance is, and common 

 as both species are — no author seems hitherto 

 to have observed, that we have here a clear case 

 in North America of that very same curious 

 imitative process, which eight years ago was 

 so beautifully expounded and explained by Mr. 

 Bates, so far as regards the butterflies of the 

 Valley of the Amazon! 



The larva of this Disippus butterfly, of which a 

 drawing will be found below (Fig. 134 «,), occurs 



[Fig. 134.] 



most commonly on dilTcrent species of willow, 

 but is often found on the closely allied poplar 

 and Cottonwood (pojnilus) and occasionally on 

 the plum. There is another larva, which 

 resembles it so closely that the two can scarcely 

 be distinguished, and which normally, like most 

 species of the genus NymphaUs, inhabits. the 

 willow, bnt is occasionally mr( wilb on scrul)- 



* In Figure 133, the left wings repvf.^.iii ili, nil" r .uii'aci , 

 and the right wings, whicli arc di-larh. il ii,,ni ihr Ijm.Iv, 

 represent the lower surfciee. The dincr.-m-r in tlir colorii- 

 tion of the two surfaces is but slight in this sjiecies, ncitlicr 

 does it amount to much in the Archippui buttcrlly ; bnt iu 

 oome butterflies it is very oonsiderablB. 



oak (QttercAis ilicifolia), on whortleberry, on 

 cherry, and on plum, fi-om which last tree we 

 have ourselves bred a single specimen. This 

 second larva produces the Ursula butterfly 

 {Nym'jjhaUs Ursula, Fabr.), a species belonging 

 to the same genus as the ZJmyj/JW* butterfly, but 

 differing widely therefrom in being of a sombre 

 blue-black color, witli its wings bordered both 

 above and below with blue, and below with a 

 scries of dull orange spots inside the blue 

 border. Place this insect side by side with (he 

 ArcMppus l)Utterfly, and everybody would say 

 at once that no two species could possibly be 

 nioie unlike in the general style of their colora- 

 tion. Clearly, therefore, it cannot be considered 

 as in any wise mimicking tlie latter. Now, the 

 Ursula butterfly is found every whei-e through- 

 out the Northern States wherever (he Disippus 

 butterfly is met with; and yet, while the latter 

 is a common and abundant species, the former 

 is everywhere quite i-are.* To what are we to 

 attribute this fact? It can scarcely be owing to 

 structural differences in tlie external organiza- 

 tion of the two species ; for the two belong to 

 one and the same genus. Tt surely cannot be 

 because the larvas of the former are more 

 exposed to the attacks of predaceous animals 

 than those of the latter; for they inhabit the 

 same, or very 'nearly the same trees, and in size, 

 shape and general coloration the two are almost 

 exactly alike. Certainly it can not be because 

 tlie pupic of one species are more subject to be 

 devoured by birds, insects, etc., tlian those of 

 the other i-pecies; for it is Impossible to tell one 

 jiupa from another, when ])laced side by side. 

 The only cause to which we can reasonably 

 uUribute the great abundance of the Disijypus 

 butterfly and the compai'ative rarity of tlie 

 Urt.ula butterfly is, that the former mimicks the 

 Archlppiis butterfly, as has been shown above, 

 and isi consequently often mistaken by tree-fi'ogs, 

 dragon-flies, Asilus flies and other beasts of prey 

 for its unsavory prototype and allowed to escape 

 with impunity ; while the latter, being too hon- 

 est a bug to assume a fraudulent and deceptive 

 disguise, is ruthlessly devoured by every insect- 

 eating animal that can get hold of him. 



Figure i;U h, sho-wstha Disippus butterfly in 

 the pupa state, with Ihc strange knife-edged 



.\i-conlin^'li> .Mr. liilliniis, w Ik. iii.e& iii>t >eiiii tii liave met 

 with any ursula at all, disipiiusU ' ' very commuu Irom July 

 to October" in Canada West. {Canad. Entovi., I., p. 45.) 



