ANALOGICAL RESEMBLANCES 465 



naturalist, struck with a parallelism of this nature, by arbi- 

 trarily raising or sinking the value of the groups in several 

 classes (and all our experience shows that their valuation 

 is as yet arbitrary), could easily extend the parallelism over 

 a wide range; and thus the septenary, quinary, quaternary 

 and ternary classifications have probably arisen. 



There is another and curious class of cases in which close 

 external resemblance does not depend on adaptation to sim- 

 ilar habits of life, but has been gained for the sake of pro- 

 tection. I allude to the wonderful manner in which certain 

 butterflies imitate, as first described by Mr. Bates, other and 

 quite distinct species. This excellent observer has shown 

 that in some districts of S. America, where, for instance, an 

 Ithomia abounds in gaudy swarms, another butterfly, namely, 

 a Leptalis, is often found mingled in the same flock; and the 

 latter so closely resembles the Ithomia in every shade and 

 stripe of colour and even in the shape of its wings, that Mr. 

 Bates, with his eyes sharpened by collecting during eleven 

 years, was, though always on his guard, continually deceived. 

 When the mockers and the mocked are caught and compared, 

 they are found to be very different in essential structure, and 

 to belong not only to distinct genera, but often to distinct 

 families. Had this mimicry occurred in only one or two in- 

 stances, it might have been passed over as a strange coinci- 

 dence. But, if we proceed from a district where one Leptalis 

 imitates an Ithomia, another mocking and mocked species 

 belonging to the same two genera, equally close in their 

 resemblance, may be found. Altogether no less than ten 

 genera are enumerated, which include species that imitate 

 other butterflies. The mockers and mocked always inhabit 

 the same region; we never find an imitator living remote 

 from the form which it imitates. The mockers are almost 

 invariably rare insects; the mocked in almost every case 

 abound in swarms. In the same district in which a species 

 of Leptalis closely imitates an Ithomia, there are sometimes 

 other Lepidotera mimicking the same Ithomia : so that in the 

 same place, species of three genera of butterflies and even a 

 moth are found all closely resembling a butterfly belonging 

 to a fourth genus. It deserves especial notice that many of 

 the mimicking forms of the Leptalis, as well as of the mim- 



