THE CAUSE OF MIMETIC RESEMBLAJfCE. 587 



they easily and rapidly fall off and leave the wing bare except for 

 a marginal line and along the veins {Hemaris, TrocJiiUum). In 

 other cases again (certain Sesiidce) the scales may remain on the 

 wing, but themselves become transparent. In the numerous 

 more perfect instances the body is banded, and may gain a 

 marked " waist," while the scales upon it may belost or modiHed, 

 so that the appearance of the hard shining body of the model is 

 suggested with extraordinary exactness. 



The means adopted among Coleoptera, even in closely related 

 genera, are so curiously different tl)at a longer description, 

 accompanied by several illustrations, is necessary. 



The followiug examples are all selected from the Longicorns. 

 Tbe simplest resemblance to a wasp is that attained by the 

 common beetles of the genus Clytus, such as the Britisb C. arietis. 

 A better example is the Mediterranean species Plagionotus 

 scalaris, shown on Plate 41. fig. 3. In these cases there is 

 nothing visible to represent the wings of a wasp ; but the elytra 

 and thorax are black banded with yellow, there is a far more 

 pronounced " waist " than is usual in Coleoptera, the legs are 

 slender and wasp-like, and ai'e moved with wasp-like activity and 

 jerkiness. In spite of the apparent want of wings, the effect 

 produced is very considerable, and many persons hesitate to 

 touch the insect. This, then, is the method adopted in the group 

 of Clytince ; but in various other allied tribes, such as the Necy- 

 dalincB, the 'Bliinotragince., the EsthesimB, the Callichromince^ 

 and others, the elytra, which form by far the largest part of the 

 visible dorsal surface in the Clytince, become greatly reduced so 

 as to show the under wings, which, folded over the back or 

 expanded in flight, in either case strongly suggest the wings of 

 a wasp, or in some cases an ichneumon. Purthermore, the elytra 

 are reduced in two different w-ays — in some genera to liiiear 

 rudiments more or less broadened at their bases ; in others to 

 small subqiiadrate or oval structures representing the bases 

 alone. Grood examples of the latter are seen in JEstliesis ferru- 

 gineus {Esthesince) (Plate 41. fig. 5) from Australia, and in 

 Nothopeus hemipterus {CallichfomincB) from the Oriental Region 

 (see fig. 4). Examples of the former are shown in Isthmiade 

 braconoides {RhiiiotragincB), fig. 6, from Brazil, and in a Hephces- 

 Hon sp. {Necydalince)^ fig. 7, from Chili. 



The examples figured are merely a few selected from a laro-e 

 number, but they serve to show the different degrees to which a 



