238 THEORIES OF MIMICRY 



act upon these alone to the exclusion of all other sets. 

 No assistance can be obtained from the conclusion that 

 the results are recent and therefore superficial, and that 

 a resemblance in deeper characters will follow in time. 

 In the first place, the examples of more perfect (and pre- 

 sumably older) resemblance show no more tendency 

 towards approximation in characters which do not help 

 to produce likeness, than the examples in which the 

 resemblance is comparatively rude (and presumably 

 recent in origin). In the second place, deep-seated parts 

 of the organism are affected when the superficial resem- 

 blance is thereby increased, but not otherwise. To take 

 a single example, the common British Longicorn, Clytus 

 arietis, strongly suggests the appearance of a wasp, partly 

 because of its black and yellow banding, but even more 

 because of its alert and wasp-like movements. This 

 implies, of course, appropriate changes in its nervous and 

 muscular systems. Although Clytus arietis is a rough 

 and imperfect example of Mimicry, the resemblance, such 

 as it is, chiefly depends upon deep-seated structures. 

 We are, in fact, led to infer in Clytus and in an immense 

 number of other mimics that the deep-seated modifications 

 were the origin of the resemblance, and that the superficial 

 modifications of colour, &c., followed later. 



The subject is, perhaps, of sufficient interest to warrant 

 the production of another example, in which the changes 

 in deep-seated structures are of more importance than 

 anything else in determining the resemblance. I know 

 of no more striking instance than the movements and 

 attitudes of the young (Lepidopterous) larvae of Endro- 

 mis versicolor, the ' Kentish Glory ' moth, rendering them 

 extremely like the larvae of saw-flies (Phytophagous 

 Hymenoptera). Numerous experiments have convinced 

 me that the latter are almost invariably distasteful. 

 During the early stages of their growth the moth larvae 

 ' arrange themselves in small groups upon the leaves and 

 leaf-stalks of the birch, and when disturbed they raise the 

 anterior part, bending the head over the dorsal surface 

 of the posterior part of the body. In this attitude they 

 strongly remind the observer of those Tenthredo larvae 



