238 



Tin:ORIES Ol- 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 presumabl)- 

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

 of the or^^anism arc affected when the superficial resem- 

 blance is thereby increased, but not otherwise. To take 

 a single example, the common British Longicorn, Clytus 

 arictis, 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 

 musc.dar systems, Althoucrh Clyhis aric/is is a rou<>h 

 and imperfect example of Mimicr)'. the resemblance, such 

 as it is, chiefiy 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 reseml)lance. 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 arc 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 End) o- 

 ))iis versicolor, the * Kentish Glor)- ' moth, rendering them 

 extremely like the larvae of saw-flies (Ph)topliagous 

 1 U'nKnoptera). Numerous experiments have convinced 

 me that the latter are almost invariably distasteful, 

 louring 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 the)' 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 



