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XV. On the Food of Gaily-coloured Caterpillars. By 

 J. W. Slatek. 



[Read 6th June, 1877.] 



Thanks to the observations of modern entomologists — 

 among whom may be especially mentioned Messrs. 

 Wallace, Bates, Belt, Jenner Weir, Butler, &c. — it is 

 now very generally admitted that insects whose striking 

 coloration is unfavourable to concealment may be ex- 

 pected to possess, in compensation, some especial means 

 of protection, whether offensive weapons, hard integu- 

 ments, a nauseous taste or a disagreeable odour. In some 

 instances, however, Ave see certain species avoided by what 

 we might consider to be their natural enemies, but we 

 remain unable to detect the reason. In other cases, 

 whilst recognizing that insects are protected by an im- 

 pleasant flavour or scent, we can throw very little light 

 upon its origin. Thus, after taking into considei'ation 

 the facts recorded by Mr. Weir and Mr. Butler in their 

 interesting papers to be found in the " Transactions " of 

 the Society for 1869, it would be a very superfluous task 

 to give further confirmation of the immunity from the 

 attacks of birds and other insect-devourers which Abraxas 

 grossulariata enjoys both when mature and when in the 

 larval condition. Almost as useless would it be to doubt 

 that this immunity must depend upon an evil taste or 

 odour, or a combination of the two. But I am not aware 

 that any clue lias yet been found to the origin of this 

 repulsive property. It seems to me that strikingly- 

 coloured insects, not otherwise specially protected, Avill be 

 found to feed upon poisonous plants, or upon such as, 

 though not poisonous, possess unpleasant, or at least very 

 powerful, odours or flavours. From such a diet I con- 

 ceive that the insects in question may receive properties 

 positively injurious, or at least disgusting, to their enemies, 

 and that a brilUant colouring may therefore here serve as 

 a danger signal, hke the quarantine flag, warning all 

 comers to keep their distance.* 



* See also Wallace, in Proc. Ent. Soc., March, 18G7. 

 TRANS. ENT. SOC. 1877. — PART 111. (oCT.) 



