IMPORTANCE OF ATTITUDE IN MIMICRY 227 



of a brightly coloured model. ^ Again, instincts are 

 modified so long as the assumed attitudes and move- 

 ments are needed to correspond with the false appear- 

 ance of inedibility, but when these are no longer helpful, 

 rather a danger, the recently acquired instinct of deceit 

 is abandoned, and the more deeply seated instinct of 

 flight comes into action. 



Attitude is of very real importance in producing 

 mimetic resemblance, and living specimens often appear 

 mimetic when in the cabinet they do not. So that the 

 ignorant remark, which may sometimes be seen in 

 print, that mimicry is the product of the imagination 

 of an '* arm-chair philosopher " need not be seriously 

 considered. 



One day, on Damba Island, I was looking at a nest 

 of the tree ant, jEcophylla, among the leaves of a bush. 

 This species, by means of silk spun by a larva held for 

 the purpose by an ant, fastens together leaves to make 

 a more or less globula>r nest about the size of a cocoanut. 

 Wishing to obtain a few specimens I proceeded to box 

 them, when, to my great astonishment, one of them 

 jumped, thus revealing itself to be no ant, but a mimetic 

 spider, 2 which had been running about unperceived 

 among the ants ! 



The wonderful thing about this case is the great 

 anatomical difference between ant and spider, both 

 internal and external. The model has head, thorax, 

 and abdomen separated from each other by well marked 

 constrictions, but the spider has head and thorax fused 

 into a cephalo-thoracic mass, separated from the abdomen. 

 The ant has three pairs of legs, the spider four ; the ant 

 has a pair of long mobile antennae, the spider none. 

 Diagrammatically the difference is shown overleaf. 



* Poulton, Essays on Evolution, p. 239. 



2 Myrmarachne Joenissex. Another spider mimic of the same model is 

 described and figured by Shelford in A Naturalist in Borneo, pp. 230-1. 



