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Marvels of the Universe 



MIMICRY IX SPIDERS 



BY R. I. POCOCK, F.R.S. 



Many insects, as well as other animals, are protected from enemies by some quality such as a hard 

 shell, a nast}' taste or a repulsive smell which makes them unpalatable. After a certain amount 



of experience, varying in ex- 

 tent according to the species 

 and individual, insectivorous 

 birds and mammals learn to 

 know these uneatable species 

 by sight, and thereafter leave 

 them unmolested. Clearly, 

 therefore, a tasteful species 

 \\dll be greatly benefited if it 

 resembles a distasteful one 

 sufficientl}' closely to deceive 

 its enemies. Resemblances of 

 this kind are very common in 

 Nature, and the phenomenon 

 is called " mimicry." 



Now the majority of spiders 

 are comparatively defenceless, 

 and being highly palatable are 

 extensively preyed upon by 

 other animals. But the worst 

 enemies they have to fear are 

 the digger or mason wasps 

 which, to feed their larvje, 

 store away in their burrows 

 and mud-cells vast numbers 

 of spiders, stung to a state of 

 coma and so preserved against 

 decay. Persecution by many 

 enemies, and especially by 

 these wasps, has reacted upon 

 the instincts and structure of 

 spiders in various wonderful 

 ways, perhaps the most won- 

 derful being the mimetic re- 

 semblance it has brought about 

 between some of them and 

 protected insects, more par- 

 ticularly those that the mason 

 wasps do not attack. There 

 are indeed one or two instances 

 known of spiders accurately 

 mimicking small snails which 

 are useless food for wasp-larvae and are neglected by small insectivorous birds. Other spiders for 

 the same purpose imitate in colour and shape little shining hard-shelled beetles. Others, again, 



Ifiil J. IVlleulmni. 

 SPIDER MIMICR\'. 



The two spiders shown on the left are South-American species that both mimic 

 one Ant. in order to protect themselves from the attacU of a Mason-wasp that stores 

 up Spiders for the food of its grubs, but leaves Ants alone. The Ant mimicked is 

 shown on the right. 



