No. 2.] PROTECTIVE RESEMBLANCES IN SPIDERS. 103 



of defense against the enemies of both. This defense may 

 consist of a disagreeable taste or odor, as in the Hehconidse, 

 which are mimicked by other butterflies; of some special 

 weapon of offense, as where wasps and bees ai'e mimicked 

 by flies and moths, or posionous vipers by harmless caterpillars; 

 or of a hard shell, as where the coriaceous beetles are 

 mimicked by those that are soft-bodied. 



Instances of this rule are exceedingly numerous ; indeed, 

 Wallace says that specially protected forms are always mim- 

 icked ; still we have nothing mimicking our Gasteracanthidse. 



Class 2. The mimetic may prey upon the mimicked spe- 

 cies, its disguise enabling it to gain a near approach to its vic- 

 tims ; as the mantis, mentioned by Bates as exactly resembling 

 the white ants upon which it feeds ; and the flies which mimic 

 bees, upon which they are parasitic, and are thus able to enter 

 the nests of the bees and lay eggs on the larvas. 



Class 3. The mimetic species may, by its imitation, be pro- 

 tected from the attacks of the creature it mimics, as is the case 

 with the crickets and grasshoppers which mimic their deadly 

 foe, the hunter wasp. 



Class 4. The mimetic species may prey upon some crea- 

 ture which is found commonlj^ with and is not eaten b}^ 

 the mimicked species. 



No two of these classes are mutually destructive so that in 

 any case of mimicry a double advantage may be gained. 



Let us see which of these advantages has directed the 

 development of mimetic tendencies among spiders. 



While among beetles and butterflies we most commonly 

 find mimicry of one species by another within the same order, 

 we have no instance of a spider mimicking another spider.* 

 This may be accounted for by the fact that the specially 

 protected spiders depend for their safety upon the possession of 

 hard plates and spinous processes, and although the hardened 

 epidermis might be imitated (we know that hard-shelled beetles 



* The spiders Instanced by Pavesl (toe. cit.,-p. 7) which resemble other genera 

 rather than their own, such as Nephita tetragnatJwides, Tetragnatlia epeiridex, etc., 

 cannot, it seems to me, be classed properly under mimicry. 



