THE CAUSE OP MIMETIC RESEMBLANCE. 



589 



sometimes crosses the cephalothorax, sometimes the abdomen. 

 The absence of antennae in the spider is known to be compen- 

 sated in some of the species, which have been studied in the 

 living state, by the habit of holding up one pair of legs, while the 

 walking legs are thus reduced to the ant-like number of six. Of 

 two well-known North A.meriean species, Synageles picata holds 

 up the second pair, and Synemosyna formica the first. The habits 

 of seizing and dealing with prey, aud the movements generally 

 are extremely un-spider-like aud most suggestive of ants ; so 

 that the nervous and muscular systems, as well as the body- 

 form, have been modified. The remarkably ant-like appear- 

 ance of these two species is shown in the adjoining fio-. 1 (A 

 and B). 



Fig. 1. 



Pig. 2. 



-Fig. 1- — Two North-American Afctid spiders which resemble ants. A is Synageles 

 picata,; B, Synemosyna formica. (From Gr. W. and E. G-. Peckham, 

 Occasional Papers of the Nat. Hist. Soc. of Wisconsin, vol. i. 1889, 

 pp. 110 & 112.) 



Fig. 2 (x 3).— The young larva of Stauropus fagi seen from above and fj-om 

 the left side. 



Among the Insecta, too, there are many examples of an ant-like 

 appearance brought about by changes of the same kind as those 

 mentioned above, although less marked because the forms 

 to be approximated are less essentially difiierent. Among the 

 Lepidoptera the young larvge of a British moth, Sfauropusjagi. 

 have often been described as resembling ants. The likeness has 

 recently been analysed in much detail by Portschinski (" Colo- 

 ration marquante et Taches ocellees," V. : St. Petersburg, 1897, 

 p. 44). This acute observer considers that the head of the 



LINX. JOtTEN. ZOOLOGY, VOL. 2XYI. 42 



