3 
1891.] J. H. Tall Walsh — On certain Spiders which mimic Ants. 
tennse which are generally kept in motion as the little animal runs 
along. In adapting themselves to circumstances, the spiders have 
learned to use their first pair of legs to represent antenna;. In all the 
cases that I have noticed, the spider when moving holds its first pair of 
legs aloft to simulate antenna;, and certainly in the case of a Salticus 
(sp. F) which mimics Oamponotus micans Mayr these legs are kept in 
continual motion. On one of the bottles presented to me by Mr. J . 
Wood-Mason I find the following note made at the time the spiders were 
captured : — 
“ (Oachar, J. W.-M.) smaller one mimics and runs about with a 
little brown ant carrying its palpi like the open mandibles of the ants, 
and its first pair of legs off the ground and elbowed, as the ants do their 
antennae.” 
This note draws attention to another curious resemblance which 
is produced by the flattening of the terminal joint of the palpi. 
In the spider found by Mr. Wood- Mason and in several other species, 
this formation occurs and the falces, which are small, are partly hidden 
by the palpi. In other species and notably in Salticus formicarins the 
palpi are small and the resemblance to mandibles is produced by the 
large flattened first joint of the falces ; thus the same end, as far as the 
resulting mimicry is concerned, is attained by two very different mor- 
phological variations. Belt (Z. c.) notices the fact that in the Nicaraguan 
species the fore-legs are raised from the ground and J. P. Mansel Weale 
(Z. c.) makes some interesting remarks which I will quote. He says : — • 
“ The most perfect cases of mimicry I know of are two spiders 
(specific nature unknown to me) which have the closest resemblance to 
ants. They belong to the Salticidce and are apparently related to Salticus 
formicarins. The one is smooth black and shining and runs rapidly on 
the ground and bark of trees, and resembles the ant which builds its 
nest in Acacia horrida and is used by the Kafirs for the purposes of 
torture. The other is larger and has its cephalothorax dull black and 
its abdomen covered with short yellowish hairs. It is generally found 
running on the stems of herbaceous plants and small bushes and closely 
resembles an ant found in similar situations. The fore-legs in both 
species are larger than the second pair are frequently held up when 
they closely resemble the antennas of ants.” 
As a general rule therefore most observers agree that the first 
pair of legs is used to simulate antennae, but an exception must be noted. 
E. G-. Peckham (l. c.) records that an American species Synageles 
picata “ holds up its second pair of legs to represent antennae.” This 
peculiarity of habit has appai'ently produced or been produced by a 
change in the relative length of the legs in this species. The general 
