4 PECKHAM. [Vol. 2, 



usuall}' browns and blacks with white bands, and sometimes 

 with orange or red, Uke that seen in ants ; and there is a close 

 similarity in general appearance, so that the determination of 

 genera and species is rendered very difficnlt. 



The palpi of the males are not especially variable. In 

 some species, notably in those of Salticus, the tarsus of the 

 palpus is palette-shaped in both sexes. In certain species of 

 Synemosyna the front end of the venter has a hard plate, ex- 

 tending from pedicle to epigynum ; and sometimes the integu- 

 ment is also more or less hardened on the upper surface of the 

 abdomen. 



The ant-like Attidse are usually small, averaging about 

 4 mm. in length, although we have one species which 

 reaches 11 mm. They are commonly found running on 

 plants and bushes, or on the ground in hot, stony places. They 

 are like other Attidis in spinning no snares. Synageles 

 picata, which we kept in confinement, made a little, tubular 

 nest, into which it retired during the colder parts of the da,j. 



The few species that we know in life mimic the move- 

 ments as well as the form and color of ants.* Of one of these 

 species we have said in a former paper : " While picata is ant- 

 like in form and color, by far the most deceptive thing about 

 it is the way in which it moves. It does not jump like the 

 other Attidte, nor does it walk in a straight line, but zig-zags 

 continuall}^ from side to side, exactly like an ant which is out 

 in search of booty. This is another illustration of what 

 Wallace has shown in relation to butterflies — that that which 

 is an important functional structure in the mimicked group 

 may be imitated by the mimetic species, even when the habits 

 of the latter render it perfectly useless. The ant only moves 

 in this way when it is hunting ; at other times it goes in a 

 straight line ; but its little imitator zig-zags always. 



" In addition to its ant-like walk, picata holds up its second 

 pair of legs in such a way that they look like antennse. 



*AccorcIing to other observers this is true also of Central American and African 

 species. See Bett's Naturalist in Nicaragua, p. 314, and J. P. M. Weale in Nature, 1871, 

 Vol. III., p. 508. 



