ANT-LIKE SPIDERS OF THE FAMILY ATTID.E. 



GEORGE W. AND ELIZABETH G. PECKHAM. 



Introduction. 

 In the familjr Attidse, as in several other famihes of 

 Arachnida, there is a group of spiders whose members are 

 remarkable for their resemblance to ants. Some of the species 

 of this group are found in the sub-family Attinse (Attidfe hav- 

 ing the eyes arranged in three rows), and some in the sub-fam- 

 ily Lyssomanse (Attidte having the eyes arranged in four rows). 

 In many cases the likeness to ants is rendered striking by 

 a constriction of the cephalothorax or of the abdomen, by 

 which the body seems to be made up of three segments instead 

 of two. Sometimes both cephalothorax and abdomen are con- 

 stricted. Of all the American Attidse Synemosyna formica is 

 the most ant-like ;* and it would seem that in this genus 

 the differentiation toward an ant-like form has reached its 

 highest point. 



The leg formula in the ant-like Attidee varies but slightly. 

 The fourth pair is almost always the longest, but in a few cases 

 the first is longer than the fourth. The legs are usually 

 slender, without much difference in size ; occasionallj' the first 

 pair is thickened, and less often, the second. 



There is much less diversity in color in this group than 

 in other Attidse, and there is also less difference between the 

 sexes, although in the males of some species the integument is 

 more iridescent and the first legs are larger than in the 

 females ; and in some genera, as Salticus and Paradamoetas, it 

 is common for the males to have long, horizontal falces, while 

 those of the females are short and vertical. The colors are 



*0f this species Hentz (Spiders of the United States, p. 73) says : " I had seen indi- 

 viduals of this species running on the blades of grass and stems of weeds long before I 

 distinguished them from ants. They move with agility and can leap, but their habitus is 

 totally different from Attus. They move by a regular progression or regular Avalk, very 

 dift'erent from the halting gait of the sub-genus." In a former paper we stated that 

 Synemosyna formica, like Synageles picata, holds up its second pair of lees to look like 

 antennae. This is an error. It is with the first, not the second, pair of legs that formica 

 mimics the antennjc of ants. 



