THE ENTOMOLOGIST. 279 



behind. Eyes ovate, slightly prominent, placed forward on 

 the sides of the bead. Mandibles riifo-piceous, large, stout, 

 triangular, strongly dentated with two large and several small 

 teeth at their inner border, deeply punctured above, and 

 covered thinly with short yellow silky liairs. Anteimse vnfo- 

 piceou.s ; scape shorter than the head ; flagellum thick, cla- 

 vate. Thorax rounded before, with a tubercle above ; the 

 meso- and metathorax flattened laterally, and having a deep 

 strangulation between them. Scale of the peduncle very 

 large, ovate, and pointed above. Abdomen ovate, the apical 

 margin of its segments piceous. Legs of moderate length. 

 Tarsi fuscous. The joints of the tarsi and antennae fringed 

 with yellow silky hairs. 



These small ants are far from being the least remarkable 

 species I collected. Their nest is made underground, and 

 occasionally in the substance of hard sandstone ; sometimes 

 in cracks and fissures of the rock : they appear to bore the 

 sandstone with ease. They emit a very strong smell of 

 formic acid when distiu-bed ; but the most peculiar instinct 

 possessed by these insects is that of always marching to and 

 from their nest in dense regular files, like the foraging parlies 

 of predatory Ecitons in South America : however far these 

 insects wander, a compact line of them may always be traced 

 back to the nest : so regular are their tracts that I have fre- 

 quently found the sandstone slightly grooved by them. I 

 have been led to the belief that this wonderful instinct has 

 been given them to protect them from the ravages of the pre- 

 datory Alyrmecias and Myrmicas, which ai*e so abundant in 

 the same localities. On the 31st of October, observing several 

 individuals of M^'rmecia gulosa carrying Formica purpurea 

 in their huge jaws, I watched them carefully, and found that 

 the great iMyrmecias, four times the size of the Formica at 

 least, feared the latter in open ground, and laid in wait for 

 them on the outskirts of their nest, until they got an oppor- 

 tunity to slip out and seize one that had been unwary enough 

 to stray from its companions into the vicinity of its great 

 enemies' ambush. Had these insects the same instinct as 

 their little congeners they would escape the danger. I 

 always found that two or three individuals of Formica pur- 

 purea or Smithii put to flight the largest Myrmecias. 



Jl. F. riifonigra, Lowne. — Worker 1^ line long, rufo- 



