Chap. V. PARASITIC FLIES. 365 



by step, under the protection of these covered passages, 

 through the thickets, and on reaching a rotting log, or 

 other promising hunting-ground, pour into the crevices 

 in search of booty. I have traced their arcades, occa- 

 sionally, for a distance of one or two hundred yards ; 

 the grains of earth are taken from the soil over which 

 the column is passing, and are fitted together without 

 cement. It is this last-mentioned feature that dis- 

 tinguishes them from the similar covered roads made 

 by Termites, who use their glutinous saliva to cement 

 the grains together. The blind Ecitons, working in 

 numbers, build up simultaneously the sides of their 

 convex arcades, and contrive, in a surprising manner, 

 to approximate them and fit in the key-stones without 

 letting the loose uncemented structure fall to pieces. 

 There was a very clear division of labour between the 

 two classes of neuters in these blind species. The large- 

 headed class, although not possessing monstrously- 

 lengthened jaws like the worker-majors in E. hamata 

 and E. drepanophora, are rigidly defined in structure 

 from the small-headed class, and act as soldiers, de- 

 fending the working community (like soldier Termites) 

 against all comers. Whenever I made a breach in one 

 of their covered ways, all the ants underneath were 

 set in commotion, but the worker-minors remained 

 behind to repair the damage, whilst the large-heads 

 issued forth in a most menacing manner, rearing their 

 heads and snapping their jaws with an expression of 

 the fiercest rage and defiance. 



The armies of all Ecitons are accompanied by small 

 swarms of a kind of two-winged fly, the females of 



