Chap. Y. 
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 
