Harvesting Ants and Trap-Door Spiders: Notes and Observations on Their Habits and DwellingsMoggridge, John Traherne
Science
Harvesting Ants and Trap-Door Spiders: Notes and Observations on Their Habits and Dwellings
Moggridge, John Traherne
Ants; Trap-door spiders
In the nests of _Nemesia meridionalis_ the tube, instead of being
simple, as it is in all other known nests, is invariably branched,
a second tube joining the first at the point where the lower door
is hung and forming with it an angle of about 45°. The main tube
descends and is frequently curved, or sometimes doubly bent like the
spout of a tea-kettle (A, Plate X. p. 100), while the branch ascends,
and in some few instances reaches the surface, though it is usually a
_cul de sac_ (Plate IX.)
[Illustration: _Plate IX._]
In the exceptional cases where the nests have two superficial
openings, one of the two surface doors always appears neglected and
going to decay, or is covered with earth which chokes the upper part
of its tube. The explanation of this probably is that the spider
found the original entrance blocked up or in some way unfitted for
use, and then prolonged what was the blind branch until it reached
the surface and replaced the former doorway. However this may be it
is certain that in the great majority of nests it will be found that
the branch ends in the earth, and is a _cul de sac_, and this I have
invariably observed to be the case in the nests of very young spiders
of this species (fig. B, Plate IX.)
The tube is frequently enlarged at the mouth, and forms a spreading
lip which the surface door is usually large enough to cover (A 1,
Plate IX.)
In these branched double-door nests the upper door does not fit into,
but merely lies upon, the mouth of the tube, the elasticity of the
hinge and its own weight being sufficient to keep it closed. The
lower door is suspended by a hinge placed at the apex of the angle
formed by the bifurcation of the tube, and is hung in such a manner
that it can either be pushed upwards so as to lie diagonally across
and block the main tube, or be drawn back so as to fit into and close
the entrance to the branch.
This will, I think, best be understood by reference to the drawings
of a small nest of this type given at B 1 and B 2 in Plate XI. p.
105, where the second door is shown in its two positions. This lower
door is from 1 to 1-1/2 lines thick, channeled above, but nearly
flat on the back, and of an elliptic form, with a loose appendage
at its lower end, the whole being made of earth enclosed in a case
of silk.[66] When the lower door is drawn back so as to close and
conceal the entrance to the branch, it lies in the same plane, and
closely corresponds in curvature with the lining of the main tube and
almost appears to form part of it (fig. A, Plate X. p. 100, and fig.
B 1, Plate XI. p. 105).
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