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Silk Ant Discovered in Pincushion
|Brian L. Fisher - South African Museum
the Nardouw Mountains, 23 km NE of Clanwilliam, we
discovered silk-producing ants, Melissotarsus emeryi
Forel, nesting in live wood of Ls praemorsum!
This is the first time silk production has been
recorded in adult ants. It is also the first record of
silk production at any life stage in the subfamily
A loose network of silken material lines the gallery
tunnels and is combined with wood particles to seal
cracks in tunnel walls and to close exit holes. The silk
is produced by adult workers from glands located below
the head at the base of the mandibles. The ants apply the
silk using their modified front legs, or "silk
To seal gaps in the tunnel, the ant takes a wood
fragment in her mandibles and draws silk out of the silk
glands by lifting the forelegs alternately in a kneading
fashion ("spinning"). The silk fibres are
applied to the opening and wood fragment with the silk
brush. When sufficient silk is applied, the wood fragment
is pushed with the forelegs, forcing it out of the mouth
into the gap. Spinning continues until the wood fragment
forms part of the tunnel wall.
||The entire feeding area is also sealed
with silk. Workers are never seen wandering outside their
tunnels, not even to visit the extrafloral nectaries on
the leaves. If they fall out of the galleries, the
workers move awkwardly and have difficulty in turning
themselves off their backs. This is because the second
and third coxae are massively developed: the second being
distinctly the largest, and appears to limit leg movement
outside the tunnels. The ants are thus unique in walking
with the middle pair of legs pointing upwards in contact
with the tunnel roof, but this means they cannot walk
except in the tunnels.
In addition, these ants farm a
strange scale-insect inside the tunnels. Other ants farm
scale-insects that produce honey-dew, but these
scale-insects produces wax! Ants cannot live on wax (or
so we thought).
This Silk Ant is an anomaly. It possesses a peculiar
morphology, nesting behaviour, manner of walking, and the unique
capacity among adult workers of producing silk. The big question
is why it produces silk? The production of silk may allow the
silk ant to make use of the living wood habitat in a way not
possible by other ant species, but at the cost of not being able
to live outside of their tunnels.
Does the Silk Ant occur throughout the range of Ls praemorsum?
Does it occur on the Pincushions? Look for the silk in the wood
cracks, and crack open some dead wood to confirm their presence -
the ants should not be able to "get up". Please send
your observations to us!
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