Fungi that influence ant behavior....

Preferred Customer MCSpear at
Fri Jan 31 23:55:45 EST 1997

In studies using Metarhizium to kill cockroaches an acquaintance discovered
that there are behaviors hard wired into the roaches to minimize epidemics
in the "colony".  Basically it seemed like the sick roaches were inclined
to get away from their fellows and into an open area to die.  Presumably
this was to keep the inoculum load down for their non-infected brethren.

This actually killed an environmentally friendly and very effective roach
croaker.  The housewife would come into her kitchen in the morning to find
the floor populated by more moldy morbid roaches than she would care to
admit could live in her house.  From her perspective the fungus treatment
increased the number of roaches she saw in her house therefore it was

In related work a very effective agent was developed to kill fire ants.  As
the ant-hill became sick the healthy ants would bolt and make a new hill
with about 30% of the remaining population.  You could dispatch the colony
only be repeatedly finding the off-shoot colonies and treating them.

The moral of the story is that there are an number of known examples where
insects have pre-programmed responses to fungal infection.  It does not
seem to tough to believe that sick ants would try to exclude themselves
from the colony and that over time this behavior could be used by a fungus
to help dissemination.  Just another case of the pathogen-host arms race.

    ---- Mark

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