Page 38 - Engineering in Nature

Engineering in Nature

• When Gathering Time Comes
Insects give off "gathering" pheromones when they rest, and all the
individual members of the species come together. These pheromones
allow insects such as bees, ants and termites to live together.
Among shelled insects of species Ipidae and Scolytidae, individuals

fortunate enough to find a tree trunk suited to feeding and egg-laying
secrete off a pheromone, causing all the members of the colony to
gather together. 12
Fire ants drag their stings along behind them, leaving a scent trail
for the members of the colony to follow. J. H. Tumlinson, at the U.S.
Department of Agriculture's Research Service Laboratories in
Gainesville, Florida, estimated that 1 milligram of this substance
could lead a column of ants around the world three times! 13
Considering this precise effect that pheromones have, one can im-
mediately see just how important they are for insects. Particularly in
times of danger, the slightest defect in this communications system
could have devastating consequences. The pheromones given off at
such times sound the alarm through the entire colony.
Alarm pheromones, which evaporate and have short-lived effects,
are the same in many species. When danger approaches, ants emit
pheromones from glands in the hind parts of their bodies, bees from
glands in their stings, and other insects from glands in their mouth
parts. Ants emit the alarm pheromone in order to muster together for

attack purposes. The pheromone's scent brings the members of the
colony together and allows many individuals to take part in a united
defense.
For example, when some species of leaf mite are attacked by larger
insects, they give off an alarm pheromone that warns other individu-
als feeding nearby to move away. Leaf mites detect these chemical se-

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