Social insects (bees, wasps, ants, and termites) utilize an array of pheromones
to maintain the high level of organization in their colonies. Many
species of ants and termites that are essentially wingless lay terrestrial odor
trails leading to food sources or nesting sites. According to Wilson (1971), the
odor trail system is the most elaborate of all the known forms of chemical
communication. Sudd (1959) has defined trail laying as a field activity in
* Present address : Institute for Organic Chemistry 11, University of Erlangen-Numberg,
Erlangen, West Germany.
which an insect marks a route with scent or odor traces such that other
insects of the same community are able to follow it. Essentially, a foraging
worker returning from a food source lays a more or less continuous narrow
band of chemicals on the substratum as it returns to the nest (“recruitment
trails”); these trails may excite other workers to follow the chemical scent to
the food, where they in turn feed and, as they return to the nest, reinforce the
chemical deposit. Workers returning from visiting an exhausted food source
do not reinforce the trail, so that eventually it evaporates and the signal is
obliterated. The ants can regulate the amount of trail substance they lay on a
trail (Hangartner, 1970). Short-range trail pheromones, laid with footprints
in the vicinity of the hive or nest, are also known for bees and wasps (Butler et
al., 1969; Lindauer and Kerr, 1958). Trail pheromones can also facilitate
migration of the colony to a new site (“emigration trails”). Some long-lasting
trails may serve as chemical cues in home range orientation and help in
marking home territories.