Trail-laying and recruitment to sugary foods by foraging red wood-ants Formica aquilonia Yarrow (Hymenoptera: Formicidae).

The use of trail communication by red wood-ants, Formica aquilonia Yarrow, foraging to sugar baits, was investigated by providing a laboratory colony with aqueous sucrose at two novel feeding sites, with a third site, providing no food, as a control. During trials, the sites were connected to the nest by paper bridges which were replaced between treals. One of the sites providing food was reached by a two-way bridge, as was the control. The second baited site was reached by a one-way bridge: this site had a one-way exit from which returning foragers dropped to the nest. Hence, if returning foragers laid a trail from a bait, they would do so on the two-way bridge, but not on the one-way bridge by which foragers did not return, nor on the bridge to the unbaited site. This would lead to a greater increase in foraging traffic on the two-way bridge, relative to that on the other two bridges, during a given trial. Each trial was preceded by a 30-min counting session with no baits present, to establish the mean number of ants arriving per minute on each bridge through random exploration. After provision of food, ants arriving on each bridge per minute were counted in four separate 30-min sessions: each count was then converted to a proportion of the original mean traffic on that bridge, and the change in traffic with time was compared between bridges using analysis of variance. The increase in traffic was significantly greater on the two-way bridge than on the control and one-way bridges, indicating that replete ants returning from the bait left a trail on the homeward route, which other ants subsequently followed.