Individual decisions and communication in foraging by red wood-ants Formica aquilonia Yarrow (Hymenoptera: Formicidae)
Three colonies of red wood-ants Formica aquilonia were maintained in the laboratory on Tenebrio larvae and aqueous sucrose solution (7&'37 w/v). The laboratory was artificially lighted for 14hrs/day between August and April; the temperature was kept above 5°C. The foragers of each colony obtained sucrose from two sites to which the food was delivered at defined rates: flow rates to paired sites were in the ratios 1:1, 2:1 and 3:1. The foragers approximated to the ideal free distribution between sites. Colour-marking showed that certain individuals foraged at a preferred site: other ants moved to whichever site provided the better feeding rate. Further colour-marking showed that foragers become faithful to a site soon after discovering it; their fidelity does not increase with use of the site. Recruitment to food in Formica aquilonia was investigated: no recruitment was observed when ants discovered 7% w/v aqueous sucrose, but foragers which discovered 28&'37 w/v sucrose solution, provided after the colony was without sucrose for a day, laid chemical trails on returning to the nest. Food was provided at two novel sites, each connected to the nest by a paper bridge. In one case, foragers used the same bridge to travel to and from the site; in the other, they arrived via the bridge, but returned by a separate, one-way route. Traffic increased more with time on the two-way than on the one-way bridge, implying that returning repletes left a trail on the homeward route, probably of hind-gut fluid, which other ants subsequently followed. Formica aquilonia foragers may exchange information during contact. Most ants which were contacted by a replete forager did not subsequently go to a feeding site, but when they did so they tended to select the site used by the replete.