The dynamic nature of the activities of the wood ant Formica aquilonia foraging to static food resources within a laboratory habitat

ABSTRACT. A laboratory colony of the wood ant Formica aquilonia (Yarrow) was maintained under strictly controlled feeding regimens. The number of foragers at a particular site is related to the previous provisioning of the colony and the familiarity and accessibility of the resource to foragers. Under a standard regimen a predictable number of ants forage to a known site and display a typical pattern of daily activity. This pattern is examined under stable and changing circumstances. Following food-deprivation individuals increase their foray-frequency and carry larger volumes of sugar solution per foray. On days of critical food-deficit supernumerary workers are recruited. How foragers are directed to a novel food source in unfamiliar territory is examined. Following-behaviour is not involved, neither it appears are pheromones.     

Plant‐mediated effects of soil nitrogen enrichment on a chemically defended specialist herbivore,Calophasia lunula

1. Nitrogen enrichment is an important driver of environmental change. In the present study, plant‐mediated effects of increased nitrogen on a specialist herbivore, Calophasia lunula Hufnagel, which sequesters antirrhinoside, an iridoid glycoside produced by its host plants, were examined. 2. Caterpillars were reared on Linaria dalmatica plants grown under low or high N treatments, and C. lunula performance traits and antirrhinoside levels were measured. Additionally, a bioassay was conducted with predatory ants to examine their response to antirrhinoside. 3. Nitrogen enrichment increased larval biomass and decreased larval antirrhinoside concentrations, but had no effect on plant iridoid glycoside concentrations or larval antirrhinoside content. Thus, differences in larval antirrhinoside concentrations were evidently a consequence of increased larval biomass. Additionally, nitrogen treatment had no effects on pupal performance or defence traits. 4. Bioassay results demonstrated a deterrent effect of antirrhinoside, but additional tests are necessary to evaluate the defensive role of this compound in insects. 5. Surprisingly, this study demonstrated little effect of a six‐fold increase in nitrogen availability on L. dalmatica iridoid glycoside concentrations or sequestration by C. lunula. Moreover, the results suggested that changes in plant primary chemistry were more important than secondary chemistry for this specialist herbivore, and that some insects may be insensitive to N enrichment.     

Circadian rhythm of locomotor activity in individual workers of the wood ant Formica rufa

ABSTRACT. Individual worker ants isolated in an actograph exhibit circadian rhythms of locomotor activity. Entrainment occurs more readily in LD 18:6 h than in LD 12:12 h. The ants are either light-active or dark-active. Phase angle and duration of activity is influenced by photoperiod.