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

Abstract

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.

Starvation drives a threshold triggering communication

“…In social insects, it is known that the number of individuals participating in food recruitment increases with starvation (Cosens and Toussaint, 1986;Hölldobler, 1971;Howard and Tschinkel, 1980;Howard and Tschinkel, 1981;Josens and Roces, 2000;Roces and Hölldobler, 1996;Seeley, 1995;Traniello, 1977;Wallis, 1962;Wallis, 1964). Our work shows that this phenomenon does not result from an increase in individual trail marking.…”

“…aphid colonies composed of highly productive individuals), the food volume ingested by foragers and hence the amount of food retrieved to nest increases. Such an increase of retrieved food quantities has been reported for many ant species (Cosens and Toussaint, 1986;Howard and Tschinkel, 1980;Howard and Tschinkel, 1981;Josens and Roces, 2000;Wallis, 1964). Likewise, honeybee foragers counter depletion of pollen stores by increasing pollen load size per forager (for a review, see Seeley, 1995).…”

“…As the year goes by, some aphid colonies spread out and offer huge amounts of honeydew while others disappear abruptly, or steeply change their honeydew production according to the weather conditions. Due to the high variability of honeydew amount, aphid-tending ants have to undergo long periods of starvation (Cosens and Toussaint, 1986;Skinner, 1980) that force them to intensify their food retrieving activities and transport more food (Cosens and Toussaint, 1986;Howard and Tschinkel, 1980;Howard and Tschinkel, 1981;Josens and Roces, 2000;Seeley, 1995;Wallis, 1962;Wallis, 1964). A wide range of explanations have been given for such strategy choice, among which many are considered merely to be cost-benefit problems that foraging animals must solve while the assessment mechanisms of all information are often considered as a black box (Giraldeau and Caraco, 2000).…”

“…Among all these variables, starvation level is one of most important parameters affecting collective foraging behaviour in ants (Cassill and Tschinkel, 1995;Cosens and Toussaint, 1986;Hölldobler, 1971;Roces and Hölldobler, 1996;Traniello, 1977), honeybees (Seeley, 1995;Schulz et al, 1998;Schulz et al, 2002; and bumble bees (Cartar and Dill, 1990). Aphidtending ant species, such as Lasius niger, are good biological models to study the behavioural flexibility of animals faced with fluctuations of nutritional supplies.…”

Carbohydrate regulation in relation to colony growth in ants

“…Smaller meal sizes on dilute than concentrated sugar solutions in fooddeprived insects is well known (Dethier, 1976;Bernays and Simpson, 1982), including in social insects (Balderrama et al, 1992;Josens et al, 1998;Moffatt and Nunez, 1997;Nunez, 1966;Nunez and Giurfa, 1996;Pflumm, 1969). However, by the second day, colonies fed with dilute solution had not only increased the numbers recruited to the food site, but also individual ants were collecting larger loads: a result previously shown in Formica aquilonia ants (Cosens and Toussaint, 1986) and Camponotus mus (Josens and Roces, 2000), as well as in blowflies (Simpson et al, 1989). By contrast, the crop loads of ants fed with concentrated solution declined significantly throughout the week (Fig.·7).…”