Published online by Cambridge University Press: 05 June 2016
Wood ants are almost unique among insects in having a largely predictable and easily visible pattern of foraging. This is the result of their mutualistic interaction with tree-dwelling aphids and other sap-sucking insects, requiring foragers to travel regularly between the wood ant nest and persistent feeding sites where they collect honeydew from their mutualists. Collected honeydew, and also prey, are shared with nestmates back at the nest; this broadly follows a ‘central-place foraging’ model. Wood ants forage predominately on tree trunks and in tree canopies. The success of wood ants is due, in part, to their highly effective foraging strategy: workers dominate a territory and the food resources in it. For these reasons, foraging behaviour has been a major theme in wood ant research over recent decades.
This chapter reviews the wood ant diet including the mutualism with aphids and other insects, and explores the consequences of this mutualism for host trees and other invertebrates. As in most social insects, only workers forage, but among workers there are further distinctions as to who forages, when they forage, and how they navigate between nest and foraging site. How resources are exploited and transported within wood ant territories, especially for polydomous colonies, provides an insight into how decentralised networks can function efficiently, making wood ants a good case study for transportation networks more generally.
Wood ant diet
Wood ants are omnivorous, thus they practically eat ‘everything’. Generally, two main sources form their diet: honeydew is used mainly as energy for metabolic maintenance, whereas insect prey and scavenged material is used to provide protein for rearing the brood (Lange 1960). In addition, minor contributions are made by the collection of seeds and the consumption of tree sap and berry juices (Wellenstein 1952; Rosengren and Sundström 1991; Otto 2005).
Honeydew forms the largest component of the wood ant diet, estimated as contributing between 62% (Wellenstein 1952) and 94% (Rosengren and Sundström 1991) of food brought into a nest (Figure 7.1). Estimates of the quantity of honeydew collected annually per wood ant nest vary greatly depending on ant species and location, and presumably also on the study methods.
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