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Feeding in Ants
The majority of ants are general predators or scavengers, feeding on a wide range of prey including other arthropods and seeds.
Adult ants feed exclusively on liquid foods. They collect these liquids from their prey or while tending Hemiptera and other insects. Solid prey, that which is most often seen being carried by workers, is generally intended as food for larvae. Adults which remain in the nest, including the queen, receive much or all of their food directly from returning foragers in a process called trophallaxis. During foraging, workers collect fluids which are stored in the upper part of their digestive system (the crop). Upon returning to the nest, these workers regurgitate a portion of this stored fluid and pass it on to other workers. In some extreme species, this fluid is transferred to special workers, called repletes or honey ants, which remain permanently in the nest and act as living storage vessels. They store food when available and distribute it to the colony in times of shortage.
While most ants will feed on a wide variety of foods, others specialise on a much narrower range. A number of species, especially those in the genera Pyramica and Strumigenys, show a strong preference for Collembola. Others (for example species of Discothyrea) prefer the eggs of assorted arthropods. Still others (especially Cerapachys and Sphinctomyrmex) raid the nests of other ants to capture their larvae and pupae. Many of the groups with specialised feeding requirements also possess unusual morphological adaptations. For example, the mandibles in some of the highly predacious groups are much elongated and are armed with large teeth, especially at their tips (these include Anochetus, Epopostruma, Odontomachus, Orectognathus, some Pyramica and Strumigenys).
The seeds of many plants have special food bodies (called elaiosomes) which are attractive to ants. Ants collect these seeds, eat the food body and sometimes the seed as well. However, many of the seeds remain intact after the food body is removed and are often placed within the ants’ nest or on their midden piles where they later germinate. It is believed that seeds collected by ants have a higher chance of germinating and surviving when compared with seeds which are not collected. This is because they are less likely to be attacked by seed predators and because they are often placed in sheltered locations near the ants’ nutrient-rich refuse piles.
In general, ants show a preference for foraging either during the day or at night. In some groups foraging will occur both during the day and at night, although there may be peaks of activity with fewer foragers active during other periods. In the arid zone, the foraging activities of many species are highly dependent on temperature. Some species (for example most Tetramorium and some larger Rhytidoponera) are only active during the cool morning and evening hours, while others are active only during the hottest parts of the day (members of Melophorus). On cool or heavily overcast days, species which are normally only seen at night may be active during the day while high-temperature loving species may remain in their nests all day.
Sugar ants (Camponotus) tending homopterans to collect honeydew. Photo by Steve Shattuck.
A Camponotus consobrinus worker returns to her nest after collecting honeydew high in a tree, her gaster extended with food for her sisters. Photo by Steve Shattuck.
A Camponotus worker carries a seed with an elaiosome back to her nest. The elaiosome will be consumed by the ants while the seed will be discarded.
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