Repletes

All ants store fluids, collected while foraging, within their crops (located within their gasters). In most cases these fluids are consumed by the foraging worker herself, as well as being shared with her sisters within their nest after returning from a foraging trip. In these cases the workers gaster will expand slightly during foraging but return to normal size within a short perod of time as the fluids are consumed or passed to other workers. However, in some species this fluid is transferred to special workers in the nest, called repletes or honey ants. The fluid, digested only to a limited extent while held in the replete's crop, accumulates during times of plenty, resulting in these individuals becoming so distended that they have difficulty moving and are forced to remain permanently in the nest, generally suspending themselves from the ceiling. They can retain these fluids for extended periods and during times of shortage, freely distribute their fluids to the remainder of the colony through trophallaxis. Thus the crops of all the workers taken together serve as a social stomach from which the colony as a whole draws nourishment throughout the year.

Photo Gallery

Repletes are used as living storage vessels, accumulating food when available and dispensing it when needed.
Leptomyrmex erythrocephalus replete worker in an artificial nest. Repletes store liquid foods and water within their gasters. This adaptation helps the ants better survive in times of drought, when food and water are scarce. Photo by Jordan Dean.
Replete worker in Leptomyrmex darlingtoni. Photo by Alex Wild.
Replete soldier in Carebara perpusilla. The much enlarged gaster of soldiers makes them more effective repletes than the workers. Photo by Adam Khalife.
Replete soldier and worker in Carebara jajoby. Photo by Christian Peeters.
Replete and non-replete soldiers in Carebara jajoby. Photo by Christian Peeters.
Replete of Proformica ferreri next to normal worker. From Sierra Nevada, Spain. Photo by Patrick Landmann.
Replete workers in Myrmecocystus. Photo by Greg Hume.

Who Can Become a Replete

In monomorphic species, any worker can become a replete. However, in polymorphic species, the gaster in soldiers is larger than in minor workers and this allows soldiers to be efficient repletes (e.g. Carebara jajoby, Colobopsis nipponica, Pheidole desertorum).

Large Gaster but not a Replete

True repletes are generally obvious and easily identified. However, extended gasters can be caused by factors others than food accumulation.

The enlarged gaster of this Camponotus consobrinus worker is the result of collecting honeydew while foraging on trees.

Foraging workers will often return to their nests with enlarged gasters, but will return to normal size shortly after entering her nest.

Ortiz-Sepulveda et al. (2019) - In the original description of Brachymyrmex giardi, Emery (1895: 215) described a worker, a replete, and a queen, and the replete is what we consider here as a putative worker-queen intercaste, because a regular queen was also reported by Emery (1895). Note that this queen was indicated to be wingless; however, after studying the material, we confirm that it represents a real queen rather than an ergatoid, and the replete has, as mentioned above, a hybrid morphology between queen and worker. Upon dissection of the abdomen of the replete, Emery (1895: 215) reported that the crop is full of honey-like liquid, but also that the ovaries are more developed than in normal workers, and that these repletes likely have a reproductive function. Nevertheless, he considered nourishment their primary function, as is confirmed by De Zolessi et al. (1978). In summary, the exact affinity of these repletes is uncertain: if it were ergatoid queens we would not expect a regular queen to be present (Peeters 1991), which points to an intercaste, because intercastes co-exist with a regular queen. However, intercastes do not usually participate in reproduction (Peeters 1991). Given all the available data, we consider these specimens for now to be a putative worker-queen intercaste, as mentioned before, but the intriguing issue of the repletes in B. giardi requires further study.

The nematode Pheromermis villosa in a Camponotus from Holland (Poinar, 2012, Fig. 8).

Nematode infested workers often have extended gasters.

One characteristic of Prenolepis imparis colonies is the presence of workers with greatly extended gasters. Corpulents were once believed to be true repletes like those of genus Myrmecocystus (Wheeler 1930a; Talbot 1943) until Tschinkel (1987) determined that their enlarged state is actually caused by hypertrophied fat bodies and not the result of crop distention from retained liquid food. Prenolepis imparis is a generalist omnivore (Wheeler 1930a).

Species With Repletes

In general, species with repletes are scattered among the ants, with little apparent phylogenetic signal. The exceptions to this pattern are found in the genera Leptomyrmex and Myrmecocystus, where most or all species have repletes, and in Pheidole, although here the relationships among species has yet to be determined.

The following species are known to have replete workers.

Refeences