Ropalidia marginata is an Old World species of paper wasp. It is primitively eusocial, not showing the same bias in brood care seen in other social insects with greater asymmetry in relatedness. The species employs a variety of colony founding strategies, sometimes with single founders and sometimes in groups of variable number. The queen does not use physical dominance to control workers; there is evidence of pheromones being used to suppress other female workers from overtaking queenship.
R. marginata are a dark reddish color (slightly lighter than Ropalidia revolutionalis), with yellow spots on some joints and a yellow ring around the lower abdomen. Males differ from females by having a weaker mandible and lacking a stinger. The female workers are not morphologically different from the queen and are more distinguishable by behavior.
The distribution of R. marginata extends as far west as Pakistan and as far east as New Guinea, Queensland, and some eastern Pacific islands. They are the most common social wasp in India. Although R. marginata has been studied extensively in India, there is a lack of literature about the animal in other parts of its range.
Males have been experimentally shown to be capable of deliberately delivering food to larvae when females are absent and food surplus is available. Males feed the larvae with the same proportion of individuals as females. They are, however much less efficient than females at feeding. They spend over 90% of feeding bouts masticating and end up feeding far fewer larvae. The males also preferentially feed the largest larvae, resulting in the death of many smaller and younger larvae. It was only possible to observe this behavior by removing all females from a nest and hand feeding the males, as the males cannot forage on their own and have no opportunity to care for larvae if females occupy this role. While males are typically not responsible for feeding larvae in naturally occurring populations, they are capable of doing so.
These predatory wasps are solitary foragers (that means each forager finds the prey, kills it and brings that back to the nest all alone). Foragers typically forage within about 300 to 700 m from their nests, though if food is scarce, they can travel up to about 1.5 km from their nest. With experience, they acquire a vivid familiarity with their foraging range; they perhaps remember the sites from where they have collected food previously. Such familiarity with the foraging landscape eventually helps them to reduce their search for food.
R. marginata makes gymnodomous nests with up to 500 cells and up to 10 pedicels. The nests are made of paper, which are produced by wasps masticating cellulose and mixing it with saliva.The nests are usually found in closed spaces with small openings in natural and man-made structures.
The haplodiploid genetic system creates asymmetry in relatedness of most Hymenoptera species. R. marginata, however, have increasingly unrelated workers and broods because of "simultaneous production of several different patrilines and matrilines within a colony." Serial polygyny works against the inclusive fitness benefits workers have of caring for broods because of reduced relatedness.
Gadagkar devised a unified model that makes predictions about what proportion of the population of R. marginata "should opt for a selfish solitary nesting strategy and what proportion should opt for an altruistic worker strategy" (853). From this, he was able to predict that 5% should opt for the selfish solitary nesting strategy while 95% should opt for the altruistic worker strategy.
Gadagkar et al. genotyped R. marginata mothers and daughters at a "few non-specific esterase loci" to infer the genotypes of the haploid fathers or estimate the number of fathers needed to produce the daughters observed (850). The researchers ultimately found, "R. marginata queens mate with 1–3 different males and the average relatedness among their daughters thus drops from the theoretically expected 0.75 to about 0.50, thus entirely negating the advantage of haplodiploidy for social evolution, as predicted by Hamilton" (851). Gadagkar "found no evidence for intra-colony kin recognition" (851).
Aggression in the form of chasing and sometimes stinging is needed to defend the nests from predators and non-nestmates. Older females from different nests are chased away, as are predators such as Vespa tropica. Dominance relationships, mediated by aggression, control foraging amidst workers. Aggressive behavior is a crucial part of the transition from worker to queen.
