Ropalidia fasciata

Appearance

"R. fasciata" appears with a red-brown body with yellow stripes, and some black and yellow markings. The species are variable in color pattern, displaying the black markings to various degrees. Queen-like and worker-like individuals are not morphologically distinguishable, but instead are differentiated based on behavior.

Naming

"R. fasciata" nests are often predated upon by various species of ants, which attack immature "R. fasciata" individuals and can have a severe impact on nest survival. An ichneumonid parasite "Arthula formosana" commonly parasitizes R. fasciata nests. The frequency of parasitism has been shown to increase during the summer months.

Distribution

"R. fasciata" is distributed consistently throughout grasslands within its range, mainly inhabiting fields that are invaded by the sugarcane "Miscanthus sinensis". The wasps prefer to build nests under the leaves of this plant.

Behavior

All species within the subfamily Polistinae, including "R. fasciata", are understood to be eusocial. The insects fall into two categories: monogynous, with a single female reproductive, and polygynous, with several. In "R. fasciata", monogyny is said to be facultative. Subordinate females' reproductive capacity is only partially inhibited biologically or behaviorally suppressed. First brood females emerge and mate before overwintering. Males emerge in late May and attempt matings with workers and foundresses. It is unknown if the foundresses monopolize reproduction, and this is an important question as it defines the function of the caste system of this species. Nests are reconstructed and eggs are laid in March.

Reproduction

Reproductive suppression does not appear to be a major part of "R. fasciata"’s strategy. 'First brood' females have the option to found their own colony, lay eggs, or work for their natal colony. Multiple egg laying females contribute to a colony, and interactions between these females appear to be mild.
It has been suggested that through a subtle dominance hierarchy among foundresses, the queen-like individual can suppress the oviposition of others, but observers have recorded little aggression of dominant or suppressive behavior to support this.All species within the subfamily Polistinae, including "R. fasciata", are understood to be eusocial. The insects fall into two categories: monogynous, with a single female reproductive, and polygynous, with several. In "R. fasciata", monogyny is said to be facultative. Subordinate females' reproductive capacity is only partially inhibited biologically or behaviorally suppressed. First brood females emerge and mate before overwintering. Males emerge in late May and attempt matings with workers and foundresses. It is unknown if the foundresses monopolize reproduction, and this is an important question as it defines the function of the caste system of this species. Nests are reconstructed and eggs are laid in March.

Food

Individuals in a colony habitually share food with one another. One wasp will transfer nectar or water by mouth to another wasp by regurgitation. This behavior takes place between individuals who have not received any food recently, and the touching of mouthparts will occur even when there is no food to be transferred. Liquid food sharing between individuals typically reinforces the dominance hierarchy in similar species of wasp, but in "R. fasciata" this behavior appears to be a simple nutrition sharing technique or even a greeting, unrelated to dominance.

Defense

"Ropalidia fasciata" and related species construct nests by collecting fibers from dead vegetation, mixing them with saliva, and using this mixture to construct vertical cells. The resulting material has a paper-like structure, hence their common name, the paper wasp. "R. fasciata" often builds additional satellite nests as alternatives to the nest where the colony resides. That way if the main nest is destroyed, damaged, or threatened, at least some of the group can move to another nest. Occasionally, groups may relocate to a new nest without obvious cause. The immature wasps in the colony are moved to the new location by adults. Both foundresses and their progeny will help reconstruct a nest. "R. fasciata" foundresses do not disperse far from their natal nests, and foundresses of the same nest are often sisters. In this species, it has been shown that if many females collaborate to found a nest, it will grow faster and have a higher survival rate than one with fewer foundresses.