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Ponerine Ant

Hypoponera opacior


Smith (1936) - P. opacior is highly variable in color, sculpture and the shape of the petiole. From other species the worker can be distinguished by its slender, graceful appearance, finely punctate body, and distinctly triangular shaped petiole (viewed in lateral profile). This species may be part of a species complex, which is consistent with its variable morphology. Workers and queens have a high petiole that is strongly narrowed above in lateral view. Small, reddish brown individuals can be confused with Hypoponera punctatissima, but the latter species has a smooth, shining mesopleuron, and a less elevated petiole than H. opacior. This last character state is very useful for sorting specimens, but is not easily quantified and requires a little practice in its use. Workers of H. opacior also have conspicuous punctures on the central portion of the mandible, while this area in H. punctatissima is smooth and shining. Male H. opacior have light brown wing veins (unlike H. opaciceps), and are most similar to males of Hypoponera inexorata. The latter species is considerably larger (3mm or more in length). We have occasionally found ergatoid queens (or workers with large eyes).


Soil, leaf litter, and under plant pots in my backyard. This one was seen under bamboo leaf litter in my vegetable garden. Ponerine ants nest in rotten wood, in grass sod, under rocks, and in leaf litter. I once even found a colony in my worm bin!


"Most ant males are wasp-like and winged, adapted for dispersing away from their home nest to mate with queens from other colonies. But some Hypoponera males are inbreeding specialists. These pale creatures are worker-like in appearance and mate with their sisters in the nest. Fiotzik and colleagues have studied aspects of the reproductive biology of this species. From the abstract of Fiotzik et al. (2002): Wingless (apterous) males of Hypoponera opacior sat on top of queen cocoons, inserted their genitalia into the cocoons and remained in copula with cocooned queens for up to 40 h. These males were tolerant of each other; fighting was never recorded. Our observations therefore suggest that wingless males of H. opacior ensure reproduction by copulatory mate guarding. This strategy, although time consuming, presumably reduces the likelihood of subsequent inseminations by other males. Apterous H. opacior males have only a limited amount of sperm available: histological preparations showed that, in contrast to Cardiocondyla fighter males, the testes degenerate in early adult life. Males of H. opacior have relatively few mating opportunities. Although some wingless males were reproductively active for more than 3 weeks, we observed a maximum of only six matings per male, with a mean slightly above one. Some H. opacior males used an alternative reproductive tactic of dispersal and outbreeding. We found colonies headed by single, dealate queens, which did not rear wingless sexuals but presumably reproduced through winged reproductives that mate in nuptial flights. The social structure of those colonies contrasted with nests containing wingless reproductives, which were highly polygynous and polydomous. From the abstract of Fiotzik et al. (2010): The ant Hypoponera opacior exhibits alternative reproductive morphs of males and females associated with distinct sexual behaviours. Our long-term study reports strong seasonality in sexual production with a mating season in early and one in late summer. Winged (alate) reproductives emerge in June, swarm during the monsoon season and establish new colonies independently. In contrast, wingless worker-like (ergatoid) reproductives that appear in late August mate within their natal or adjacent nests and either do not disperse or establish new nests close by. These divergent dispersal patterns allowed us to analyse the impact of local factors on investment strategies by comparing sex allocation between and within the two reproductive events. The optimal sex ratio for ergatoid reproductives should be influenced both by competition for matings between brothers (local mate competition) and rivalry among young locally dispersing queens for workers, nest sites or food (local resource competition). The greater importance of local resource competition was demonstrated both by a male-biased sex ratio for wingless sexuals and a stronger increase in the number of males with total sexual production than for the number of queens. Microsatellite analysis revealed that inter-nest variation in relatedness asymmetry cannot explain split sex ratios in the August generation. Instead, nests with related ergatoid males raised a male-biased sex ratio contrary to the expectations under local mate competition. In conclusion, male bias in wingless H. opacior indicates that local mate competition is less strong than local resource competition among ergatoid queens over the help of workers during nest foundation. From the abstract of Fiotzik et al. (2011): The ant Hypoponera opacior exhibits alternative reproductive morphs associated with distinct sexual behaviours. Wingless, worker-like gynes mate in fall in their mother nest. Subsequently, these polygynous nests divide and wingless queens disperse on foot accompanied by workers, which help during nest foundation. Local resource competition amongst wingless queens was indicated by male-biased sex ratios. Queens compete over access to workers, and this competition manifests in dominance interactions. We colour-marked queens and workers to study this behaviour. Marked queens were treated aggressively and frequently killed by nestmates, whilst similarly labelled workers were readopted. We hypothesise that mated wingless queens—although they resemble workers in external morphology—differ chemically and that fertile queens with divergent odours are not tolerated. Thereby, sterile H. opacior workers avoid the risk to raise offsprings of unrelated queens. However, when nests split, workers should base their decision which queen to follow not only on relatedness, but also on queen fertility. Cuticular hydrocarbon profiles of queens could serve as an honest signal for workers. Indeed, gas chromatography showed that hydrocarbon composition differs between workers and mated queens and is linked to ovary development in queens. Workers and unmated queens exhibit complex profiles of short-chained hydrocarbons, whilst fertile queens carry few, long-chained alkenes and branched alkanes. Furthermore, ovary length was correlated to the relative amounts of characteristic hydrocarbons of queens. The chemical profile was also associated with eye size—an unalterable trait in adult insects—suggesting that larval nutrition and consequently body size affects adult ovary development. Kureck et al. (2011) investigated whether wingless sexuals of the ant Hypoponera opacior adjust mate-guarding behaviour to the level of competition in the nest. Males mate with young nestmate females shortly before these emerge from the cocoon. Aggressive interactions among adult males have never been observed, but males embrace and guard the cocoons of their mating partners for up to 2 days. In laboratory experiments, the duration of pupal guarding increased with the number of adult males in the nest, but decreased with an increasing number of mating partners per male. These findings demonstrate that males are aware of the competitive situation in the nest and adjust their mating behaviour in an adaptive manner. Males also guarded and attempted to copulate with sterile worker and male pupae. These misdirected behaviours might be the result of identification errors, as we found that the cuticular hydrocarbon profiles of young individuals of the different castes were very similar. Copulatory behaviour towards sterile workers is certainly maladaptive, whereas interactions with young males may provide a fitness benefit: We found a high mortality rate of young males that were embraced and guarded by adult males. Adult maleemale pupae interactions predominantly occurred when only a single male was present in the nest. In addition, single-male nests were found at unusually high frequencies. These findings suggest that wingless males try to kill their pupal rivals through embracing when there are few adult competitors in the nest, but switch to mate-guarding behaviour when intramale competition is high."

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Spotted by

Eugene, Oregon, United States

Spotted on Aug 2, 2021
Submitted on Aug 3, 2021

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