Some ants have morphologically distinct subcastes among workers, divided into minor workers, which are smaller, and major workers, which are larger and often have enlarged heads. Minor workers perform general tasks, while major workers often have more specialized roles, such as nest defense and nutritional storage. In addition to morphological caste differences, age plays an important role in polyethism. Generally, young workers having high fat mass become nurses, while old workers with reduced fat mass shift to foragers. However, few studies have examined the relationship between subcaste and age-dependent division of labor, and associated physiological changes. In this study, we used Camponotus yamaokai, which exhibits clear dimorphism among workers, to clarify the specialized roles of major workers in terms of behavior and physiology. We found that major workers rarely forage or leave the nest but instead defend the nest by plugging the nest entrance when heterospecific competitors are present in the feeding area. In histological observation of the lipid storage organ (i.e. fat body), minor workers showed a reduction in fat body size with aging, the typical of worker age-dependent changes. On the other hand, physiological changes with aging were minimal in major workers. These findings indicate that major workers of C. yamaokai maintain a stable, `young' physiological state and are specialized for intranidal nest defense, rarely shifting to extranidal tasks with age.
Republic of Korea (South Korea) lies between the Eurasian continent and the Japanese archipelago and spans temperate to subtropical climates. The geographic position of South Korea provides a biogeographic bridge that promotes high ant diversity. Recent taxonomic revisions are, however, generally lacking, and North Korean records are often merged uncritically with those of South Korea, underscoring the need for a comprehensive update. In this study, we provide an updated checklist of the ants of South Korea based on extensive field collections, critical examination of museum specimens, and a comprehensive review of published records. We recognize 147 valid species belonging to 44 genera in South Korea, with 22 species reported here for the first time. The updated list also recognizes six endemic species and thirteen non-native species, five of which are newly confirmed in South Korea (Monomorium carbonarium (Smi@ 1858), Nylanderia sp. cf. jaegerskioeldi (Mayr, 1904), Pheidole parva Mayr, 1865, Technomyrmex vitiensis Mann, 1921, and Tetramorium lanuginosum Mayr, 1870). Based on the literature and museum investigations, we also remove 31 species previously reported from South Korea. In addition, we present morphological descriptions and ecological information for the newly reported species and Camponotus dorex Fisher, 2025, a South Korean endemic with previously limited information. The checklist also identifies five dubious species and provides revised taxonomic treatments of problematic taxa, notably designatingAphaenogaster schmidti Karavaiev, 1912 as a nomen dubium. We further discuss distribution patterns, highlight ecological features such as endemism and potential future discoveries, and assess the current status and risks of introduced ants. This work offers the most comprehensive and up-to-date framework for understanding the diversity, distribution, and conservation priorities of South Korean ants.
Leptamlline ants are cryptic, and our comprehension of their natural history remains incomplete. We collected one colony of Leptanilla kubotai in October 2023 and investigated the colony composition and behavioral characteristics of this rare species. The nest of Leptanilla kubotai was situated 15 cm deep in the soil and contained one dichthadiiform queen, 453 workers, and 663 larvae. The queen had 88 ovarioles, while the workers had no ovaries. Workers were specialized predators of geophilomorph centipedes, and promptly recruited nestmates upon encounter with a prey. Larvae showed remarkable mobility, associated with unique morphological features: a ventral hooked claw on their prothorax and a row of teeth on the external margin of their mandibles. The queen and workers performed larval hemolymph feeding and likely rely on larvae for nutrition in the absence of prey. We compare these findings to other Leptanillinae and discuss the specialization of Leptanilla for a subterranean lifestyle.
Protective mutualism between ants and Macaranga genus plants ranges from obligate to facultative interactions. Unlike obligate ant-plant interactions, facultative mutualists like Macaranga tanarius lack specialized structures to house ant symbiont colonies but offer food rewards such as extrafloral nectary secretions and food bodies. These rewards attract opportunistic foraging ants that provide defense against insect herbivores. We hypothesized that the efficacy of this defense depended on the composition of the ant species. We assessed insect herbivory by recording leaf damage and monitored ant activity at different times of the day. We also conducted behavioral assays to test ants' response toward offered wax-moth larvae prey (representing lepidoptera larva that causes most leaf-loss damage of M. tanarius). Ant community composition did not differ between day and dusk, with almost half of the species (48.4%) active at both times. Saplings with foraging ants showed a trend of higher leaf loss (mean = 2.13%) than saplings without ants (mean = 1.32%), contrary to our expectations, although this difference was not statistically significant. This could be due to the short observation time in this study, as herbivore attacks on leaf loss may be accumulated over a longer period. Most ant visitors on M. tanarius, which relied on herbivory diets, ignored the prey items; only the yellow crazy ant Anoplolepis gracillipes consistently attacked offered prey. Future research should be carried out over a longer period, and the abundance of ant species patrolling M. tanarius should be recorded to understand the potential roles of ants on these plants.
Hainan Province is a tropical island identified as a global biodiversity hotspot, but limited sampling and taxonomic efforts have been conducted to catalog and describe its ant fauna. Here, we compiled valid historical records and new records based on past and recent ant surveys, to present the first checklist of ants specific to Hainan. In total, we identified 10 subfamilies, 67 genera, and 237 species, a 60% increase in the previous species checklist. A total 25 genera and 89 nominal species are newly recorded for the island, and 109 morphospecies are detected. The checklist also includes 15 exotic species, among which Pheidole megacephala (Fabricius, 1793) and Solenopsis invicta Buren, 1972 can be considered as invasive. Despite this update, we provide several lines of evidence to argue that the Hainan ant fauna remains largely understudied. Together, these findings not only highlight the rich biodiversity present but also the importance of increasing the species cataloguing rate and taxonomic work for the island. The use of additional sampling approaches, and new surveys targeting a wider geographic and ecological span might represent an efficient approach to fill this knowledge gap.
