Winter Activity of Ants in an Urban Area of Western Japan

During winter, foraging activity of ants is considered low in temperate regions. Winter activity of ground-dwelling ants was investigated using bait traps and quadrat sampling in an urban area of Fukuoka City, western Japan. Six study sites were grouped into two categories: 4 open land types and 2 forest types. A total of 18 ant species were recorded between the end of January and beginning of March. The foraging activity of ants was generally low, except during relatively warm periods when the surface ground temperature was above 6℃–7℃ or soil temperature was above 4℃–5℃. Tetramorium tsushimae, Messor aciculatus, and Pheidole noda were the most abundant in the open land type, whereas Nylanderia flavipes, P. noda, and Crematogaster osakensis were the most abundant in the forest type. Bait preference varied among the different species, e.g., P. noda preferred tuna over honey, whereas N. flavipes similarly responded to tuna and honey. This is the first detailed study on the relationship between temperature and ant activity in Japanese mainland fauna.

Social transmission of information about a mutualist via trophallaxis in ant colonies

Partner discrimination is crucial in mutualistic interactions between organisms to counteract cheating by the partner. Trophobiosis between ants and aphids is a model system of such mutualistic interaction. To establish and maintain the mutualistic association, ants need to correctly discriminate mutualistic aphids. However, the mechanism by which ants recognize aphids as their partners is poorly understood, despite its ecological and evolutionary importance. Here, we show for the first time the evidence that interaction with nest-mates that have tended aphids ( Aphis craccivora ) allows ants ( Tetramorium tsushimae ) to learn to recognize the aphid species as their partner. When ants had previously tended aphids, they moderated their aggressiveness towards aphids. More importantly, ants that had interacted with aphid-experienced nest-mates also reduced their aggressiveness towards aphids, even though they had never directly experienced them, indicating that aphid information was transmitted from aphid-experienced ants to inexperienced ants. Furthermore, inhibition of mouth-to-mouth contact (trophallaxis) from aphid-experienced ants to inexperienced ants by providing the inexperienced ants with artificial honeydew solution caused the inexperienced ants to become aggressive towards aphids. These results, with further supporting data, strongly suggest that ants transfer information on their mutualists during trophallactic interactions.

Nonintegrated Host Association ofMyrmecophilus tetramorii, a Specialist Myrmecophilous Ant Cricket (Orthoptera: Myrmecophilidae)

Myrmecophilusant crickets (Orthoptera: Myrmecophilidae) are typical ant guests. In Japan, about 10 species are recognized on the basis of morphological and molecular phylogenetic frameworks. Some of these species have restricted host ranges and behave intimately toward their host ant species (i.e., they are host specialist). We focused on one species,M. tetramorii, which uses the myrmicine antTetramorium tsushimaeas its main host. All but oneM. tetramoriiindividuals were collected specifically from nests ofT. tsushimaein the field. However, behavioral observation showed that all individuals used in the experiment received hostile reactions from the host ants. There were no signs of intimate behaviors such as grooming of hosts or receipt of mouth-to-mouth feeding from hosts, which are seen in some host-specialistMyrmecophilusspecies among obligate host-ant species. Therefore, it may be thatM. tetramoriiis the species that is specialized to exploit the host by means other than chemical integration.