Mamoru Terayama

Intraspecific Variation of Cuticular Hydrocarbon Composition in Formica japonica Motschoulsky (Hymenoptera: Formicidae)

Abstract Cuticular hydrocarbons and morphological features were compared among 80 Formica japonica colonies collected in Japan. Although a few morphological differences were found in workers among the colonies, four different types of cuticular hydrocarbon composition were observed. This was supported by a principal component analysis. We further compared the cuticular hydrocarbons among a total of approximately 400 F. japonica colonies, and categorized the hydrocarbon components into four types based on the result of discriminant analyses for the first 80 colonies. Type 1 was observed in colonies mainly collected in southern Honshu, Shikoku, and Kyushu. Types 2, 3, and 4 were from colonies with primary collections in Southern Honshu, central and Pacific coast northern Honshu, and the Sea of Japan coasts of northern Honshu and Hokkaido, respectively. The occurrence of four distinct types of CHC composition suggests that the colonies that produce them are separate species.

Intercontinental union of Argentine ants: behavioral relationships among introduced populations in Europe, North America, and Asia.

Many invasive ants, including the Argentine ant Linepithema humile, form expansive supercolonies, within which intraspecific aggression is absent. The behavioral relationships among introduced Argentine ant populations at within-country or within-continent scales have been studied previously, but the behavioral relationships among intercontinental populations have not been examined. The present study investigated the levels of aggression among intercontinental Argentine ant populations by transporting live ants from Europe and California to Japan and conducting aggression tests against Japanese populations. Workers from the dominant supercolonies of Europe and California did not show aggressive behavior toward workers from the dominant supercolony of Japan, whereas they fought vigorously against workers from minor supercolonies. The three massive supercolonies, together with Argentine ants from Macaronesia, may be the largest non-aggressive unit formed by a social insect species in which intraspecific aggression exists. Absence or low levels of aggression at transcontinental scale, which may have derived from low genetic variation, may help introduced Argentine ants maintain expansive supercolonies. The lack of aggression implies possible frequent exchanges of individuals among the intercontinental populations mediated by human activities.

Four mutually incompatible Argentine ant supercolonies in Japan: inferring invasion history of introduced Argentine ants from their social structure

In recent years, highly invasive ant species successively invaded warm regions of Asia. In Japan, the Argentine ant, Linepithema humile, has become established in several coastal regions. This species forms unusual social organizations called supercolonies consisting of numerous mutually non-aggressive nests. We studied the behavioral relationships, similarity of cuticular hydrocarbon profiles (nestmate recognition cue), and genetic relationships among the introduced Argentine ant populations of Japan. The Japanese populations were divided into four behaviorally, chemically, and genetically distinct supercolonies, which may have derived from independent source populations. The result represents the recent trend of increasing invasions of invasive ants to Asia. The discontinuous distribution of one supercolony throughout most of the Japanese range suggests rapid expansion of the supercolony via human-mediated jump dispersal. Meanwhile, localization of the other three supercolonies in Kobe Port provides the first evidence for multiple invasions of distinct supercolonies into a base for international trade.

Distribution of the Argentine ant, Linepithema humile, along the Seto Inland Sea, western Japan: result of surveys in 2003-2005.

The distribution of the Argentine ant, Linepithema humile, was investigated in 65 cities or towns along the Seto Inland Sea, western Japan in 2003–2005. Our results include all available information of their distribution in Japan until 2005. Argentine ants have invaded Aichi Prefecture (Tahara‐shi), Hyogo Prefecture (Kobe‐shi), Hiroshima Prefecture (Hiroshima‐shi, Fuchu‐cho, Hatsukaichi‐shi, Ono‐cho and Otake‐shi), and Yamaguchi Prefecture (Iwakuni‐shi and Yanai‐shi). The most widespread distribution was found around Hatsukaichi‐shi including the westernmost part of Hiroshima‐shi and the easternmost of Ono‐cho.

Combined use of a synthetic trail pheromone and insecticidal bait provides effective control of an invasive ant

BACKGROUND Except for sex pheromones, use of pheromones in pest management has been largely unexplored. A high concentration of trail pheromone disrupts ant trail following and foraging, and thus synthetic trail pheromone can be a novel control agent for pest ants. In this study, a year-long treatment of small areas (100 m(2) plots of urban house gardens) with synthetic trail pheromone, insecticidal bait or both was conducted to develop a novel control method of the invasive Argentine ant Linepithema humile (Mayr). RESULTS The ant population could be maintained lower than or similar to the initial level only by combined treatment with synthetic trail pheromone and insecticidal bait. Actually, the ant population was nearly always lowest in combination treatment plots. Throughout the study period, the ant population in plots treated with either one of synthetic trail pheromone or insecticidal bait remained similar to no-treatment plots. CONCLUSIONS Combination treatment may be a more effective and environmentally friendly method for controlling invasive ants than conventional methods. Extermination of ants by insecticidal bait and inhibition of re-infestation by pheromone may be the mechanism of the combination effect. This is the first study to show a significant effect of synthetic trail pheromone on ant population.

Workers select mates for queens: a possible mechanism of gene flow restriction between supercolonies of the invasive Argentine ant

Some invasive ants form large networks of mutually non-aggressive nests, i.e., supercolonies. The Argentine ant Linepithema humile forms much larger supercolonies in introduced ranges than in its native range. In both cases, it has been shown that little gene flow occurs between supercolonies of this species, though the mechanism of gene flow restriction is unknown. In this species, queens do not undertake nuptial flight, and males have to travel to foreign nests and cope with workers before gaining access to alien queens. In this study, we hypothesized that male Argentine ants receive interference from workers of alien supercolonies. To test this hypothesis, we conducted behavioral and chemical experiments using ants from two supercolonies in Japan. Workers attacked males from alien supercolonies but not those from their own supercolonies. The level of aggression against alien males was similar to that against alien workers. The frequency of severe aggression against alien males increased as the number of recipient workers increased. Cuticular hydrocarbon profiles, which serve as cues for nestmate recognition, of workers and males from the same supercolony were very similar. Workers are likely to distinguish alien males from males of their own supercolony using the profiles. It is predicted that males are subject to considerable aggression from workers when they intrude into the nests of alien supercolonies. This may be a mechanism underlying the restricted gene flow between supercolonies of Argentine ants. The Argentine ant may possess a distinctive reproductive system, where workers participate in selecting mates for their queens. We argue that the aggression of workers against alien males is a novel form of reproductive interference.

The ant genus Leptanilla: discovery of the worker-associated male of L.japonica, and a description of a new species from Taiwan (Hymenoptera: Formicidae: Leptanillinae)

The male and female of Leptanilla japonica Baroni Urbani are described. This is the first worker‐associated male to be discovered in subfamily Leptanillinae. Leptanilla taiwanensis is described as new based on the worker and female from Taiwan, the first record of Leptanillinae from the island. An ecological note on the food of the ants is given. Implications of the male morphology and taxonomic positions of the other leptanilline genera based on males are discussed.

The subsocial wood-feeding cockroach genus Salganea Stål from Borneo, with description of a new species (Blaberidae: Panesthiinae)

Abstract The Bornean species of the subsocial wood-feeding cockroach genus Salganea Stal is reviewed. We found nine species, of which S. nalepae Maekawa & Matsumoto is described as new and S. guentheri Roth is recorded for the first time. The previously unknown female of S. perssoni Roth and male of S. obtusespinosa Princis are described. A key to the species is presented.

Two new species of the genus Carminator Shaw from Japan, the northernmost record of extant Megalyridae (Hymenoptera)

The family Megalyridae is recorded from Japan for the first time on the basis of two new species, Carminator helios and C. japonicus. This is the northernmost record of living Megalyridae, although fossil species are known from regions of the Baltic Sea. Carminator helios can be distinguished from congeners of the Asian and Australian regions by the combination of a long head, deeply excavated frons with convex inner margins, entirely striated postgena, the number of fore tibial spines (more than 16), and a long R1 vein. Carminator japonicus is distinguishable from other species by the combination of an orange‐colored metasoma, a weakly excavated frons, and an elongate vertex. This species was collected from the canopy of Acer pictum. Additional characters that distinguish species of the genus Carminator are discussed.

New species of Neoapenesia (Hymenoptera: Bethylidae) from Japan, with special remarks on female morphology and bionomics

A bethylid wasp is described as Neoapenesia makiharai n. sp. based on adults obtained from dead wood collected from the Ryukyus, Japan. The male is distinguishable from N. leytensis Terayama, the monotypic species of the genus, on the basis of the following characteristics: presence of short 2Rs vein, rounded propodeum, absence of sculpture on propodeum, widened subgenital plate, and apically rounded aedeagus. The female of Neoapenesia is described for the first time. Its morphological characteristics closely resemble those of Apenesia, but sex association was confirmed by the following facts: partial mitochondrial COI gene sequences (582 bp) of males and females were identical, and mating behavior was often observed. The female is easily distinguishable from females of Apenesia on the basis of the following characteristics: distinctly short antenna (not reaching posterior margin of head) and a disproportionately large head (head width about twice the dorsal pronotal width). Although females were active at night, males were active in the daytime and copulation was observed during this period. Since the female is larger than the male, phoretic copulation may not occur. Dead wood was collected and kept in plastic bags, from which a total of 16 species of coleopteran wood‐borers and two predators were obtained together with N. makiharai n. sp. Many individuals of N. makiharai n. sp. were reared from dead wood severely affected by Cerecium longicorne and it was the most common species obtained from our wood samples. Therefore, the cerambycid species is considered a potential host species.