Entomological Science最新文献

The evolution of exaggerated sexual traits may be possible by the relaxation of various constraints on exaggeration. Functional constraints refer to the reduced performance of exaggerated traits per se or increased survival costs by holding the exaggerated traits. Genetic constraints, such as genetic correlations or pleiotropy, may hinder the independent evolution and exaggeration of traits. Structural constraints, such as competition for space and resources among traits, may require the coordination of the exaggerated trait with surrounding structures. The remarkable diversity of male genital morphology provides an ideal opportunity for examining constraints on sexual trait exaggeration. In this study, we addressed the constraints on the evolution of exaggerated male genital morphology based on a comparative analysis of phenotypic covariation between the genitalia and other body parts using Ohomopterus ground beetles. We found that exaggerated male genitalia were related to a relaxation of functional constraint, as revealed by a steeper allometric slope in the species with exaggerated male genitalia. By contrast, genetic constraint based on a shared genetic basis for the male genitalia and other appendages may have little effect on diversification in male genitalia. Structural constraints were strongest in the species with the most exaggerated male genitalia, suggesting that the observed constraint was a result of exaggeration. These findings improve our understanding of sexual trait exaggeration and underlying constraints.

Variation in body color occurs in many animals, and its function differs by species. Some species use multiple colors to create different effects. Most dragonflies change their body color unilaterally with maturation, whereas in a few species these changes are reversible. Both sexes of the damselfly Indolestes peregrinus show temperature-dependent reversible body color changes, with a brown color when the ambient temperature decreases and a blue color when the temperature increases. To elucidate the temperature range at which this color change occurs and the exact elapsed time for the color change, laboratory experiments were conducted to determine whether the time required for body color change was related to ambient temperature and whether sex differences affected this duration. The body color and time required for the change were recorded under four temperature conditions. Bluing was completed in a few minutes, whereas browning took several hours. Moreover, sexual differences were observed, whereby males showed a more rapid transformation to blue than that of females. Our results suggest that the rapid bluing has some importance in this species, especially in males.

In the beetle family Carabidae, feeding habits are important life history traits that determine their role in ecosystems and suitability as bioindicators. However, they have not been elucidated for most species, especially in the larval stages. Using laboratory-rearing experiments, this study examined the larval feeding habits of two large carabid species: Lesticus magnus (tribe Pterostichini) and Chlaenius costiger (tribe Chlaeniini). Although previous studies failed to rear these larvae on insect larva diets, the mandible morphology of the first instars described in those studies, together with subsequently obtained knowledge of the relationship between mandible morphology and feeding habits in other carabid larvae, suggests that they are earthworm feeders. Rearing experiments with three types of animal diet (insect larvae, mixed snail and slug, and earthworm diets) showed that as expected, their larvae are earthworm feeders. In L. magnus, although the larvae accepted the mixed snail and slug diet and the earthworm diet, only larvae reared on the earthworm diet reached adulthood. In C. costiger, the larvae accepted only the earthworm diet and reached adulthood. This is the first report of earthworm feeding during the larval stage for the genus Lesticus (tribe Pterostichini) and tribe Chlaeniini. The importance of these results is discussed from ecological and evolutionary perspectives.

The genus Neotrogaspidia Lelej, 1996 is a small group of velvet ants with five species from the Australasian, Oriental and Palearctic Regions. The type species, N. pustulata (Smith, 1873) (♂♀), is the only Northeast Asian species known at present. In this paper, N. elpinice (Mickel, 1933), stat. resurr. et comb. nov. (♂♀) is resurrected from the junior synonym of N. pustulata. Two new combinations are proposed for N. circumcincta (André, 1896), comb. nov. (♂♀) from Orientidia Lelej, 1996 and N. recticarinata (Chen, 1957), comb. nov. (♂) from Trogaspidia Ashmead, 1899. New synonymies are proposed for N. elpinice with T. aestivalis Hammer, 1949, syn. nov. and T. maritima Chen, 1957, syn. nov., and N. circumcincta with T. yuliensis Tsuneki, 1972, syn. nov. and Krombeinidia agricola Williams, 2019, syn. nov. An updated genus diagnosis and a key to all described species are provided. New records include N. circumcincta from Laos and Vietnam, N. pustulata from North Korea, and N. recticarinata from Taiwan. The inflated endophallus of the male genitalia of N. pustulata is illustrated. A potential host record, habitat records and mating observations of Neotrogaspidia are presented. The historical process of formation of the distributional patterns of this genus in Northeast Asia is discussed.

Altitudinal distribution and seasonal life cycle of drosophilid flies (Diptera) were studied on the southwestern slope of Mt. Higashi-Kagonoto in Tomi and at Ishi-no-yu in Shiga Heights, Nagano, central Japan. Collections of flies were carried out from early spring to late autumn using traps baited with fermenting banana. Based on the present results and previous faunal reports from central Japan, major native drosophilid species collected in this study were classified into migratory (5 species), high-altitude (6), mid-altitude (14) and low-altitude (14) species. The migratory species are assumed to perform extensive seasonal migration between low- and high-altitude areas. Among these native species, Drosophila alpina (a high-altitude species) and D. moriwakii (a mid-altitude species) are assumed to pass only one generation in a year, while the others pass two or more generations. Five of the six high-altitude species are assigned as the Palearctic elements, while four of the five migratory species and 12 of the 14 low-altitude species are assigned as the Sino-Japanese elements. The mid-altitude species consist of approximately equal numbers of the Palearctic and Sino-Japanese elements. Among the high-altitude species, D. alpina and Hirtodrosophila makinoi are also distributed in high-altitude areas in Hokkaido, northern Japan. The other high-altitude species and most of the mid-altitude species generally occur in low-altitude areas in Hokkaido or the further north. The Sino-Japanese elements occurring at high and mid altitudes in central Japan are also distributed at high altitudes in southern and southwestern China.

Ants are widespread in all terrestrial habitats, and competitive interactions between species are common. Although redistribution of food within a colony may buffer the negative effects of temporary resource shortages, colony functionality can be compromised when famine is prolonged. One of the possible effects of famine is impairment of the fighting ability of species, with cascade effects on community. Here, we investigated whether food shortage alters the fighting ability of workers of three dominant species in the Mediterranean area: the invasive alien species, Lasius neglectus and Linepithema humile, and one highly polydomous autochthonous species belonging to the Tapinoma nigerrimum complex. We performed laboratory tests of interspecific one-on-one aggression and pairwise group contests between species, with all possible combinations of artificially satiated and starved groups. Results showed that starvation had a scarce effect on the individual aggressiveness in all three species. Similarly, the outcomes of the group fights were only lightly affected, but with an important exception. The positions of species in the fighting hierarchies were in most cases clear and linear, with L. neglectus at the top. However, we found that L. humile and L. neglectus showed equal mortality when one of the two species was starved and the other satiated. Although we investigated only one aspect of competition, that is, fighting ability, our results provide a piece of the complex jigsaw of competitive interactions of ants, and suggest that food deprivation can be a determinant that alters the relationships between ants and promotes or hampers the coexistence of dominant species.

Rove beetles (Staphylinidae) are one of the largest families in Coleoptera. Although the ecological features of rove beetles are important subjects in terms of understanding their diversification processes, laboratory-rearing studies have only been conducted for a few species to date. In this study, we established a continuous rearing method for Anotylus amicus (Bernhauer, 1923) (Staphylinidae: Oxytelinae) using bell cricket food. In addition, its life cycle, behavior and morphological variations were investigated using the rearing technique. The mean duration of egg, first, second and third instars, prepupa and pupa were 4.3, 4.0, 4.0, 7.8, 1.7 and 4.7 days at 24°C, respectively. Adults and larvae used substrate, food and excrement for nesting. Mate guarding by males and associated male–male combat were observed. Head width and body size sexually varied; most males were larger than females, but some were comparable to females. Many individuals possessed undeveloped short hindwings, while some, especially large females, had long ones. As A. amicus can be reared simply, have a fairly short generation period, and exhibit interesting behavioral and morphological characteristics, A. amicus is suitable for clarifying the ecological aspects of rove beetles.

The importance of visual stimuli in a given behavior is often different, even between closely related species. Species of the genus Drosophila have been categorized into three classes according to their reproductive dependency on vision. Class I and II species reproduce in the darkness, whereas class III species never reproduce without vision. Therefore, in class III species, mutants at the white locus that are deprived of normal visual function are not able to be established as homozygous stocks. Drosophila prolongata is a species with a conspicuous body color pattern, suggesting that an increased importance of visual stimuli underlies the evolution of this species. In this study, to examine the behavioral dependency on visual stimuli in D. prolongata, we generated white gene-knockout (w⁻) mutants using the CRISPR/Cas9 system and examined their mating and fighting behaviors in light and dark conditions. The courtship and fighting activities of w⁻ males were extremely reduced regardless of the light condition. Furthermore, wildtype males did not perform any courtship or fighting behaviors in dark conditions. Our results showed that D. prolongata is a class III species that strongly relies on visual stimuli in both behaviors.