Entomological Science最新文献

Aggressive behavior is important for acquiring crucial resources in many animals. As such behavior is costly, selection favors contestants that can accurately gather information regarding the likely costs and benefits of conflict to enable appropriate tactical decisions. Mate choice based on relatedness is widespread among animals and has severe consequences. Theoretically, due to the potential costs of inbreeding, contestants may benefit from discriminating between relative and nonrelative mates and adjusting their behavior accordingly. If inbreeding results in fitness costs, related mates might be perceived as less valuable and individuals might be expected to invest less in costly aggression, and vice versa. However, the role of male–female relatedness in aggression has been less addressed. The egg parasitoid wasp Anastatus disparis, which exhibits extreme male–male aggressive behavior for mating opportunities, was used as an experimental model to explore the role of male–female relatedness in aggression. Inconsistent with our prediction, male–female relatedness had no significant effect on male–male fighting frequency or intensity in A. disparis. The ability of males to discriminate relative from nonrelative females is a prerequisite for male–female relatedness to affect males’ aggression. However, A. disparis males did not exhibit any mating preferences for relative or nonrelative females. Besides, inbreeding did not result in depression in terms of longevity, fecundity or sex ratio in A. disparis. Our finding of no effect of male–female relatedness on male–male fights in A. disparis may be caused by a lack of kin discrimination ability or/and a lack of benefits from discriminating relatives from nonrelatives.

The genus Aquarius, of the subfamily Gerrinae, was formerly divided into two species and one subspecies in Japan (A. paludum paludum, A. paludum amamiensis and A. elongatus, respectively). Aquarius haliplous Yasunaga et al. 2018 has recently been described as a new species, which occurs in brackish waters of Nagasaki Prefecture and is found sympatrically with the widely distributed species, A. p. paludum. However, they are considered to be speciated, with no cross-breeding. In this study, molecular phylogenetic and morphological analyses were undertaken using the mitochondrial DNA COI (529 bp) and nuclear DNA histone H3 (314 bp) gene regions to investigate the genetic and morphological differentiation in the genus Aquarius, including A. haliplous, throughout Japan (including the islands). The results show that, unlike A. p. paludum, A. p. amamiensis and A. haliplous, A. elongatus displays substantial genetic differentiation. Considering that, although morphological differences exist in the antennae of A. p. paludum and A. p. amamiensis, A. haliplous has no clear genetic or morphological difference from A. p. paludum, and hence cannot be classified as a distinct species. Therefore, we propose that A. haliplous be synonymized with A. paludum.

The biology of Horniolus fortunatus (Lewis, 1896) has been fragmentarily reported, but what the larvae and adults feed on and the immature stages are still unknown. In this article, I report that this coccinellid adult and larva feed on mealybugs (Planococcus sp.) living in the nest of the ant Crematogaster matsumurai Forel, 1901.

Adults and various immature stages of the stag beetle Torynognathus chrysomelinus Bomans, 1986 were found inside the nests of Pseudolasius ants in Peninsular Malaysia. This paper provides a detailed description of T. chrysomelinus, which is the first ever record of myrmecophily in this genus and the third record in the family Lucanidae. This is also the first record of myrmecophilous Coleoptera with Pseudolasius ants as a host. The description includes the illustration of the male genitalia, mouthparts, larva, and pupa of this genus for the first time. Furthermore, the systematic position of T. chrysomelinus was inferred by the molecular phylogenetic analysis of the family Lucanidae. The results suggest that Torynognathus is a sister taxon to the genus Aegus.

Dorcus montivagus is a Japanese endemic stag beetle that feeds exclusively on dead beech wood, and its distribution is almost completely coincidental with that of beech forests. Japanese beech, Fagus crenata, is the dominant tree species of the cool-temperate deciduous broad-leaved forests in Japan. Historical changes in the distribution of beech forests due to Pleistocene climate change are expected to have also affected the phylogeographic structures of dependent beech-feeding phytophagous insects. In this study, we elucidated the present phylogeographic structures of D. montivagus using molecular markers, and also compared them with the present geographic genetic structures of beech tress and the post-glacial distribution as inferred by pollen fossil analyses. It was found that D. montivagus is largely differentiated into two phylogenetic clades: Clade I consisted of populations from Hokkaido, Honshu and Shikoku, and Clade II consisted only of Kyushu populations. Furthermore, the genetic diversity of the stag beetle showed a geographically declining gradient from south-west to north-east, consistent with the genetic variation observable in Japanese beech. Genetic differentiation between the Sea of Japan side and the Pacific Ocean side populations was also observed in both clades of the stag beetle. These results indicate a similar phylogeographic structure between the stag beetle and Japanese beech. Therefore, the distributional changes in Japanese beech correspondingly restricted the migratory dispersal of D. montivagus, and strongly influenced its phylogeographic structure.

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.