Entomological Science最新文献

Meimuna opalifera males emit extremely complex calling songs, with the main section comprising two parts. To investigate whether these two parts of the calling song have different meanings for the receivers, we conducted playback experiments. We counted and compared the number of response calls when different types of sound stimuli were presented under laboratory conditions. Meimuna opalifera males emitted significantly greater response calls during the playback of stimuli containing the former part of the songs than those containing the latter part only. This suggests that M. opalifera males tend to respond by detecting characteristics in the former part of the songs. Because the peak frequencies were similar between the former and the latter parts, the temporal patterns of the songs might be important in short-range communication between males of M. opalifera.

The survivorship of social insects is known to increase with group size, even in situations of stress, such as starvation and exposure to insecticides. However, in termites, studies have been undertaken only with workers, disregarding the possible effect of soldiers. The role of soldiers in the termite colonies goes beyond defense, mainly in Nasutitermes species. It is already known that soldiers initiate the foraging as well as improve the decision-making of food resources. Here, we evaluated the effect of group size and the presence of soldiers on exposure to sublethal doses of the insecticide imidacloprid in Nasutitermes corniger (Termitidae: Nasutitermitinae). To do so, toxicity bioassays were undertaken initially to determine the dose of the insecticide required to kill 50% of the N. corniger population (LD₅₀) to be used in the main experiments. Survival bioassays were then carried out with termite groups, with and without soldiers, in different sizes (6, 10, 14, 22, 26, 30 and 60), exposed and nonexposed to insecticide. In general, the mean time to death of termites increases linearly with group size. However, the mean time to death in groups with soldiers was significantly longer only in groups exposed to the insecticide. Our results indicate that soldiers can help to increase the tolerance of nasute termite groups to insecticides, in addition to the group size, as already shown in the previous study. The size of the group and social context could, therefore, modulate behavioral and/or physiological responses that enhance the ability to survive under stressful situations.

Wetland biodiversity is currently declining on a global scale. Wetland biodiversity understanding is critical for determining the wetlands' conservation value. In this study, Macroplea Samouelle, 1819 (Coleoptera: Chrysomelidae) was discovered in Aomori Prefecture, Honshu Island, Japan. Only two Macroplea species have been recorded in Japan, M. japana (Jacoby, 1885) and M. mutica (Fabricius, 1792). Macroplea japana had been unrecorded for 60 years before being rediscovered in Honshu Island in 2022, and a single adult M. mutica female was discovered in Hokkaido Prefecture in 2003. The discovered individuals were concluded to be M. mutica based on morphological and molecular analyses. Although morphological differences were observed with the Eurasian M. mutica individuals, the male genitalia was nearly identical to M. mutica. For the molecular phylogenetic analysis based on COI and 28S sequences, Macroplea individuals in Japan were clustered with M. mutica on the Eurasian Continent. This is the first record of this species on Honshu Island (and the second in Japan), as well as the first record of adult males. This species would require conservation policies and additional distributional surveys.

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.