Entomological Science最新文献

The sexually dimorphic dynastine centaurus beetle, genus Augosoma (Coleoptera: Scarabeidae), is endemic to tropical Africa where two species are found (A. centaurus and A. hippocrates). These beetles are consumed by rural populations, cause damage in plantations and are targets of insect collectors and traders. We present information on size differences and analyzed intersexual niche divergence and seasonality of A. centaurus in seven study sites in three West African countries (Ivory Coast, Togo and Nigeria). We recorded 711 light-attracted and/or opportunistically encountered individuals, as well as another 97 beetles in standardized transect surveys. In the latter, we found the adult sex ratio was equal, but was significantly skewed towards females in light-attracted and/or opportunistically encountered individuals. In a sample of 298 adult beetles, males were significantly larger than females, with almost no size overlap between sexes. Beetle activity was highly seasonal with most animals observed in November, active from 19:00 h to 24:00 h. Differences in habitat use were not significant between sexes, with most individuals observed in secondary forest. Males were found higher on vegetation than females and beetles of both sexes were found on Pandanus and raffia palms. Beetles were larger in sites with more vegetation cover, and there was a significant effect of tree species on body size of both sexes. Study area or country had no effect on any of the studied parameters. Our study confirms that transect surveys without light trapping can be an effective tool for understanding large-sized tropical beetles of similar ecological characteristics.

Many species of grasshoppers in subfamilies Oedipodinae, Gomphocerinae and Acridinae make sounds when they escape by flying. We carried out four kinds of experiments with the Chinese grasshopper, Acrida cinerea (Orthoptera: Acrididae: Acridinae), whose males often make sounds while flying, to examine the mechanism of sound production during flight by grasshoppers. First, we recorded high-speed video and audio of the tethered flight of the males and found that they produced sounds when they clapped their hindwings together at the end of the upstroke. Second, we recorded the tethered flights of the males when we prevented them from clapping their hindwings to clarify whether the hindwing clapping produced the sounds, and we found that the obstruction of clapping hindwings prevented sound production by the males. Third, we recorded the free flight of the males and determined whether the sound produced by clapping hindwings was not specific to the tethered condition. The males clapped their hindwings during free flight, and sounds were produced when they clapped their hindwings. Finally, we observed the tethered and free flights of the females because the possibility of crepitation flight by the females existed, and we found that sound was produced by females clapping their hindwings during flight. These results showed that male A. cinerea make sounds during flight by clapping their hindwings, and females also have the ability to make sounds by using the same mechanism. This study provides the first experimental evidence on the mechanism of sound production during flight through observing the behaviors of grasshoppers.

Phenology of insect abundance in less seasonal tropical regions is well recognized. Even in Bornean tropical forests in Malaysia, where there is no distinct dry season, there are insect species that behave as if their environments were highly seasonal. How such seasonal dynamics are shaped and what factors determine the seasonality remains largely unresolved. To elucidate the mechanisms underlying population dynamics in relatively stable tropical environments, we classified monthly samples collected with light traps at Lambir Hills National Park, Malaysia, and generated long-term time-series data for the family Passalidae (Coleoptera: Scarabaeoidea), which spend nearly their entire life cycle within or beneath decayed wood. Analyses of our data (20 species and 768 individuals) revealed that there were clear abundance peaks in April and October at the community level. We analyzed the data together with climate data using a nonlinear time-series analysis called convergent cross mapping. The causal relationship between adult population dynamics of the dominant species (Leptaulax planus) and temperature was detected, which shows that the population dynamics of L. planus are driven by cool temperatures approximately 1 month before emergence. Our study indicates that even in perpetually wet tropical rainforests in Southeast Asia, insect population dynamics respond to climatic factors and show seasonal population dynamics.

The aphid Colophina monstrifica forms woolly colonies with sterile soldiers on the secondary host Clematis uncinata in Taiwan. However, the gall or primary-host generation of C. monstrifica has not been found to date. We successfully induced galls of the species on Zelkova serrata by attaching its eggs to the trees, and also found a few naturally formed galls on another Z. serrata tree. The identity of the aphids was confirmed by examining their mitochondrial DNA sequences. First and second instar nymphs in the galls exhibited attacking behavior toward artificially introduced moth larvae. Observations with a scanning electron microscope revealed that the gall inner surface was densely covered with minute trichomes. This indicates the water repellency of the inner surface, and suggests that young nymphs of C. monstrifica dispose of honeydew globules outside the gall, as known in the congener Colophina clematis.

The effects of ovipositing female body size on the survival of the first and second offspring under self and conspecific superparasitism have not been determined. Here, we report the importance of the body size of ovipositing females for three intervals (0, 1, and 24 h) between first and second ovipositions using a semi-solitary ectoparasitoid, Echthrodelphax fairchildii, and fourth-instar nymphs of its host, the planthopper Laodelphax striatellus. We addressed the case in which the first and second parasitoid eggs were laid on different sides of the same host. The second ovipositing female killed the previous offspring using the sting, but when the oviposition intervals were 0 and 1 h, the elimination was unprofitable because both offspring often emerged under non-probing superparasitism. The survival rate of the second offspring decreased with increasing oviposition intervals under non-probing superparasitism, whereas that of the first offspring was independent of oviposition intervals. Under non-probing superparasitism, the survival rates of the first and second offspring were higher under conspecific superparasitism than under self superparasitism, especially when the first and/or second ovipositing females were small. Large mothers ensured high survival rates of their offspring under non-probing superparasitism, except the survival rate of the second offspring under conspecific superparasitism, which was negatively associated with the first female's size. Thus, the first offspring from small mothers were likely to lose the competition to the second offspring. Under probing superparasitism, the second offspring survival rate was positively associated with the mother's size, suggesting that offspring, not ovipositing females, release agents affecting the mother-size effect.

Evaluating the spatial genetic structure of rare species is important because it could provide information on the degree of habitat fragmentation and effective population size that are necessary for conservation planning. We examined the genetic structure of the grassland butterfly Plebejus argyrognomon that has severely declined in recent decades using single nucleotide polymorphisms obtained by the MIG-seq method. The study region was in the southern Ina Basin located in central Japan, where P. argyrognomon inhabits grasslands in agricultural field margin as well as in riverbank. We found a positive association between genetic and geographic distances, but the pattern was nonlinear, with little change in genetic distance above 12 km. The genetic differentiation was considerable, as demonstrated by F_ST and Structure. Moreover, genetic diversity was positively associated with habitat connectivity index, suggesting severe genetic drift in isolated populations. Comparing two habitat types, the genetic structure tended to be similar among agricultural field margin populations while dissimilar among riverbank populations, suggesting frequent gene flow in the former. Coupled with the presence of many habitat patches in agricultural field margin, we consider that agricultural field margin populations in the northern part of the study sites appear valuable to ensure long-term persistence of the regional P. argyrognomon population.

Planting of Japanese rose Rosa rugosa along the Baltic Sea coastline has contributed to the synanthropization of coastal ecosystems. Many ant species inhabiting coastal dunes are rare, have high conservation value and are sensitive to ecosystem disturbances. This short communication presents a study describing the species composition of ground-nesting ants beneath the invasive plant Rosa rugosa. Twenty-five paired invaded–native plots were established along the Hel Peninsula in gray and white dunes. We identified a total of 13 species within both the invaded and reference plots, of which 11 species were shared. The difference between reference and invaded plots was tested using permutational multivariate anova based on the Bray–Curtis index dissimilarity matrix. Permutational multivariate anova partitioning showed the greatest component was the residual, and there was no evidence for vegetation type effect. Thus, we did not confirm the negative influence of R. rugosa invasion on the community composition of ground-nesting ants. Comparing the species composition of invaded and reference plots, we identified a small bias towards a slightly higher frequency of hygrophilous Myrmica species and a higher frequency of the psammophilous ant Lasius psammophilus, which raises the question for future investigations of whether R. rugosa creates nesting microhabitats preferred by hygrophilous ants.

Juvenile mermithid nematodes were found to parasitize winged females (sexuparae) of Eriosoma auratum and Tetraneura radicicola. The morphological characteristics of mermithid nematodes are briefly described. The 18S rDNA and 28S rDNA obtained from one nematode were sequenced and used to construct a Bayesian phylogenetic tree, on which the host ranges of mermithid nematodes were represented. Our study indicated that mermithid parasitism of sexuparae led to fewer and smaller sexual female embryos. This is the first record of a mermithid in relation to eriosomatine aphids and the fourth record with respect to Aphididae.

For identification of insect larvae occurring in galls formed on culms of Sasa kurilensis in Shiga-kôgen, Nagano and those of Pseudosasa japonica in Takao-san, Tokyo, we undertook a DNA barcoding analysis using the mitochondrial cytochrome oxidase subunit 1 (CO1) gene. Seventeen operational taxonomic units (OTUs) were identified for larvae from Shiga-kôgen and one for those from Takao-san. Of 17 OTUs from Shiga-kôgen, 10 were most likely assigned to Cecidomyiidae (Diptera), one to Anthomyzidae (Diptera), two to Lepidoptera and four to Hymenoptera. One OTU from Takao-san was assigned in the Cecidomyiidae cluster. However, none of the OTUs was assigned to known species. It is unknown whether primary gall-makers are included in the putative cecidomyiid, anthomyzid and lepidopteran species found in this study. However, hymenopteran species occurring in these galls would be parasitoids. How so many cecidomyiid species coexist on bamboo culms in Shiga-kôgen is an interesting issue and remains to be resolved.

Omnivory is a feeding habit in which animals prey on organisms from two or more trophic levels. Omnivorous species play important roles in predator–prey interactions, food web dynamics, and ecosystem functions. Although cricket species have been considered omnivores, quantified investigations of their feeding habits have not been carried out. Therefore, we compared the developmental time, body size and mortality rate of the band-legged ground cricket, Dianemobius nigrofasciatus (Matsumura) (Orthoptera: Trigonidiidae) reared on diets meant for carnivores and herbivores. Furthermore, to examine whether the crickets can balance their nutritional conditions through their food choices, we set up two additional diet treatments, which comprised diets for carnivores and herbivores provided simultaneously or by rotation. The mortality rate of the carnivore diet treatment was higher than that of the other diet treatments. This result suggests that D. nigrofasciatus is a “herbivore” that also obtains nutrients from resources other than plant materials. Although developmental time did not significantly differ among the dietary treatments, the body size of the crickets that were provided both diets simultaneously was significantly larger than that of the crickets provided with only the diets for either carnivores or herbivores. These results suggest that an appropriate amount of carnivorous feeding is advantageous for the development of the cricket, and indicates that crickets can balance nutrition on their own.