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Myrmecophytes of the genus Macaranga (Euphorbiaceae) have symbiotic relationships with specific ant species in which ants protect the host plant from herbivores. The intensity of such anti-herbivore defenses elicited by symbiotic ants has been shown to decline with the increase in tree size during tree growth and drastically decrease with various types of disturbances, such as tree falls and ant predation during tree growth. These decreases in anti-herbivore defense during tree growth may cause differences in host plant utilization among leaf-chewing lepidopteran species that vary in the degree of development of myrmecophilous traits. In this study, to test this hypothesis, we determined the interspecific differences in host plant use response to tree size variation and the absence or presence of symbiotic ants among three dominant leaf-chewing lepidopteran species, a myrmecophilous species (Arhopala amphimuta), and two non-myrmecophilous species (Shafferiella macarangae and Aetholix flavibasalis) feeding on a Macaranga myrmecophyte species, M. bancana, in a primary forest in Borneo. The results showed that there were significant differences in the responses to the absence or presence of symbiotic ants and tree size among the three lepidopteran species. The literature has suggested that the larvae of myrmecophilous species prefer trees with symbiotic ants. Although larvae of the non-myrmecophilous S. macarangae were found on trees with and without symbiotic ants, the moth species may prefer trees with weak anti-herbivore defense intensity. We identified another non-myrmecophilous species, A. flavibasalis, that used M. bancana trees as host plants only when symbiotic ants were no longer present on the trees. These results support our hypothesis and suggest that changes in anti-herbivore defense intensity associated with the growth of Macaranga myrmecophytes have a strong influence on host plant usage by lepidopteran leaf chewers. [ABSTRACT FROM AUTHOR]

Given the high-level physiological functions and nutrient concentrations of bark that cover the entire trunks of huge trees, research into bark nutrient traits and the development of models that estimate the bark biomass of tropical trees is essential when it is sought to understand forest nutrient cycling and tree ecological traits. This study investigated the concentrations of six bark nutrients (nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sodium (Na)) by individual tree size and the soil nutrient concentrations for two major pioneer species (Macaranga gigantea and M. hosei) of Malaysia. To estimate bark biomass, allometric equations using tree diameter, height, and crown diameter were developed by combining previous data from adjacent forests with the present data. We found no significant relationship between tree size and most bark nutrient concentrations, though all nutrient concentrations of the two pioneer trees were significantly higher than those of primary forest tree species. Surprisingly, no relationship was found between the soil and bark nutrient concentrations for either species. All the size parameters used in the allometric equations accurately estimated bark biomass. There were no differences in equations between the two species when diameter served as an explanatory variable, but differences were apparent when height and crown diameter were so used. A comparison of allometric equations that yielded the bark biomasses of different types of forest showed that the bark biomass of the tropical secondary forest trees was less than half of that of tropical dry forest trees of the same diameter. Thus, the use of inappropriate equations and nutrient concentrations increases the possibility of serious errors in estimating bark biomass and forest nutrient cycles. [ABSTRACT FROM AUTHOR]

Myrmecophytes have mutualistic relationships with symbiotic ants. Although myrmecophytic Macaranga (Malpighiales: Euphorbiaceae) species are well protected by aggressive Crematogaster (Hymenoptera: Formicidae) ants, some bug species occur on the myrmecophytes. To clarify the associations of these bugs with the plants and the ants, we studied the food habits of 3 bug species, Pilophorus lambirensis Nakatani et Komatsu, 2013 (Hemiptera: Miridae: Phylinae), Phylinae sp. 1, and Arbela sp. 1 (Hemiptera: Nabidae). We conducted field observations in a Bornean rainforest. First, we located these bugs and studied their behavioral responses to the ants on Macaranga species; we then conducted stable isotope analyses. All bugs avoided direct contact with ants, but they occurred only on trees with active ants. Pilophorus lambirensis and Phylinae sp. 1 were most commonly observed on the apical parts of host trees, whereas Arbela sp. 1 was mainly in areas distant from the apical parts where ants were sparse. The stable isotope ratios indicated that Phylinae sp. 1 fed on food bodies, which are nutrient-rich spherical bodies produced by Macaranga trees on the apical parts for ants. Although the main diet of the other 2 species remains unclear, nitrogen isotopic signatures demonstrated that P. lambirensis is herbivorous, whereas Arbela sp. 1 is carnivorous. However, the distant location from ants and its isotopic signatures indicated that Arbela sp. 1 rarely fed on the ants. At least 2 mirid bug species might obtain enemy-free space in addition to the food provided by the myrmecophytes. [ABSTRACT FROM AUTHOR]

A recent molecular phylogeny of the genus Crematogaster reclassified some members of the former subgenera Paracrema and Physocrema into the C. inflata -group, now comprised of five species: C. ampullaris , C. inflata , C. modiglianii , C. onusta and C. subcircularis. Here, a molecular analysis of the Crematogaster inflata -group and eight other species of the former subgenus Physocrema (C. aurita , C. difformis , C. mucronata , C. physothorax , C. sewardi , C. tanakai , C. vacca and C. yamanei) is conducted using a total of c. 4 kb of sequence data from six nuclear protein-coding genes and two mitochondrial genes. Monophyly of the C. inflata -group is strongly supported. A revised morphological delineation of the subgroups is proposed, supported by the molecular phylogeny: three morphologically distinct subgroups, the C. difformis -subgroup, the C. vacca -subgroup and the C. inflata -subgroup. Molecular dating and biogeographical analyses indicate that the C. inflata -group originated in the Sundaic region around the Middle Miocene 12 Mya and diversified from the Late Miocene to Pliocene. Ancestral state reconstructions indicate that the C. inflata -group diversified from an ancestor with a swollen propodeum and circular-shaped metapleural gland opening. Biogeographical reconstruction indicates that dispersal to peripheral areas and allopatry due to sea-level changes shaped the evolutionary history of the C. inflata -group. [ABSTRACT FROM AUTHOR]

Lithosiini (Lepidoptera: Erebidae: Arctiinae) is distinctive in having some species that feed on lichens, whereas the majority of moths feed on vascular plants. However, the larval diet of most Lithosiini species is poorly known. This study examines whether Lithosiini species, collected in a tropical rainforest of Borneo (nine species) and a temperate forest of Japan (eight species), feed on lichens as larvae, based on stable isotope analyses. As a result, the δ15N values for eight of nine Lithosiini species collected from Borneo were notably lower than those of nine co‐occurring herbivorous non‐Lithosiini species, and were similar to those of sympatric, lichen‐feeding termites; however, δ13C and δ15N values of one Lithosiini species (Adites sp.) were significantly higher than those of the other moth species and similar to those of humus‐feeding termites and predatory insects occurring at the same site. These results have suggested that the Lithosiini in the Southeast Asian tropical rainforests contain some species that feed on lichens as their larval main diet and at least one species whose larvae feed on humus or animal‐derived materials. In contrast, the δ13C and δ15N values of all examined Lithosiini species (eight species) in the temperate forest have suggested that their larvae fed on plants and not on lichens. Our stable isotope ratio analysis presented quantitative evidence suggesting lichen‐feeding by Lithosiini moths in a tropical rainforest without observation of feeding behavior during the larval stages. [ABSTRACT FROM AUTHOR]

Aetius bicuspidatus sp. nov. (Araneae: Corinnidae) is described here on the basis of male and female specimens collected from the Lambir Hills National Park, Sarawak, Borneo. The posterior carapace is elongated with bicuspid edge in both male and female. This character condition is very unique among Aetius species. [ABSTRACT FROM AUTHOR]

Tropical forest canopies are home to an extremely high diversity of arthropods, but their diversity, abundance, and community structures remain incomplete. Three species of oribatid mites from the crown leaves petioles of Light Red Meranti (Shorea quadrinervis Sloot), a tree species that is endemic to Borneo Island, are reported in the present study. A new species of Birobates (Oripodidae) is proposed, with a diagnostic key to adults of all known species of the genus worldwide. Dometorina plantivaga (Berlese, 1895) (Scheloribatidae) and Paralamellobates misella (Berlese, 1910) (Punctoribatidae) are reported for the first time from Borneo, and supplementary descriptions of those species are provided. Aspects of the distribution and habitat ecology of each species reported are discussed. [ABSTRACT FROM AUTHOR]

The seeds of dipterocarp trees are the main food resources for many species of weevils, bark beetles and small moths; however, for most seed-eating insects on dipterocarp tropical trees, seed utilization patterns remain poorly investigated. This study aimed to determine the fruit maturation stages at which eggs are laid by different insect seed predators feeding on the seeds or fruits of the following five dipterocarp species: Dipterocarpus globosus, Dryobalanops aromatica, Shorea beccariana, S. acuta and S. curtisii, which reproduced during the same period. We investigated the occurrence frequencies of the insect seed predators at various growth stages by collecting both unfallen and fallen fruit on several occasions during the period of seed/fruit maturation in a tropical rainforest in Borneo from September to December 2013. Weevils and bark beetles were the dominant insect seed predators of the five tree species. One or two weevil species of Alcidodes, Damnux and/or Nanophyes preyed on the seeds of each of the five tree species, and one bark beetle species, Coccotrypes gedeanus, preyed on the seeds of all five tree species. Many larvae, pupae and adults of each weevil species were found in pre-dispersal (unfallen) fruit, whereas bark beetles at various growth stages were found in post-dispersal (fallen) fruit. These results suggested that, among the dominant insect seed predators of the five dipterocarp species, weevil species oviposit on pre-dispersal fruit and begin their larval growth before seed dispersal, whereas the oviposition and larval development of bark beetle species occurs in post-dispersal fruit. [ABSTRACT FROM AUTHOR]

• We developed a new technique for dating aseasonal tropical secondary forests. • Tree age of the largest individual on each plot was measured using wood core Δ14C. • Estimating the duration after deforestation from Δ14C and time-series satellite data. • Significant relationship was observed between the two estimated forest ages. • Δ14C dating enables us to accurately estimate forest age within 60 years' duration. Following the widespread loss and degradation of old-growth forests throughout the tropics, the area of secondary forests has expanded significantly in the past few decades. Understanding the history of vegetation modification is necessary for the proper maintenance and management of tropical secondary forests. Although satellite image analysis is an effective method for evaluating such changes, observations in tropical regions are limited by dense cloud coverage, and it is difficult to estimate the timings of forest disturbances based on annual rings because the climate is aseasonal and trees do not form clear annual rings near the equator in Southeast Asia. In this study, we developed a new, highly accurate technique for dating tropical secondary forests after disturbances such as shifting cultivation and forest fire in Malaysia based on Δ14C content of trees. We established 29 plots (20 m × 20 m) in secondary forests in six areas of Malaysia, mainly in Sarawak, and used time-series satellite images to determine the most recent disturbance with temporal accuracy of <6 years. We collected wood core samples from one or two trees with the largest diameter in each plot and measured the Δ14C content of their pith to estimate tree ages. We detected a significant positive correlation between tree age estimated by Δ14C dating and the period since the latest disturbance according to the time-series satellite images. The Δ14C-based age estimates were approximately five years younger than those obtained by satellite image dating. This difference is considered to indicate the time required for land use shifts after clear cutting or forest fire, and for tree species invasion after land abandonment. Together, our results revealed that the Δ14C method may be used to date tropical secondary forests after disturbance with high accuracy, even in aseasonal tropical rainforest areas. [ABSTRACT FROM AUTHOR]

The genus Yunodorylus comprises four named species known exclusively from the Indo-Chinese and Indo-Malayan subregions. The queen and male of the genus were unknown until recently. However, the subdichtadiigyne was firstly discovered from two colonies of Y. eguchii (Borowiec, 2009), and described by Eguchi et al. in 2016. Then, the present authors discovered a colony of Yunodorylus doryloides (Borowiec, 2009) with a subdichthadiigyne and herein describe the subdichthadiigyne. The subdichtadiigyne of Y. doryloides is morphologically similar to that of Y. eguchii, but it can be distinguished by the combination of the following morphological characters: mandible elongate and slender, with the edge behind the basalmost tooth of the masticatory margin almost straight; lateroclypeal teeth rounded; mesosoma in dorsal view slenderer in the former than in the latter; mesonotum in dorsal view distinctly longer than broad in the former, but almost as long as broad in the latter; anterior margin of mesopleuron without a small lobe; metanotal groove in dorsal view faintly recognized; ventral margin of metapleuron almost straight; petiole in dorsal view narrower and longer in the former than in the latter; pygidium apically without any specialized setae. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

There are very few studies that have investigated host-specificity among tropical herbivorous insects. Indeed, most of the trophic interactions of herbivorous insects in Southeast Asian tropical rainforests remain unknown, and whether polyphagous feeding is common in the herbivores of this ecosystem has not been determined. The present study employed DNA bar coding to reveal the trophic associations of adult leaf-chewing chrysomelid beetles in a Bornean rainforest. Plant material ingested by the adults was retrieved from the bodies of the insects, and a portion of the chloroplast rbcL sequence was then amplified from this material. The plants were identified at the family level using an existing reference database of chloroplast DNA. Our DNA-based diet analysis of eleven chrysomelid species successfully identified their host plant families and indicated that five beetle species fed on more than two families within the angiosperms, and four species fed on several families of gymnosperms and/or ferns together with multiple angiosperm families. These findings suggest that generalist chrysomelid beetles associated with ecologically and taxonomically distant plants constitute a part of the plant-insect network of the Bornean rainforest. [ABSTRACT FROM AUTHOR]

The genus Utivarachna Kishida, 1940 currently comprises 23 species, with eight described from Borneo. We examined the type materials of the Bornean species, except for U. fukasawana Kishida, 1940, as well as newly collected specimens. As a result, we describe a new species, Utivarachna itiokai sp. nov., which belongs to the dusun-group. We also provide the first description of the female of Utivarachna ichneumon and redescribe the known Utivarachna species of Borneo.

The zeylanica group is one of the six species groups of the anthophilic genus Colocasiomyia de Meijere in the family Drosophilidae. In addition to two known species, five morphospecies have been recognized as members of this species group but left undescribed formally. In this study, species delimitation of these putatively new species was determined by barcoding of the mitochondrial COI (cytochrome c oxydase subunit I) gene and morphological comparison. Phylogenetic relationships within the genus Colocasiomyia were inferred by a cladistic analysis of 89 morphological characters. Based on the results of these analyses, we redefined the zeylanica species group and established two subgroups within it: the zeylanica subgroup comprised of C. zeylanica, C. nepalensis, C. pinangae sp. nov., C. besaris sp. nov. and C. luciphila sp. nov., and the oligochaeta subgroup of C. oligochaeta sp. nov. and C. grimaldii sp. nov. In addition, we briefly address the anthophilic habits of drosophilid flies using palm (Arecaceae) inflorescences, especially of the zeylanica group, compiling scattered collection records from the Oriental and Papuan regions.

The phylogeny of the Colocasiomyia cristata species group is reconstructed as a hypothesis, based on DNA sequences of two mitochondrial and six nuclear genes and 51 morphological characters. The resulting tree splits this species group into two clades, one of which corresponds to the colocasiae subgroup. Therefore, a new species subgroup named as the cristata subgroup is established for the other clade. Within the cristata subgroup, three subclades are recognized and each of them is defined as a species complex: the cristata complex composed of five species (including three new ones: C. kinabaluana sp. nov., C. kotana sp. nov. and C. matthewsi sp. nov.), the sabahana complex of two species (C. sabahana sp. nov. and C. sarawakana sp. nov.), and the xenalocasiae complex of five species (including C. sumatrana sp. nov. and C. leucocasiae sp. nov.). There are, however, three new species (C. ecornuta sp. nov., C. grandis sp. nov. and C. vieti sp. nov.) not assigned to any species complex. In addition, breeding habits are described for four cristata-subgroup species, each of which monopolizes its specific host plant. And, data of host-plant use are compiled for all species of the cristata group from records at various localities in the Oriental and Papuan regions. The evolution of host-plant selection and sharing modes is considered by mapping host-plant genera of each species on the phylogenetic tree resulting from the present study.

The genus Myrmarachne MacLeay, 1839 (Araneae: Salticidae) is one of the most diversified salticid groups in Southeast Asia, with 23 species previously recorded from Borneo. Based on the collections accumulated from 2004 to 2014 in the Lambir Hills National Park, we herein describe six new species: M. amabilis sp. nov., M. hashimotoi sp. nov., M. lagarosoma sp. nov., M. leptosoma sp. nov., M. salaputium sp. nov. and M. tintinnabulum sp. nov. In addition, we describe the female of M. endoi Yamasaki Ahmad, 2013 for the first time. The male-female combination in M. amabilis sp. nov., M. tintinnabulum sp. nov. and M. endoi were confirmed by DNA barcoding.

We describe a gall midge Macarangamyia itiokai Elsayed Tokuda gen. n., sp. n. belonging to the subtribe Schizomyiina (Diptera: Cecidomyiidae: Asphondyliini) inducing petiole galls on Macaranga bancana (Miq.) in Lambir Hills National Park, Borneo, Malaysia. The new genus is distinguishable from all known genera of Schizomyiina by the unique dorsally-placed aedeagus slit, the short, membranous, protrusible ovipositor, with scattered strong setae ventrally and dorsally, and the presence of spiracles on all larval thoracic segments. It is compared and separated from its closely related Oriental genera of Schizomyiina.