Taxonomic review and distribution of giant water bugs (Hemiptera: Belostomatidae: Lethocerinae) in the Palearctic,Oriental, and Australian regions

The aim of the present study was to analyze the morphology and COI sequences of giant water bugs (Belostomatidae: Lethocerinae) that inhabit the Palearctic, Oriental, and Australian regions (i.e., three Lethocerus and a single Kirkaldyia species). Analysis revealed that both L. patruelis and L. indicus share two light stripes on the pronotum, but L. patruelis possesses narrower stripes and L. insulanus possesses an additional longitudinal narrow dark median band, whereas K. deyrolli was characterized by not having such markings. With regards to genetic analysis, the average intraspecific genetic distances of L. patruelis and L. indicus (from Palearctic and Oriental regions are 0.3 and 0.8%, respectively), but K. deyrolli which was collected from Northeast Asia, showed much higher intraspecific genetic distance (3.7%). The genetic distance between Kirkaldyia and Lethocerus (16.4–16.8%) is similar to that found between the genera of other hemipteran taxa. This study also newly reported the extended easternmost distribution of L. patruelis up to Surat Thani Province in southern Thailand. Along with K. deyrolli, which is considered threatened in South Korea and Japan, Lethocerus species have been facing threats in Southeast Asia, where they are heavily harvested and commonly sold in local markets as food. Therefore, future conservation efforts should be directed toward Lethocerus species in tropical Southeast Asia, especially the rarely found L. patruelis.     

Relationships between predatory aquatic insects and mosquito larvae in residential areas in northern Thailand

In order to elucidate the poorly understood relationships between mosquito larvae and their predatory aquatic insects in urban and suburban areas of tropical Southeast Asia, where vector‐borne diseases are prevalent, aquatic insects were sampled from 14 aquatic habitats in residential areas of Chiang Mai, northern Thailand, during the rainy season (July to November) in 2016. Correlations among biological variables, densities of major predatory aquatic insect groups (i.e., Odonata, Coleoptera, and Hemiptera: OCH group) in wetlands and artificial lentic habitats, and the density of mosquito larvae were analyzed. Among the sampled mosquito larvae, Culex spp. were the most abundant, and both OCH density and water quality were major determinants of Culex spp. density (r_s = ?0.302 and ?0.396, respectively). Logistic regression analyses indicated that the probability of Culex spp. occurrence was significantly and negatively correlated with OCH density. Furthermore, high macrophyte abundance was associated with higher predator density, potentially reducing mosquito density. Hemipteran predators were most negatively correlated with Culex spp. density, regardless of whether macrophyte abundance was high or low (r_s = ?0.547 and ?0.533, respectively). Therefore, hemipteran predators were the most important aquatic insect predators in the urban and suburban residential areas of Chiang Mai, Thailand, and OCH species, such as the hemipteran Micronecta scutellaris, could be used as biological control agents against mosquitoes in the region.