X‐ray microtomography has been applied successfully to obtain reliable microstructural information of many insect species. Nonetheless, the technique has not been widely applied to ambrosia beetles. The ambrosia beetle Euwallacea interjectus (Blandford) was first recorded as a vector of plant pathogenic fungus Ceratocystis ficicola Kajitani & Masuya, which has caused serious wilt disease in many fig orchards in Japan since 1999. Previous studies of E. interjectus have not described the mycangia (fungus‐storing organ) in detail. In this study, we non‐destructively examined the internal structure of an adult female of E. interjectus through computed microtomography scans. Paired mycangia were observed on typical computed tomography cross‐sections of the head. Each mycangium, ovoid in shape, was located in tissues just posterior to emarginated notch of eyes, adjacent to pharynx. Three dimensions (length × width × depth) of the mycangia were measured on stereography. We confirmed the absence of mycangia in the other body parts, such as elytra, prothorax and coxa of legs.

Ficus carica plantations in Japan were first reported to be infested by an ambrosia beetle species, identified as Euwallacea interjectus, in 1996. The purpose of this study was to determine the symbiotic fungi of female adults of E. interjectus emerging from F. carica trees infected with fig wilt disease (FWD). Dispersal adults (51 females) of E. interjectus, which were collected from logs of an infested fig tree in Hiroshima Prefecture, Western Japan, were separated into three respective body parts (head, thorax, and abdomen) and used for fungal isolation. Isolated fungi were identified based on the morphological characteristics and DNA sequence data. Over 13 species of associated fungi were detected, of which a specific fungus, Fusarium kuroshium, was dominant in female head (including oral mycangia). The plant-pathogenic fungus of FWD, Ceratocystis ficicola, was not observed within any body parts of E. interjectus. We further discussed the relationship among E. interjectus and its associated fungi in fig tree.

Earwigs (Dermaptera), such as Forficula auricularia L., are important euryphagous predators for a wide variety of prey and can markedly influence the populations of orchard pests. Most previous studies on earwig feeding behaviour have not used adult beetles of the prey species; few researchers have focused on prey preference in earwigs. Some fragments of beetle exoskeleton and an earwig adult, Anisolabella marginalis (Dohrn), were found in the same cage, where adults of ambrosia beetle, Euwallacea interjectus (Blandford), were emerging from the logs of a fig tree infected with Ceratocystis canker (fig wilt disease). Thus, A. marginalis was suspected of being a predator of E. interjectus. To shed light on this issue, in the laboratory, we set up a test arena and observed and recorded behavioural interactions between A. marginalis and E. interjectus. E. interjectus was collected from the logs of fig trees and reared on an artificial diet, along with six different ambrosia beetle species, which were collected from a trap (baited with ethanol) and a fallen maple tree. A series of laboratory experiments demonstrated that A. marginalis is actually a predator of E. interjectus and other species of ambrosia beetle, indicating its a potential for use in effective pest control in the field. The predators frequently consume and tend to select their prey depending on prey size, rather than sex and beetle species. Furthermore, earwigs have alternative predatory strategies for dealing with seven different species, although they use their forceps to cut the body of most tested beetles.

The red-haired pine bark beetle, Hylurgus ligniperda (Fabricius), is one of the most rapidly spreading invasive forest insects. Originally from Eurasia, it has subsequently been introduced to Oceania, North, and South America. Yet, the status of H. ligniperda in East Asia is ambiguous. Here, investigation and analysis were conducted on the beetle in China, South Korea, and Japan. New occurrences in China and South Korea were recorded by field surveys and the expansion of H. ligniperda spreading in East Asia was analyzed. The results show that H. ligniperda is likely an invasive species in East Asia, initially invading Japan, then South Korea. Now it has invaded and successfully colonized Shandong province, China. Furthermore, the species has spread rapidly and it is now widely distributed in South Korea and Japan.

Ambrosia beetles bore into host trees, and live with fungi symbiotically that serve as a food source. However, it is challenging to directly observe these beetles in the wild. In this study, Euwallacea interjectus Blandford (Coleoptera: Curculionidae: Scolytinae), a pest of fig trees in Japan, were reared under artificial conditions to emulate the behavior of Ambrosia beetle. Fungi were isolated from the adult females of E. interjectus to identify the species associated with secondary symbiosis. In total, nine filamentous fungi and one yeast were identified using morphological characteristics and DNA sequence data. Neocosmospora metavorans (Hypocreales: Nectriaceae), Fusarium sp. (Hypocreales: Nectriaceae), that is undescribed, and Meyerozyma guilliermondii (Saccharomycetes: Saccharomycetales) (yeast) were isolated more frequently from the head (including from mycangia, the fungus-carrying organ) than from the thorax and abdomen of adult beetles. Neocosmospora metavorans was the dominant species isolated from 12 out of 16 heads at 200 to 3300 CFUs/head, compared to the primary mycangia fungus from wild beetles, i.e., Fusarium kuroshium (Hypocreales: Nectriaceae). Temperature had a marked effect on fungal growth in the three symbiont species. Our results represent a major paradigm shift in understanding beetle–fungal interactions, as they show specific symbiont switching can occur in different nesting places.