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The cryptic species that make up the Euwallacea fornicatus species complex can be readily distinguished via their DNA sequences. Until recently, it was believed that the Hawaiian Islands had been invaded by only one of these cryptic species, E. perbrevis (tea shot hole borer; TSHB). However, following the 2016 deposition of a DNA sequence in the public repository GenBank, it became evident that another species, E. fornicatus (polyphagous shot hole borer; PSHB), had been detected in macadamia orchards on Hawaiʻi Island (the Big Island). We surveyed the two most-populous islands of Hawaiʻi, Big Island and Oʻahu, and herein confirm that populations of TSHB and PSHB are established on both. Beetles were collected using a variety of techniques in macadamia orchards and natural areas. Individual specimens were identified to species using a high-resolution melt assay, described herein and validated by subsequent sequencing of specimens. It remains unclear how long each species has been present in the state, and while neither is currently recognized as causing serious economic or ecological damage in Hawaiʻi, the similarity of the newly-confirmed PSHB population to other damaging invasive PSHB populations around the world is discussed. Although the invasive PSHB populations in Hawaiʻi and California likely have different geographic origins within the beetle’s native range, they share identical Fusarium and Graphium fungal symbionts, neither of which have been isolated from PSHB in that native range.

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The Euwallacea fornicatus species complex (Coleoptera: Curculionidae: Scolytinae: Xyleborini) is a group of four cryptic ambrosia beetle species. Native to Asia, several members of the complex have invaded other continents, where they cause significant economic losses to agricultural crops (e.g., avocado) and natural ecosystems. We were primarily interested in developing management strategies by focusing on the flight behavior of the beetles. Thus, seasonal differences in flight activity were assessed using panel traps baited with a commercial quercivorol lure, placed in infested avocado orchards in Danei, Tainan, Taiwan. Same traps were used to investigate the flight activity of a natural enemy, an undescribed species of the Braconid genus Eucosmophorus sp. Shothole borer species were identified using a DNA-based, high resolution melting assay. Trap data were compared to the predictions of a simple degree-day model, incorporating developmental data and several environmental parameters known to influence flight. Such as the time period representing most of flight activity in a day and temperature-dependent flight propensity. In stark contrast to the degree-day model which predicted the highest emergence, and by extension flight, of shothole borers during spring and summer (May to November), flight activity was actually lowest during these months, and instead, peaked during the winter (October to March). Abundance of the parasitoid wasp closely mirrored flight activity of the shothole borers. The mismatch of trapping and modeling data can have many causes, heavy precipitation and possibly cooperative brood care may suppress the dispersal behavior of the shothole borers during the summer.

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