Leptoconops (Styloconops) myersi (Tonnoir, 1924) (Diptera: Ceratopogonidae) revealed as the causal agent of "Hot Water Beach rash"

The causal agent for a commonly reported rash associated with bites by small insects on various Coromandel Peninsula beaches is confirmed as Leptoconops myersi. The taxonomy, biology and medical significance of this species are briefly reviewed. The rash is of unknown medical importance, and this species is not known or implicated to be involved in the transmission of any pathogens. Commentary Residents and visitors of various Coromandel Peninsula beaches have intermittently, but not uncommonly, reported to MAF and health professionals a vivid rash following episodes of biting by small unidentified insects. Most, if not all, of the entomologists involved have assumed the biting insect to be the native ceratopogonid, Leptoconops myersi (coastal biting midge). The pestiferous biting of humans by this fly of only 1.15 mm wing span has long been known, and was exquisitely reported by Tonnoir in his original description of the species in 1924 (as Acanthoconops myersi). However, the association between Leptoconops myersi and the aforementioned rash appears to have been hitherto merely subjective. This is believed to be the first case where both the rash and the conclusive identification of causal agent have been catalogued. In early December 2006 the MAF Plant Health and Environment laboratory was notified of a moderate rash suffered by a fisherman after being bitten by tiny insects at Colville Beach (CL). An image of moderate rash was submitted (Fig. 1 itchy and scratchy), along with a single damaged female ceratopogonid that had been “collected” biting the rash victim. As the insect had been “collected” using the common “hard smack” method, the sample resembled a 1.2 mm 2 two-dimensional, mangled jigsaw puzzle, and thus was not suitable for slide mounting, as is required for authoritative morphological ID of this family. The sample was given the interim ID of “almost certainly Leptoconops myersi” but the ID was not able to be conclusively determined.