Description of the female of <i>Ceromya</i> <i>glaucescens</i> Tachi &amp; Shima (Diptera: Tachinidae) and discovery of unusual sexual dimorphism in this species.

Sexual dimorphism is a phenomenon in which the male and female of a species differ in features of the external morphology such as size, shape, colour, or the development of appendages. In the Diptera, stalked compound eyes, leg modifications and wing patterns are well-known examples of sexual dimorphism (McAlpine 1979; Zeil 1983; Adler & Adler 1991; Meyerrochow & Reid 1994; Wilkinson & Dodson 1996; Sivinski 1997; Baker & Wilkinson 2001; Eberhard 2002; Puniamoorthy et al. 2008). Males and females of sexually dimorphic species are often described as separate species due to the dissimilarity in external characters, thus leading to problems in identification and proper association of the sexes. In contrast to characters that are usually involved in sexual dimorphism, leg chaetotaxy is considered one of the invariable character systems, irrespective of sex, in the tribe Siphonini of the Tachinidae, and is thus widely used in keys to genera and species (O'Hara 1989; Andersen 1996). Species' identification by DNA barcoding has been used in various groups of organisms (Hebert et al. 2003; Ratnasingham & Hebert 2013). In insects, males, usually more easily identified by morphological characters (e.g., postabdominal features) than females, are often used for barcoding. The identification of females will improve as sequence data accumulate, such as data from pairs collected in copula. In this paper, I describe sexual dimorphism in the Japanese endemic species of tachinid fly Ceromya glaucescens Tachi & Shima, 2000 of the tribe Siphonini, and use molecular and morphological data for the identification of this species. Sequence data of C. silacea (Meigen, 1824) are also included for comparison.