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1 June 2014 Sexual Dimorphism in North American Coccinellids: Sexing Methods for Species of Coccinella L. (Coleoptera: Coccinellidae) and Implications for Conservation Research
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Abstract

Coccinellids typically do not show exaggerated sexual dimorphisms, and the only reliable sexing methods for some species have been dissection and behavioral observations. Behavioral methods can potentially lead to sex identification but are very time consuming, require exposing sexually naïve individuals to conspecifics, and risk incorrect identification since homosexual mounting in these species has been observed in the laboratory. Research involving use of live specimens requires techniques to non-invasively determine the sex of individuals, but such methods have not been clearly or fully described in the literature. Closer examination of the species Coccinella novemnotata Herbst, Coccinella septempunctata L., Coccinella transversoguttata richardsoni Brown, and Coccinella trifasciata perplexa Mulsant has led to the discovery of a reliable and efficient way to differentiate the sexes by looking at the shape of the seventh sternite (fifth visible), and this method has been demonstrated to be 100% reliable for all four species. Another, even more rapid, method uses the shape of a prominent black pronotal marking and shows promise for C. novemnotata but is not applicable to the other species. Additionally, most species of Coccinella L. have males with conspicuous pale anterior coxal spots and femoral stripes that can be easily viewed, especially on mobile specimens. Morphometric data that quantify external dimorphisms and provide evidence for the reliability of using them for sexing are reported. All known external characters that can be used for sexing North American Coccinella species are consolidated for easy reference. The significance of these findings for research into the decline of native Coccinella species in the United States is discussed.

Leo Stellwag and John E. Losey "Sexual Dimorphism in North American Coccinellids: Sexing Methods for Species of Coccinella L. (Coleoptera: Coccinellidae) and Implications for Conservation Research," The Coleopterists Bulletin 68(2), 271-281, (1 June 2014). https://doi.org/10.1649/0010-065X-68.2.271
Received: 29 August 2013; Accepted: 21 March 2014; Published: 1 June 2014
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