Under its junior synonymsNycterosea brunneipennis and Geometra fluviata, the gem is the type species of generaNycterosea and Percnoptilota, respectively. The latter is treated as junior synonym of the former, but Nycterosea, though usually included in Orthonama these days, may warrant recognition as an independent genus after all.[2]
Description and ecology
female. British Columbia
The adult's wingspan is 18–21mm (0.71–0.83in); in their core range (e.g. Belgium and the Netherlands) they can be seen between April[citation needed] and November, but in outlying regions they may only be regularly encountered in late summer and early autumn, when vagrant individuals abound. This species is strongly sexually dimorphic: Males are light brown with a wavy pattern of whitish lines and a broad darker band running across the wings, forming concentric semicircles when the moth is at rest. There is a small whitish-rimmed black spot within the darker band between the centre and the leading edge of each forewing. The females are slightly larger and much darker, almost uniformly blackish brown with an indistinct lighter pattern and a forewing spot like the males have.[3]
Figs 2, 2a, 2b, 2c, 2d, 2e larvae in various stagesThe Gem - Hodges#7414 (Orthonama obstipata)
Adult caterpillars are greenish or brownish coloured and slightly tapered towards the head. The sides are yellowish, from the middle body segments light, dark-lined diamond spots which are black cored stand out.[citation needed]
Similar species
Due to the very characteristic wing drawing, the female moths are unmistakable. In the males there is a distant resemblance to grey-brown specimens of Xanthorhoe designata. In X. designata the midfield is, though, predominantly reddish-brown and bounded by a narrow black band.[citation needed]
The widespread, strongly sexually dimorphic and somewhat phenotypically variable gem has been described anew time and again by various authors, even as late as the early 20th century, but all these supposedly distinct taxa are nowadays considered to refer to a single species. Junior synonyms of the gem include:[5]
↑ Kimber [2010], and see references in Savela (2001)
↑ Pitkin & Jenkins (2004ab), and see references in Savela (2002)
Related Research Articles
Idaea, sometimes called Hyriogona, is a large genus of geometer moths. It was erected by Georg Friedrich Treitschke in 1825. They are found nearly worldwide, with many native to the Mediterranean, the African savannas, and the deserts of western Asia.
Eulithis is a Holarctic genus of moths in the family Geometridae erected by Jacob Hübner in 1821.
Orthonama is a genus of the geometer moth family (Geometridae). It belongs to the tribe Xanthorhoini of the "carpet" subfamily (Larentiinae). Nycterosea is usually included here by modern authors, but may in fact be distinct enough to warrant recognition as an independent genus. The genus was erected by Jacob Hübner in 1825.
Achroia is a genus of small moths of the snout moth family (Pyralidae). It belongs to the tribe Galleriini of subfamily Galleriinae.
References
Kolar, Heinrich (1942). "Seltsame Geometridenfunde". [Peculiar records of geometer moths]. Zeitschrift des Wiener Entomologen-Vereins. 27: 109. (in German)
Pitkin, Brian & Jenkins, Paul (November 5, 2004). "Nycterosea Hulst, 1896". Butterflies and Moths of the World. Natural History Museum, London. Retrieved May 15, 2019.
Pitkin, Brian & Jenkins, Paul (November 5, 2004). "Percnoptilota Hulst, 1896". Butterflies and Moths of the World. Natural History Museum, London. Retrieved May 15, 2019.
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