Insects of Britain and Ireland: the genera of grass moths (Pyralidae-Crambinae and Schoenobiinae)

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L. Watson and M. J. Dallwitz

Pediasia Hübner

Adults. Face without a conical hairy prominence. Proboscis functional.

Wingspan 18–26 mm. The adults conspicuously sexually dimorphic, or not very sexually dimorphic. Forewings pale whitish-ochreous with paler veins, with ill-defined dark streaks interneurally between the cell and the dorsum, with the cilia chequered white and brown (P. fascelinella, the markings darker in males); or dull greyish- to dark ferrugineous-ochreous and extensively irrorated fuscous with only faint markings, the fringe dark grey except for the narrowly pale base (P. contaminella, with occasional melanics); or ochreous, rather paler on the veins, with a conspicuous blackish streak from the base to about half-way and a short crescentic blackish mark towards the middle of this between it and the dorsum, and slightly glossy including the concolorous grey fringe. The fringe not glistening-metallic. The fringe conspicuously chequered, or not chequered. Forewing apices rounded, or pointed (in P. contaminella and P. aridella); termen sinuate, or non-sinuate (convex, in P. fascelinella). Ground colour of the forewings whitish, or ochreous, or dark fuscous. Forewings plain (P. contaminella), or conspicuously patterned with contrasting colours. The patterning when manifest, complex; comprising both longitudinal streaking and transverse markings (the angled median and subterminal lines well defined or faint). Forewings with a median line; usually transversely dark-lined towards the termen; the subterminal lines not white-edged; without a strong white median streak; without conspicuous white marks at or near the apex; without a scattering of large black scales. Forewing vein 7 arising from vein 8. Hindwings whitish, or pale fuscous, or pale grey, or dark fuscous; plain, or with a subterminal dark line (posteriorly, in P. aridella); very pale brownish whitish, tending somewhat darker terminally and apically, the fringe white (P. fascelinella), whitish basally to pale grey and tending darker postmedianly, with a slightly paler fringe (P. contaminella); or whitish basally to pale grey tending darker postmedianly and with a faint subterminal dark line terminating in a dark tornal spot, the fringe white (P. aridella).

Distribution and habitats. England. Occurring in coastal locations and inland. In wet places, mesophytic habitats, and dry places. British species: P. aridella, P. contaminella, P. fascelinella. Adults abroad June to August, or September.

Larvae. Larvae feeding on monocots; Poaceae (inhabiting silken tubes in or around the culm bases of grasses: Ammophila (P. fascelinella), Festuca ovina etc. (P. contaminella), Puccinellia maritima (P. aridella)). Inhabiting coastal sandhills (P. fascelinella), dry grasslands (P. contaminella) and the margins of saltmarshes (P. aridella).

Subfamily. Crambinae.

Illustrations. • Pediasia contaminella and P. fascelinella, with species of Agriphila, Catoptria, Chrysocrambus, Crambus and Thisanotia: Leech, 1886. • Pediasia aridella, P. contaminella and P. fascelinella: Barrett. • P. aridella and P. contaminella: forewing patterns. • Hübner's illustrations (1796–1813) of 4 Pediasia species (1796–1813).

To view the illustrations with detailed captions, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2003 onwards. Insects of Britain and Ireland: the genera of grass moths (Pyralidae-Crambinae and Schoenobiinae). Version: 8th June 2016.’.