| 1 | Frons and vertex bright yellow, thorax purplish black |
| | 12.0-14.0mm. May and June. Forewing unicolorous purplish black except plical and second stigmata which are black with raised scales. Labial palpus black and yellow. |
| - | Frons and vertex concolorous with thorax |
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| 2 (1) | Forewing predominantly orange or yellow |
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| - | Forewing predominantly dark brown |
| | Paler areas of forewing sometimes partly suffused with ochreous yellow scales. |
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| 3 (2) | Forewing yellow, whitish towards base. Vertex, frons and labial palpus shining white; antenna pale grey, indistinctly annulated darker |
| | 14.0-18.0mm. July (in Central Europe also in August). Forewing with dark brown costal streak and two large brown spots, at two-fifth and at tornus respectively. |
| - | Forewing bright orange. Vertex, frons and labial palpus brassy blackish brown; antenna blackish brown, white apically |
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| 4 (3) | Forewing bordered dark brown, with streak along costa comparatively narrow, not connected with dark brown dorsal streak |
| | 10.0-13.0mm. Late June to early August. Forewing with three larger and two smaller tubercular silvery spots. |
| - | Forewing bordered dark brown, with streak along costa comparatively broad and connected with brown dorsal streak at one-third, forming a broad dark brown fascia. |
| | 11.0-13.0mm. July (June to August in Great Britain). Forewing with pattern of silvery spots similar to that of the preceding species. |
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| 5 (2) | Frons and vertex shining dark greyish brown |
| | 9.0-12.0mm. Early June to early August (abroad). Forewing with whitish markings reduced, pale costal spot at three quarters rather distinct. |
| - | Frons and vertex white or whitish, more or less suffused with dark brown |
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| 6 (5) | Forewing with pale colour creamy, pale dorsal streak at least in basal area partly suffused with ochreous yellow |
| | 11.0-12.5mm. Early June to mid August. Melanistic forms occur. |
| - | Forewing with pale colour pure white, without ochreous yellow suffusion |
| | 10.0-11.5mm. Late May to early July. |
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