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Choristoneura diversana
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Choristoneura hebenstreitella
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The two extant Choristoneura species are fairly easily distinguishable from each other of external features (see table); but are more difficult to distinguish from some other Archipini.
Web images labelled as C.diversana seem quite variable and it is probably overlooked amongst the more abundant Pandemis species. I would think genital determination would be required to confidently identify this species. C.hebenstreitella will usually be distinguishable from Pandemis species by the broken median fascia and the diffuse distal margin to the dorsal component of this fascia.
C.diversana |
C.hebenstreitella |
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size |
ws: ♂15-20, ♀19-23 fw: ♂7-9.5, ♀9-10.5 |
ws: ♂19-25, ♀24-30; fw: ♂9-12, ♀11-15 |
ground colour |
yellow-brown |
brown |
distal margin of subbasal fascia |
curved (convex distally) |
fairly straight |
Male genitalia
Choristoneura species are readily distinguished from Pandemis by the shape of the uncus - elongate in Choritoneura, ~quadrate in Pandemis
Choristoneura diversana
Uncus broadest near middle, apex truncate. Valva reduce. Aedeagus slightly twisted on its long axis; dorsal surface obtusely angled; apex rounded with a subapical dorsal projection.
Uncus broadest near middle, apex truncate. Valva reduce. Aedeagus slightly twisted on its long axis; dorsal surface obtusely angled; apex rounded with a subapical dorsal projection.
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Choristoneura hebenstreitella
Uncus ~parallel-sided, apex rounded and flattened. Valva full. Aedeagus smoothly curved; apex squarely truncate with an apical dorsal projection.
Uncus ~parallel-sided, apex rounded and flattened. Valva full. Aedeagus smoothly curved; apex squarely truncate with an apical dorsal projection.
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Choristoneura lafauryana (Extinct in Britain)
Uncus broadening slightly from base to apex, apex rounded and flattened. Valva full. The sacculus as a long curved spur projecting from its anteroventral margin at ~⅖ from the base and the apical ⅗ is a narrow spur along the valval margin. (This seems sufficiently variant from the other Choristoneura species to question its placement in this genus).
Uncus broadening slightly from base to apex, apex rounded and flattened. Valva full. The sacculus as a long curved spur projecting from its anteroventral margin at ~⅖ from the base and the apical ⅗ is a narrow spur along the valval margin. (This seems sufficiently variant from the other Choristoneura species to question its placement in this genus).
Female genitalia
Choristoneura species are readily distinguished from Pandemis by the sclerotised line extending the whole length of the long, narrow, coiled ductus bursae (no sclerotised line, broader and ~straight in Pandemis). The two Choristoneura species are separated on the form of the signum; in both species this consists of a narrow spike with an extension at its base. In C.diversana the extension is slightly more than ½ the length of the spike; in C.hebenstreitella the extension much shorter.
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All images © Chris Lewis
Page published 23/01/2021
