EpinotiaEpinotia brunnichana vs solandriana
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ID: Both species are polymorphic and fasciate forms with a dorsal blotch can be difficult to distinguish. References (MBGBI5.2, BTM and Sterling & Parsons) mention three features that distinguish the two species.
1) the dorsal blotch is triangular in E.solandriana and subquadrate, trapezoid or 4-sided in E.brunnichana.
2) the proximal edge of the dorsal blotch is more oblique in E.solandriana
3) the "apex" of the dorsal blotch is flattened in E.brunnichana
MBGBI5.2 gives:
E.solandriana: dorsal blotch triangular with proximal margin at 45-55° to base and apex sharp
E.brunnichana: dorsal blotch trapezoid with proximal margin at 56-65° to base and apex flattened
In comparing web images labelled as these two species it is apparent that the shape of the dorsal blotch is somewhat variable in both species, and that it may be poorly defined making judgements on the distinction between 'triangular' and 'trapezoid' imprecise. Comparing the drawings of these species available at BTM also gives little support for the stated difference in shape.
It is also not entirely clear from the description in MBGBI5.2 which angle is the "apex" of the dorsal blotch, or what is meant by "base".
If we state that the dorsal blotch is basically triangular such that it has 3 edges (proximal, distal and dorsal) and 3 angles (proximal, distal and medial), we can restate the proposed differences with greater accuracy thus:
E.brunnichana: proximal angle >55°; medial angle truncate; distal angle truncate
E.solandriana: proximal angle <55°; medial angle relatively sharp; distal angle relatively sharp
The proximal edge is straight in both species; the distal edge is usually fairly straight in E.solandriana and may be more curved in E.brunnichana.
It is the truncate medial angle that has given rise to the proposal that the dorsal blotch of E.brunnichana appears more trapezoid; but since the medial angle of E.solandriana is only relatively, rather than absolutely, sharp, its straighter edges and sharper distal angle can give it a trapezoid shape.
These proposed distinctions are illustrated in what I think are unequivocal examples below.
1) the dorsal blotch is triangular in E.solandriana and subquadrate, trapezoid or 4-sided in E.brunnichana.
2) the proximal edge of the dorsal blotch is more oblique in E.solandriana
3) the "apex" of the dorsal blotch is flattened in E.brunnichana
MBGBI5.2 gives:
E.solandriana: dorsal blotch triangular with proximal margin at 45-55° to base and apex sharp
E.brunnichana: dorsal blotch trapezoid with proximal margin at 56-65° to base and apex flattened
In comparing web images labelled as these two species it is apparent that the shape of the dorsal blotch is somewhat variable in both species, and that it may be poorly defined making judgements on the distinction between 'triangular' and 'trapezoid' imprecise. Comparing the drawings of these species available at BTM also gives little support for the stated difference in shape.
It is also not entirely clear from the description in MBGBI5.2 which angle is the "apex" of the dorsal blotch, or what is meant by "base".
If we state that the dorsal blotch is basically triangular such that it has 3 edges (proximal, distal and dorsal) and 3 angles (proximal, distal and medial), we can restate the proposed differences with greater accuracy thus:
E.brunnichana: proximal angle >55°; medial angle truncate; distal angle truncate
E.solandriana: proximal angle <55°; medial angle relatively sharp; distal angle relatively sharp
The proximal edge is straight in both species; the distal edge is usually fairly straight in E.solandriana and may be more curved in E.brunnichana.
It is the truncate medial angle that has given rise to the proposal that the dorsal blotch of E.brunnichana appears more trapezoid; but since the medial angle of E.solandriana is only relatively, rather than absolutely, sharp, its straighter edges and sharper distal angle can give it a trapezoid shape.
These proposed distinctions are illustrated in what I think are unequivocal examples below.
Having established that in the MBGBI5.2 distinctions mentioned above the "base" is the dorsal edge and the "apex" is the medial angle, it remains unclear whether the measurement of the proximal angle were made on a live moth viewed in profile or on a detached flattened wing. For the two specimens presented above the measurements made from images of the live moths are 61° and 45° respectively. This combined with a look at the "problem" at the end of this page are sufficient for me to conclude that measurement of the proximal angle is an unreliable means of distinguishing the species.
Male genitalia: The main difference between the species, as illustrated at Moth Dissection, is in the extent of the cucullus distal to a row of spines on its anteroventral margin, which relatively long in E.brunnichana. In the illustration below a line is drawn from the proximal end of the cucullar spine patch to the apex of the cucullus and a second line is drawn from the distal end of the cucullar spine patch to meet the first line at 90°. In these examples the proportion of the cucullus with marginal spines (spine ratio) is 0.54 for E.brunnichana and 0.68 for E.solandriana.
Having re-examined all my images the specimen presented here is the only definite male E.brunnichana and the range of values of the spine ratio for 5 E.solandriana specimens is 0.64 - 0.70.
The concavity between sacculus and cucullus is deeper in E.solandriana (outlined in fig) and possibly (personal observation) the marginal spines may project into the cucullar end of the concavity in E.solandriana, but not in E.brunnichana (arrowed in fig).
Having re-examined all my images the specimen presented here is the only definite male E.brunnichana and the range of values of the spine ratio for 5 E.solandriana specimens is 0.64 - 0.70.
The concavity between sacculus and cucullus is deeper in E.solandriana (outlined in fig) and possibly (personal observation) the marginal spines may project into the cucullar end of the concavity in E.solandriana, but not in E.brunnichana (arrowed in fig).
Female genitalia: Illustrated in MBGBI5.2 (fig 253) and shown at Moth Dissection, the latter with some description of the distinction between the species. Features for E.solandriana given first: 1) Sterigma wider and flat-"topped" vs narrower and usually notched; 2) Signa in anterior half (cranial, bottom in usual presentation) of the corpus bursae and orientated more-or-less transversely vs one signum in posterior half, one in anterior half and both orientated at 45°.
Both of these distinctions are to some extent problematic:
1) The sterigma (ostial plate) has connected posterodorsal (lamella postvaginalis) and anteroventral (lamella antevaginalis) components; it is the posterior margin of the posterodorsal component that is supposed to be flat vs notched. The apparent width will vary with degree of compression and the posterior margin is somewhat irregular in both species, so that a clear distinction on this feature can only be made with confidence when the plate is distinctly notched (assuming this is a valid feature). I have observed in my own material (assuming they are correctly identified) that the lamella antevaginalis is noticeably deeper in E.solandriana - but this feature is not clearly demonstrated by all the images labelled as E.solandriana at Moth Dissection.
2) There is a potential confusion in the determination of "transverse" in specimens where the ductus bursae is kinked such that the long axis of the corpus bursae is not in the long axis of the abdomen - I believe it is the long axis of the corpus bursae that is relevant here - but it this is not always easy to determine.
Problem: