Identification of Hoplodrina species
H.octogenaria (Uncertain)
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H.blanda (Rustic)
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H.superstes (Powdered Rustic) |
H.ambigua (Vine's Rustic)
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Biology
Status & distribution: H.octogenaria and H.blanda are common in England & Wales, local in Scotland. H.ambigua is common in England and South Wales. H.superstes is a very rare migrant.
Flight season: H.octogenaria and H.blanda fly June to August with a partial second generation in October. H.ambigua is bivoltine May-July, August to September.
Size: All are similarly sized with forewing lengths in the range 13-16mm, but H.octogenaria (fw: 14-16mm [W&T] 14.2-15.9 [BL]) averages larger than H.blanda (13-16mm [W&T] 13.0-14.8 [BL]) which averages larger than H.ambigua (13-15mm [W&T] 11.6-13.0 [BL])
Status & distribution: H.octogenaria and H.blanda are common in England & Wales, local in Scotland. H.ambigua is common in England and South Wales. H.superstes is a very rare migrant.
Flight season: H.octogenaria and H.blanda fly June to August with a partial second generation in October. H.ambigua is bivoltine May-July, August to September.
Size: All are similarly sized with forewing lengths in the range 13-16mm, but H.octogenaria (fw: 14-16mm [W&T] 14.2-15.9 [BL]) averages larger than H.blanda (13-16mm [W&T] 13.0-14.8 [BL]) which averages larger than H.ambigua (13-15mm [W&T] 11.6-13.0 [BL])
Forewing
Colour: H.octogenaria - various shades of brown. H.blanda - various shades of brown or grey or blackish. H.superstes - pale brown with brown speckling. H.ambigua - various shades of brownish-grey or silvery-grey.
Stigmata: H.octogenaria and H.blanda have a small round oval and a kidney-shaped kidney mark. H.superstes and H.ambigua have a larger round oval and a rounder kidney mark. This means that if we ignore the possibility of H.superstes, H.ambigua can usually be identified as distinct from H.octogenaria/H.blanda by its larger oval mark and most of the identification problem is in distinguishing H.octogenaria from H.blanda.
Caradrina morpheus (Mottled Rustic) is also similar but has blurred stigmata without pale edging.
Colour: H.octogenaria - various shades of brown. H.blanda - various shades of brown or grey or blackish. H.superstes - pale brown with brown speckling. H.ambigua - various shades of brownish-grey or silvery-grey.
Stigmata: H.octogenaria and H.blanda have a small round oval and a kidney-shaped kidney mark. H.superstes and H.ambigua have a larger round oval and a rounder kidney mark. This means that if we ignore the possibility of H.superstes, H.ambigua can usually be identified as distinct from H.octogenaria/H.blanda by its larger oval mark and most of the identification problem is in distinguishing H.octogenaria from H.blanda.
Caradrina morpheus (Mottled Rustic) is also similar but has blurred stigmata without pale edging.
H.octogenaria vs H.blanda:
Both have blackish basal, antemedian and postmedian lines, and stigmata darker than the ground colour, usually pale-outlined
In H.octogenaria the postmedian line is scalloped with dots at each vein crossing; in H.blanda only the neural dots are present.
In H.octogenaria a narrow diffuse median fascia extends from the dorsum to the kidney mark; this fascia is either absent or indistinct in H.blanda.
Some specimens have characters of both species and genital examination may be required to determine the species
Both have blackish basal, antemedian and postmedian lines, and stigmata darker than the ground colour, usually pale-outlined
In H.octogenaria the postmedian line is scalloped with dots at each vein crossing; in H.blanda only the neural dots are present.
In H.octogenaria a narrow diffuse median fascia extends from the dorsum to the kidney mark; this fascia is either absent or indistinct in H.blanda.
Some specimens have characters of both species and genital examination may be required to determine the species
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Hindwing:
In H.octogenaria and H.blanda the hindwing is brownish-grey in the male, grey in the female. In H.ambigua it is whitish in both sexes.
In H.octogenaria and H.blanda the hindwing is brownish-grey in the male, grey in the female. In H.ambigua it is whitish in both sexes.
Antenna:
Male H.ambigua has fasciculate antennae with cilia as long as the width of the antennal shaft. Male H.superstes also has fasciculate antennae, but with short cilia. Male H.octogenaria and H.blanda and females of all four species have simple antennae.
Male H.ambigua has fasciculate antennae with cilia as long as the width of the antennal shaft. Male H.superstes also has fasciculate antennae, but with short cilia. Male H.octogenaria and H.blanda and females of all four species have simple antennae.
Male genitalia:
Refs: MBGBI10, Moth Dissection, Difficult Species Guide.
1) Cornuti. All 4 species have a large cluster of medium cornuti in the basal 2/3 of the aedeagus and a separate group of cornuti in the apical 1/3. H.ambigua is distinct in having the cornuti in the apical group with 4-6 cornuti significantly larger than those in the basal group (these can be identified without opening or everting the aedeagus)*. In the other 3 species the apical cornuti are in two groups arranged on a diverticulum.*
The critical feature is the number and position of cornuti in the smaller of the two groups on the diverticulum: 5-9 cornuti on the side of the diverticulum in H.octognaria, 12-20 near the apex of the diverticulum in H.blanda. The arrangement in H.superstes appears similar to H.octogenaria and these two are probably best distinguished on external features.**
* Referring to H.ambigua, DSG states: "everted vesica shows several very large pointed cornuti in basal half". This apparent confusion arises because cornuti which were nearest the apex of the aedeagus become the most basal cornuti when the vesica is everted. The diverticulum on which the apical groups of cornuti are arranged is referred to as the "first diverticulum" by DSG when referring to H.octogenaria and as the "basal diverticulum" by Moth Dissection and by DSG when referring to H.blanda.
**According to DSG the critical feature is the length of the diverticulum: "elongate" in H.blanda, "small" in H.octogenaria.
Refs: MBGBI10, Moth Dissection, Difficult Species Guide.
1) Cornuti. All 4 species have a large cluster of medium cornuti in the basal 2/3 of the aedeagus and a separate group of cornuti in the apical 1/3. H.ambigua is distinct in having the cornuti in the apical group with 4-6 cornuti significantly larger than those in the basal group (these can be identified without opening or everting the aedeagus)*. In the other 3 species the apical cornuti are in two groups arranged on a diverticulum.*
The critical feature is the number and position of cornuti in the smaller of the two groups on the diverticulum: 5-9 cornuti on the side of the diverticulum in H.octognaria, 12-20 near the apex of the diverticulum in H.blanda. The arrangement in H.superstes appears similar to H.octogenaria and these two are probably best distinguished on external features.**
* Referring to H.ambigua, DSG states: "everted vesica shows several very large pointed cornuti in basal half". This apparent confusion arises because cornuti which were nearest the apex of the aedeagus become the most basal cornuti when the vesica is everted. The diverticulum on which the apical groups of cornuti are arranged is referred to as the "first diverticulum" by DSG when referring to H.octogenaria and as the "basal diverticulum" by Moth Dissection and by DSG when referring to H.blanda.
**According to DSG the critical feature is the length of the diverticulum: "elongate" in H.blanda, "small" in H.octogenaria.
2) Juxta
The shape of the juxta may also help to distinguish H.blanda/octogenaria: in both it is elongate triangular with concave lateral margins; in H.blanda it narrows gradually from the base to a pointed apex; in H.octogenaria it narrows from the base but the apical half is of fairly even width and the apex truncate.*
* DSG refers to the juxta as being "conical" in H.blanda and "trumpet-shaped" in H.octogenaria; and comments that "the shape of the juxta can be hard to discern or misleading if this area is not cleaned correctly ... or if it is not laid completely flat.." I don't think the description "trumpet-shaped" is necessarily distinct from "conical" and being a 3-dimensional shape, there is no such thing as a flat cone - so this will always be impossible to discern!
The shape of the juxta may also help to distinguish H.blanda/octogenaria: in both it is elongate triangular with concave lateral margins; in H.blanda it narrows gradually from the base to a pointed apex; in H.octogenaria it narrows from the base but the apical half is of fairly even width and the apex truncate.*
* DSG refers to the juxta as being "conical" in H.blanda and "trumpet-shaped" in H.octogenaria; and comments that "the shape of the juxta can be hard to discern or misleading if this area is not cleaned correctly ... or if it is not laid completely flat.." I don't think the description "trumpet-shaped" is necessarily distinct from "conical" and being a 3-dimensional shape, there is no such thing as a flat cone - so this will always be impossible to discern!
3) Valva
The distal end of the sacculus is bluntly produced in H.ambigua, flush with the rest of the internal lamina in the other 3 species. H.ambigua may be further distinguishable by having a broader more strongly curved mid-valval process than in the other 3 species.
The distal end of the sacculus is bluntly produced in H.ambigua, flush with the rest of the internal lamina in the other 3 species. H.ambigua may be further distinguishable by having a broader more strongly curved mid-valval process than in the other 3 species.
Female genitalia:
Refs: MBGBI10, Moth Dissection, Difficult Species Guide.
In all 4 species the posterior half of the corpus bursae bulges to the left and right of the ductus bursae, the left bulge giving origin to the ductus seminilis. H.ambigua lacks any substantial sclerotisation of the posterior pole of either bulge and in has a noticeably larger right bulge than is seen in the other 3 species.* H.superstes has the posterior poles of both bulges well-sclerotised. H.octogenaria and H.blanda have only the left bulge sclerotised. According to DSG, in H.octogenaria the ostium is broader and the ductus bursae shorter and broader than in H.blanda. - but this distinction is not readily perceivable by comparing images at Moth Dissection.
*DSG distinguishes H.ambigua as having the corpus bursae divided into 2 lobes, which it isn't, and doesn't mention the obvious difference in sclerotisation. It also mentions as a key feature that the ductus bursae of H.ambigua is strongly sclerotised - but it doesn't seem to be any more well-sclerotised than in the other 3 species.
Refs: MBGBI10, Moth Dissection, Difficult Species Guide.
In all 4 species the posterior half of the corpus bursae bulges to the left and right of the ductus bursae, the left bulge giving origin to the ductus seminilis. H.ambigua lacks any substantial sclerotisation of the posterior pole of either bulge and in has a noticeably larger right bulge than is seen in the other 3 species.* H.superstes has the posterior poles of both bulges well-sclerotised. H.octogenaria and H.blanda have only the left bulge sclerotised. According to DSG, in H.octogenaria the ostium is broader and the ductus bursae shorter and broader than in H.blanda. - but this distinction is not readily perceivable by comparing images at Moth Dissection.
*DSG distinguishes H.ambigua as having the corpus bursae divided into 2 lobes, which it isn't, and doesn't mention the obvious difference in sclerotisation. It also mentions as a key feature that the ductus bursae of H.ambigua is strongly sclerotised - but it doesn't seem to be any more well-sclerotised than in the other 3 species.
Images to follow when fresh material obtained
Page published 06/12/2024
