|
173 Oligia strigilis (Marbled Minor)
|
174 Oligia latruncula (Tawny Marbled Minor)
|
175 Oligia versicolor (Rufous Minor)
|
|
176 Oligia fasciuncula (Middle-barred Minor)
|
The Oligia species are all very variable. They commonly have antemedian and postmedian lines which allows separation from Litoligia literosa (Rosy Minor) which has antemedian and median lines – so that the kidney mark is placed within a broad, though often indistinct, median fascia in the Oligia species, but distal to a narrow median fascia in L.literosa. Oligia species also commonly have a black paradorsal bar connecting the cross-lines and the area between postmedian and subterminal lines is often whitish.
O.fasciuncula can usually be identified on external features, but the other three species require genital dissection for reliable identification.
Possibly helpful trends are mentioned by Waring & Townsend: larger specimens with a chalky white subterminal band and an orange posterior thoracic tuft are likely to be O.strigilis; well-marked specimens with pale brown oval and kidney marks are likely to be O.versicolor; blackish specimens with a brown median or subterminal fascia and no orange posterior thoracic tuft are likely to be O.latruncula.
Genital differences are covered by the Difficult Species Guide, both sexes of all four species are shown at Moth Dissection and all except O.fasciuncula are illustrated in MBGBI10 pp207,208
O.fasciuncula can usually be identified on external features, but the other three species require genital dissection for reliable identification.
Possibly helpful trends are mentioned by Waring & Townsend: larger specimens with a chalky white subterminal band and an orange posterior thoracic tuft are likely to be O.strigilis; well-marked specimens with pale brown oval and kidney marks are likely to be O.versicolor; blackish specimens with a brown median or subterminal fascia and no orange posterior thoracic tuft are likely to be O.latruncula.
Genital differences are covered by the Difficult Species Guide, both sexes of all four species are shown at Moth Dissection and all except O.fasciuncula are illustrated in MBGBI10 pp207,208
Male genitalia: Consistent and reliable differences occur in the structure of the harpe, pollex and clavus.
Harpe: O.strigilis - long, slender and almost straight; O.latruncula - short, broad, flattened and triangular; O.versicolor - long (but shorter and stouter than in O.strigilis) and distinctly curved; O.fasciuncula - long, slender and almost straight.
Pollex: this ventral extension of the cucullus is a characteristic of the genus. In O.latruncula it is relatively short and stout; in the other 3 species it is long and slender.
Relative length of harpe and pollex: (there is difficulty in determining exactly where the base of each structure should be measured from)
O.strigilis - ~ equal; O.latruncula - harpe slightly longer; O.versicolor - harpe slightly shorter; O.fasciuncula - harpe much longer.
Clavus: heavily sclerotised and setose in all four species. Possibly of greatest utility in aiding the distinction between O.strigilis and O.versicolor. DSG states that it is "relatively short" in O.strigilis and "more elongated" in O.versicolor - however, in my experience and in comparison of web images and the illustrations in MBGBI10, I think it is more true to say that it is more acutely tapered towards the apex in O.versicolor and more bulbed at the base in O.strigilis - the actual length seems quite variable in both species. it also seems to be significantly more densely setose in O.strigilis.
Harpe: O.strigilis - long, slender and almost straight; O.latruncula - short, broad, flattened and triangular; O.versicolor - long (but shorter and stouter than in O.strigilis) and distinctly curved; O.fasciuncula - long, slender and almost straight.
Pollex: this ventral extension of the cucullus is a characteristic of the genus. In O.latruncula it is relatively short and stout; in the other 3 species it is long and slender.
Relative length of harpe and pollex: (there is difficulty in determining exactly where the base of each structure should be measured from)
O.strigilis - ~ equal; O.latruncula - harpe slightly longer; O.versicolor - harpe slightly shorter; O.fasciuncula - harpe much longer.
Clavus: heavily sclerotised and setose in all four species. Possibly of greatest utility in aiding the distinction between O.strigilis and O.versicolor. DSG states that it is "relatively short" in O.strigilis and "more elongated" in O.versicolor - however, in my experience and in comparison of web images and the illustrations in MBGBI10, I think it is more true to say that it is more acutely tapered towards the apex in O.versicolor and more bulbed at the base in O.strigilis - the actual length seems quite variable in both species. it also seems to be significantly more densely setose in O.strigilis.
O.strigilis (Marbled Minor)
|
O.latruncula (Tawny Marbled Minor)
|
O.versicolor (Rufous Minor)
|
O.fasciuncula (Middle-barred Minor)
|
Female genitalia
In both O.strigilis and O.fasciuncula there is a distinct constriction between the antrum and ductus bursae; O.strigilis has a distinct sclerotised area in the corpus bursae which is lacking in the image of the female genitalia of O.fasciuncula at Moth Dissection.
In both O.latruncula and O.versicolor there is not a distinct constriction between antrum and ductus bursae; O.versicolor has a large sclerotised area in the corpus bursae while O.latruncula has a small sclerotised area.
In both O.strigilis and O.fasciuncula there is a distinct constriction between the antrum and ductus bursae; O.strigilis has a distinct sclerotised area in the corpus bursae which is lacking in the image of the female genitalia of O.fasciuncula at Moth Dissection.
In both O.latruncula and O.versicolor there is not a distinct constriction between antrum and ductus bursae; O.versicolor has a large sclerotised area in the corpus bursae while O.latruncula has a small sclerotised area.
O.strigilis (Marbled Minor)
|
O.latruncula (Tawny Marbled Minor)
|
Page published 16/04/2016
