Kessleria dimorpha , Huemer, Peter & Mutanen, Marko, 2015

Huemer, Peter & Mutanen, Marko, 2015, Alpha taxonomy of the genus Kessleria Nowicki, 1864, revisited in light of DNA-barcoding (Lepidoptera, Yponomeutidae), ZooKeys 503, pp. 89-133: 89

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scientific name

Kessleria dimorpha

sp. n.

Taxon classification Animalia Lepidoptera Yponomeutidae

Kessleria dimorpha  sp. n.

Type material.

Holotype. ♂, "Frankreich Dep. Hautes-Alpes Col Agnel, 2770 m 6°59'02"E, 44°41'10"N 4.8.2010, leg. Huemer TLMF 2011-010" "BC TLMF Lep 01756" "YPO 158 ♂ P. Huemer" (TLMF).

Paratypes. France: 7 ♂, 5 ♀, same data, genitalia slides YPO 149 ♂ P. Huemer, YPO 159 ♀ P. Huemer, DNA barcode IDs TLMF Lep 01757, TLMF Lep 01758, TLMF Lep 01759 (TLMF); 4 ♂, 1 ♀, same data, leg. Wieser (LMK).


Kessleria dimorpha  resembles other taxa of the Kessleria alternans  -group in wing markings and colour (Figs 2-11), but the male differs from the genetically nearest neighbour Kessleria cottiensis  by the on average distinctly larger forewing length of 8.25 mm (n=6) vs. 7.59 mm (n=14). Larger species are Kessleria wehrlii  with forewing length 8.75 mm (n=13) and Kessleria alternans  with 8.55 mm (n=26), whereas Kessleria alpmaritimae  with 8.05 mm (n=6) is of similar size. Furthermore, Kessleria wehrlii  and Kessleria alpmaritimae  have a much more prominent whitish suffusion on the forewing, whereas the ochre-brown markings of Kessleria dimorpha  rather resemble Kessleria alternans  . The female of Kessleria dimorpha  reflects a tendency to reinforced brachyptery and is distinctly smaller than Kessleria alternans  with a forewing length of only 6.0 mm (n=4) on average vs. 7.58 mm (n=11), whereas females of Kessleria cottiensis  and Kessleria alpmaritimae  are strongly suffused with whitish scales. Kessleria wehrlii  is insufficiently known from only a single worn female specimen. The male genitalia differ from all other taxa of the Kessleria alternans  -group by the distinctly shorter phallus with <1.40 mm vs. a minimum of 1.50 mm in other species (Figs 12-21). The female genitalia show no diagnostic characters to related species of the Kessleria alternans  -group (Figs 22-31).


Male (Fig. 6). Head covered with ochre-brown hair-like scales; antennae almost unicolorous dark grey-brown; thorax and tegulae mixed dark grey-brown and ochre-brown. Forewing length 8.0-8.4 mm ( Ø 8.25 mm; n=6); ground colour dark grey, intensively mottled with light grey, ochre-brown and whitish scales, white medial patch in fold; black dots particularly on costal and subcostal veins; black patch near base and at end of cell, oblique blackish fascia at about 1/3 to 1/2 reduced to large patch in fold; termen mixed dark and light grey; fringes basally dark grey, distal part whitish-grey, darker in apical area. Hindwing dark grey, fringes with dark grey base, distal part whitish-grey.

Female (Fig. 7). Head covered with erected whitish hair-like scales; antennae grey-brown, indistinctly lighter ringed; thorax and tegulae whitish. Forewing length 6.0 mm ( Ø 6.0 mm; n=4); ground colour whitish, mottled with dark grey and black, particularly along fold and in tornal part, few black dots along costal and subcostal vein, small patches of ochre-brown scales in medial part of wing particularly in fold and at end of cell; oblique blackish fascia at about 1/3 to 1/2 indistinct, separated into larger dash-like patch and reduced dot; termen mixed whitish and dark grey; fringes whitish-grey, with dark grey basal part near apex. Hindwing grey, fringes whitish-grey with darker basal part.

Male genitalia (Figs 16-17). Socii long and slender, with apical spine; anterior margin of tegumen with medial process; gnathos broadly tongue-shaped, smooth; valva moderately slender, length 0.71-0.72 mm, medially weakly widened, maximum width of about 0.26-0.28 mm, densely covered with long hairs in medial part and short setae on ventromedial margin, ventromedial part weakly convex, distal part moderately slender with ventrally convex and dorsally projected apex, costa strongly sclerotized with weak distal dentation; sacculus oval, weakly confined, densely covered with strong setae; saccus short, about 0.32 mm, stout, about same width throughout, apex rounded; phallus ca. 1.32-1.36 mm long and slender, straight, apically with distinct reticulate sculpture, uneverted vesica with ca. 0.58-0.60 mm long sclerotized part, three to four prominent needle-shaped cornuti of about 0.38-0.40 mm in length.

Female genitalia (Figs 24, 29). Genitalia ca. 4.9 mm in length; papilla analis large, densely covered with long setae; apophysis posterior rod like, ca. 0.72 mm, about length of apophysis anterior; apophysis anterior rod like; posterior part bifurcated with straight dorsal and inwardly curved ventral branch; lamella postvaginalis with large sclerotized mediolateral patches, covered with microtrichia, medial area less sclerotize, posterolateral part with hump, covered with some long setae; ostium bursae membranous; antrum weakly sclerotized, funnel-shaped; ductus bursae long, ca. 2.3 mm, posterior part from entrance of ductus seminalis anterior and anterior part covered with finely granulous sculpture, medial part with weak and hardly discernible sculpture, ductus bursae extended into posterior part of corpus bursae, entrance to corpus bursae weakly widened; corpus bursae well delimited, about 1.4 mm in length, ovoid, with small plate-like signum.

Molecular data.

The average intraspecific divergence of the barcode region is low with 0.08%, ranging from a minimum of 0% to a maximum of 0.15% (n=4). The minimum distance to the nearest neighbour Kessleria cottiensis  is 1.86%, whereas the minimum divergence to Kessleria alternans  , Kessleria alpmaritimae  and Kessleria wehrlii  ranges from 3.15% and 3.64% to 4.3%, respectively.


The species name refers to the remarkable sexual dimorphism.


(Fig. 32). Only known from the type locality, the French side of Col Agnel (Cottian Alps), close to the Italian border.


Host-plant and early stages unknown. Based on the type locality, the host-plant is most likely Saxifraga cf. oppositifolia  . The adults have been collected in early August during the early morning hours from about 7-10a.m. at low temperatures between 2-5 °C. Males were flying actively during this period in search for females. Both sexes were later found in copula, often sitting on cushions of their suspected host-plant. A single female was found at light, attracted from its nearby habitat and crawling upwards to the light tower, but unable to fly actively. From personal observations of PH, it is likely that the slightly reinforced brachyptery of Kessleria dimorpha  is combined with flightlessness. The species occurs in rocky habitat on siliceous soil. Vertical distribution: about 2800 m.


Fringes of the examined females seem partially lost and thus may lead to a biased impression of the extent of wing reduction.