Palaeugoa, Durante, 2012

Durante, Antonio, 2012, New genera and problematic species in African Lithosiinae (Lepidoptera, Arctiidae, Lymantriidae), European Journal of Taxonomy 22, pp. 1-16 : 5-11

Palaeugoa gen. nov.

Type species

Xanthetis spurrelli Hampson, 1914 , by present designation.

Diagnosis

Forewings larger than in Xanthetis , as observed after comparison with the type species X. luzonica (Felder, 1875) , with rounded apex. Wing pattern superficially similar to Afrasura , but more punctuate and with different distribution of bands (see differential diagnosis below). Male genitalia resembling Eugoa Walker, 1857 (type species Eugoa aequalis Walker, 1857 from Borneo) with dorsal processes of the tegumen and short and stout uncus, but differing in valvae structure.

Etymology

The name Palaeugoa has no phylogenetic implications, it simply refers to its Western Palaeotropical distribution. The gender is feminine.

Description

The description of Hampson (1914) about the external features is very accurate ( Fig. 3 A-B).

MALE GENITALIA. ( Fig. 3 C-D) With a more robust general structure than in Asura and Afrasura . Uncus short but large; tegumen with conspicuous paratergal sclerites; vinculum slender with a large and shallow saccus; valvae rectangular with straight costa turning inwards at three-quarters. Ala valvae (sacculus) membranous as long as the costal margin, ending in a strong horn-like process. The proximal threequarters of valva surmounted by a distal flap-like formation with a slightly waved margin.

AEDEAGUS. Tubular, slender, slightly curved; vesica with a sparse group of granicula (see Tuxen 1970, for grammatical gender).

FEMALE PHEROMONE GLAND. With a large base and two anterior quite deep lobes.

FEMALE GENITALIA. ( Fig. 3E ) With sinus vaginalis anteriorly delimited by posterior margin of the seventh sternite, forming a slightly sclerotized plica. Posteriorly it is delimited by the scarcely sclerotized eighth sternite, whose anterior margin forms a short backward plica. This is interrupted medially by a funnelshaped excavation that probably serves as a functional ostium bursae and antrum, whereas the true ostium bursae lies deeper at its anterior end, membranous, concealed by the VII sternum plica.

DUCTUS BURSAE. After a very short, narrow and membranous portion, enlarging in a sac-like structure (cervix?) more sclerotized and transversally displaced with scattered spines inside.

CORPUS BURSAE. Spherical, membranous, without signa; ductus seminalis arising caudally from it. Anterior apophyses short, posterior apophyses long and slender. Papillae anales ventrally concealing two small pseudopapillae (sensu Maes 1984).

Remarks

Xanthetis spurrelli from the Gold Coast is a problematic species; it was not placed in the genus Afrasura Durante, 2009 , despite of its similar appearance.

The genus Xanthetis Hampson, 1900 was described based on the type species X. luzonica ( Fig. 4A ) from the Philippines and on X. ichorina (Butler, 1877) ( Fig. 4B ) from Natal, which share a similar wing venation, but differ in wing shape and pattern, and in the genitalic morphology. On the basis of these differences ichorina was transferred to Afrasura by Durante (2009), whereas luzonica is retained in Xanthetis , a genus here considered at least apparently similar to the Australian Asura (the question whether the similarity is due to shared common ancestry is not discussed herein).

The description of spurrelli in Hampson (1914) starts with the statement of the coincidence of veins 3 and 4 in the hindwings, whereas they are stalked in luzonica . It should be remarked once more ( Durante 2004) that this character is inconstant at least among the Lithosiinae , in fact veins 3 and 4 are coincident only in the right hindwing of the examined female of spurrelli from Kumasi, whereas they are stalked in the left hindwing (see also the case of Afrasura ichorina in Durante 2009 ).

The new genus is here proposed due to the instability of the venational characters used by Hampson (loc. cit.) to delineate the taxa, differences in wing pattern and markedly different genitalic morphology.

It could be significant to compare the wings pattern of Palaeugoa gen. nov. to the one of Afrasura .

In their general appearance, the two genera present a quite similar pattern, suggesting a similar response to the selective pressure; however, the substantial differences in the position of the different elements of the pattern and differences in genitalic morphology indicate that they are in fact not closely related.

In fact, Afrasura presents a sequence of band systems that is well defined and shared by all of its species, with the presence of two basal bands considered an apomorphic character ( Durante 2009). The bands correspond as follows:

The different number of bands in the basal and median systems is noteworthy ( Fig. 5 ), and the relative position of the corresponding bands in different areas of the wings is emphasized (i.e. the basal band in Palaeugoa is slightly more basally positioned than the more proximal of the two basal bands in Afrasura , and the two antemedian (AB) bands of the former are more proximally located than the single band (MB) of Afrasura ). A potential inference of this is that the respective positions of wing bands within the symmetry systems of Afrasura and Paleugoa are not homologous.

The second important character complex that should be examined is the genitalic apparatus.

The differences between Asura and Afrasura are both in the general appearance and in the details: the uncus shape of Palaeugoa is never seen in Asura and Afrasura , the tegumen of the former bears two very strong processes (paratergal sclerites), the saccus is very large and shallow, valva with well separated dorsal (supravalva) and ventral (ala valvae) regions ending together in a flap-like structure (perhaps corresponding to the cucullus of Kôda 1987), whereas, in the latter two genera, the paratergal sclerites are only weakly developed, the saccus is deeper and more narrow, valva with the two regions hard to delimit, apart from their two terminal processes. A similar condition is seen in Tumicla , with the exception of the valva, which is even more simple (see Durante 2008).

A more similar genitalia structure is found in the Oriental genus Eugoa (type species Eugoa aequalis (Walker, 1857) , Fig. 6A ). This genus has recently been revised by Holloway (2001) for the Bornean fauna, but some uncertainties still remain; in the present work Eugoa is considered in a very strict sense taking into account only the type species and the very similar Eugoa trilacunata Holloway, 2001 , even if some other species could be included (e.g. Eugoa bipunctata (Walker, 1862)) . Essentially, similarities in the male genitalia of the two genera ( Palaeugoa and Eugoa ) are limited to the short uncus and the well-developed processes of the tegumen, otherwise they are quite different. In Eugoa the uncus itself is of a different shape and surmounted by strong setae (absent in Palaeugoa ); the saccus is practically absent; the valvae represent the most diverging character: they are entire, bearing on the inner margin long costally directed setae, with the sacculus not ending in a distal process ( Fig. 6B ).

Some additional observations are useful in separating the two genera: the forewing shape is rectangularish in Eugoa (quite rounded in Palaeugoa ); in Eugoa the pattern consists of dark fasciae on white-grey ground; forewings venation with Sc anastomosing with R; Rs1 free; the stalked pairs (Rs2+Rs3), (Rs4+M1) and (M2+M3); whereas in Palaeugoa the pattern is as seen in the description above, the anastomosis is lacking, vein Rs2 is absent, all veins are free, but Rs3+Rs4 are stalked.

Taking into account these differences, a close relationship between the two genera is at least doubtful, even though they are referable to the same tribe.

Holloway (2001) did not include Eugoa in any described tribus (according to Bendib & Minet 1999), similarly Palaeugoa is at the moment unassigned.

Palaeugoa spurrelli ( Hampson, 1914) comb. nov. ( Fig. 3 A-E)

Xanthetis spurrelli Hampson, 1914: 728 .

Diagnosis

This species is easily separable from all members of the genus Afrasura on account of its highly distinctive genitalic morphology (uncus, valvae and aedeagus shape). In particular, the composite structure of the valva and its flap-like distal end permit ready distinction from Eugoa aequalis .

Material examined

3 syntypes (1 Ƌ and 2 ♀♀); 1 Ƌ Arct. g.sl. n. 301 BMNH; 1 ♀ Arct. g.sl. n. 5756 BMNH (all in BMNH).

Type locality

GOLD COAST [Ghana], Bibianaha (1 Ƌ, 2 ♀♀ syntypes examined, abdomens not dissected, in BMNH).

Description

See under the generic account.

Distribution

Ghana.

Figures

Fig. 3. Palaeugoa spurrelli (Hampson, 1914). A. Syntype ♀, Ghana, in BMNH. B. ♀, Ghana, in BMNH. C. Ƌ genitalia, g.sl. BM ARCT 301, Ghana. D. Aedeagus, g.sl. BM ARCT 301, Ghana. E. ♀ genitalia, g.sl. BM ARCT 5756, Ghana.

Fig. 4. — A. Xanthetis luzonica (Felder, 1875), holotype Ƌ, Philippines, in BMNH. — B. Afrasura ichorina (Butler, 1877), ♀, South Africa, in BMNH.

Fig. 5. Forewing of Afrasura indecisa (top) and Palaeugoa spurrelli (bottom) and their related pattern symmetry systems. AB, antemedian bands; BB, basal band(s); BD, basal dot; MB, median band; MD, marginal dots; PB, postmedian band(s); SB, submarginal band.

Fig. 6. Eugoa aequalis (Walker, 1857). A. Holotype ♀, Borneo, in BMNH. B. Ƌ genitalia, g.sl. BM ARCT 5057, Borneo. C. Aedeagus, g.sl. BM ARCT 5057, Borneo.