Hemithea squalidaria O. G. Costa, 1848, combination and status uncertain

squalidaria O. G. Costa, 1848, Fauna Regno Napoli (Ent.): [331], pl. (Geom.) 2, fig. 4, ( Hemithea). Syntype (s), [Italy]: Adriatic coast: San Cataldo, near Lecce; Tyrrhenian coast: [Lago di] Patria [near Naples].

Hemithea squalidaria O. G. Costa, 1848 from southern Italy (Figure 5a) is a problematic taxon due to the lack of type material. Only the original, hand-drawn colour illustration on the taxon exists (reprinted in Figure 5a). Prout (1912 –1916) combined squalidaria with Ellopia Stephens (= Hylaea), due to its similarity with H. compararia (Staudinger, 1894) . Wehrli (1939 –1954), in the absence of material, treated squalidaria putatively valid at species level, as did Scoble (1999).

If Hemithea squalidaria belonged to the genus Hylaea, in theory it could be conspecific with H. mediterranea . Hemithea squalidaria has rather straight and well developed forewing medial lines, and the hindwing postmedial line is clearly curved (Figure 5a), whereas the forewing antemedial line is curved towards the costa and the hindwing postmedial line is only slightly curved in H. mediterranea (Figures 2, 7). Costa (1848) gives squalidaria ’s wingspan as 13 linee, which is 2.33 cm, assuming he used the old Sicilian definition of line, one line being equal to 1/12 of an Sicilian ounce. Costa also reported the same wingspan for Thetidia smaragdaria (Fabricius, 1787), which is generally smaller than Hylaea specimens. Further, the specimen has simple (fasciculate?) antennas and long labial palpi, thus different from Hylaea (males). Therefore, in our opinion, the original hand-drawn illustration of H. squalidaria and the description of the taxon reported in Costa's text (e.g. the wingspan of ca. 23 mm) exclude the possibility of Hemithea squalidaria being conspecific with H. mediterranea (smallest H. mediterranea male available to us has a wingspan of 31 mm, smallest female is 37 mm). Hylaea compararia and H. fasciaria are externally different and, according to the current knowledge, they do not occur in southern Italy.

Based on the illustration (reprinted in Figure 5a), we are unable to exclude the possibility that H. squalidaria may be a species of the subfamily Geometrinae . There are potentially several Geometrinae species, which live at the sea-level in southern Italy that may be relevant in this context.

H. squalidaria was described by Oronzo Gabriele Costa, the father of Achille Costa, and it is possible that the type specimen(s) of the taxon no longer exist. Turati (1911) visited the Costa Collection in the Zoological Museum of Naples, Italy, and he does not mention squalidaria . Only two wings, thorax and head with an antenna of Megalycinia serraria (Costa, 1882) (Ennominae) are mentioned in the article. Also Conci (1975) reports that part of the A. Costa collection is destroyed. Due to the unavailability of the type material, we are unable to place the taxon squalidaria in the genus Hylaea . We revert it to its original combination, and its taxonomic combination and status are uncertain, being potentially valid at species level and potentially belonging to another genus in the subfamily Geometrinae (see discussion above). We have been unable to trace a candidate for a neotype designation basing on a specimen from southern Italy that would fit well enough the habitus of the figure from the original description.