Thyridoidea

List of Genera: please refer to the 'Checklist' Menu Section for the list of thyridid genera in SE Asia

The Thyridoidea exhibit considerable phenetic heterogeneity and they may not be a monophyletic group (Whalley, 1976). Some are small and delicate but many are robust. The antennae are typically minutely ciliate but may be ciliate, dentate or pectinate (see Text Fig. 2). The wings are broad and typically reticulated with a similar patterning on both FW and HW and sometimes show distinct hyaline patches (fenestrae).

The biology and phylogenetic affinities of this family are poorly understood. Thyridid species are rare in collections and usually seen in low numbers in the field and in light trap samples. Of nearly 14,000 moths from the lowland forest of Sabah, Borneo whereas the tympanate superfamilies and especially the five families: Arctiidae (10.5%), Geometridae (13.3%), Noctuidae (c. 19.5%) and the pyraloid families (Crambidae (17.6%) & Pyralidae (6.0%) were found to make up the majority of the taxa caught (67%) only 1.94% of the morphotypes (>1.7% of the genera) were thyridids (Whitaker & Kitching, 2008; Kitching & Whitaker unpublished data). This rarity was discussed by Whalley (1976: 10-11) who wondered if they are really rare or whether their behaviour renders them less likely to be caught by normal collecting methods.

It is therefore not surprising that little is known about their life history and immature stages and that much of what is known is based on a few Palaearctic and Nearctic species (Darling, 2003). Common (1990) estimated that the group consisted of about 600 species in about 180 genera but this estimate should be increased considerably. There are probably in excess of 760 named species, together with 450+ undescribed spp. and sspp. in the NHM collections as estimated by Shaffer in 1999 (in Dugdale et al., 1999). In 2009 the LepIndex listed 1309 names comprising approximately 779 species including about 24 species (c. 37 names) in the Charideinae. Over 290 species are known from SE Asia, and dealt with in this volume. By comparison RTS in 1994 cited only 240 species. There are additionally 55 from Australia (Shaffer & Nielsen, 1996), as well as 24 species from Japan. (Inoue et al., 1982).

Whalley (1976) has defined the Thyridoidea as follows: External ocelli are rarely present. Proboscis when present is scaleless. Chaetosemata are absent. Maxillary palps are minute and hidden under scale cover. Labial palpi usually three segmented, sharply up-curved, with a short apical segment. Epiphysis rarely absent. Wing venation is little reduced (see Text Fig. 6 above). Fore wing with twelve veins, vein R5 to termen and no areole. The veins Rs1 to Rs4 usually arise independently from the cell but sometimes Rs1 & Rs2 and Rs3 & Rs4 may be stalked. Hind wing with Sc + R1 and Rs approaching closely and sometimes joining for a short length and with two anal veins (See Table 1 above). Abdominal tympanal organs are absent. Cephalic vestiture appressed. The frons of some species is occasionally extended into a prominent process. Wings often yellowish brown with a strongly reticulate patterning. Some species have large hyaline fenestrae in the wings. A frenulum is very rarely present. Hind tibia with one or more pair of spurs (formula 0-2-2, 0-2-3 or 0-2-4) and the males may have hair pencils on their hind tibia.

Dugdale et al., (1999) list several other probable autapomorphies: Tergum 1 has large lateroventral lobes immediately behind the spiracle. The resting posture is with mid-legs not touching the substrate. Spinarea are absent and the HW has CuP vestigial. Thyridid adults often rest with the body steeply raised and the wings held outstretched and mid-legs not touching the substrate, a posture shared with many members of the Pyraloidea (Kristensen 1998: 228).

The first division of the family Thyrididae (Herrich-Schäffer, 1846) = Siculodidae [as Siculides] Guenée, 1877) into subfamilies was by Guenée (1877) and subsequently used by Pagenstecher (1892). These divisions, effectively Pachythyrinae, Striglininae, and Siculinae, were ignored by subsequent authors until Whalley (1964, 1967, 1971a), who separated the family into four subfamilies; Argyrotypinae, Striglinae, Pachythyrinae and Siculinae. (Whalley, 1976). Scoble (1992) recognised five subfamilies: Thyridinae, Argyrotypinae, Pachythyrinae, Striglinae, and Siculodinae but subsequently considered the Pachythyrinae as synonymous with Thyridinae (Scoble, 1995). The Argyrotypinae (sensu Whalley, 1967) containing the African genera Chrysotypus (Butler, 1879) and Neochrysotypus (Whalley, 1971a) is now considered synonymous with the Siculodinae but the monophyly of the subfamily is not proven.

Currently the Thyridoidea is considered to have a single family, the Thyrididae. The monophyly of the Thyrididae, including Siculodinae, is based on at least four apomorphies of the adult (Minet, 1991). This family is currently classified into four subfamilies (Siculodinae, Striglininae, Thyridinae & Charideinae) by Dugdale et al. (1999), who give a key to the subfamilies, reproduced below.

The Charideinae are a small group of about 37 species of Afrotropical, diurnal, narrow winged moths. With their metallic, aposematic colours and scanty resemblance to typical thyridids they were long included in the Zygaenidae, from which they were transferred by Minet (1991) (Dugdale et al., 1999) as a subfamily of the Thyrididae.

Species belonging to the subfamily Siculodinae (sensu Minet, 1991) have possible tympanal organs situated in vein Sc at the base of the fore wings; this presence of alar tympanal organs is an autopomorphy for the Siculodinae (Minet, 1983, 1985, 1988).

Whalley (1971a) distinguished the tribes Opulini (usually no apical spines on the tarsal segments, but in a few species spines may be present on the last tarsal segment of the hind leg) and the Rhodoneurini with paired apical spines on tarsal segments. However, following Shaffer & Nielsen (1996), we consider the Siculodinae as comprising three tribes: the Argyrotypini, Rhodoneurini and the Siculodini, with Opulini and Siculini as synonyms of the Siculodini.