The genus Amerila Walker, 1855

In the literature, the taxa dealt with here have usually been placed in the genus Rhodogastria Hübner, 1819, on the basis of a misidentified type-species (e.g., Hampson, 1901; Strand, 1919; Gaede, 1926; Pinhey, 1975; Muller, 1980). The correct type-species of Rhodogastria is, however, Phalaena amasis Cramer, 1779, an African member of the Spilosominae (Watson et al., 1980: 170; Goodger & Watson, 1995).

The genus Amerila (Rhodogastria auct.) has always been placed in the subfamily Arctiinae (e.g., Walker, 1855; Hampson, 1901; Rothschild, 1914; Gaede, 1926; Koda, 1987; Goodger & Watson, 1995), generally close to genera like Axiopoena, Pachyphilona (= Migoplastis), and Utetheisa. However, a separate subfamily "Rhodogastriinae" was proposed by Kiriakoff (1950) consisting of Amerila and the neotropical genus Pelochyta, based on joint distinctive characteristics of the metathoracic tympanic organ.

Since the previous comprehensive taxonomic revision of the genus by Hampson (1901, 1920), which also included the Indo-Australian taxa, several new species have been described from Africa (e.g., Berio, 1935; Pinhey, 1955; Kiriakoff, 1954). A subset of the African species formed the subject of a university thesis project by Muller (1980), which also included the description of a number of new taxa. Muller's thesis (1980), however, has never been published and, accordingly, the new names proposed by him are not available according to article 9 of the ICZN. A catalogue of all species-group names referable to Amerila and information on the nomenclatorial status of all the taxa and their respective type-material has been provided by Häuser (1993). A new catalogue of African Arctiinae (Goodger & Watson, 1995) lists 43 available species-group taxa for Amerila, but omits two names published by Bethune-Baker (1925).

Although Amerila moths can generally be easily recognized even in the field by a characteristic phenotypical appearance (Gestalt), it is difficult to state specific external characters which universally distinguish Amerila species from other members of the Arctiinae. Generally, adults of Amerila can be characterized as follows: medium to large sized (wingspan 17-32 mm) and quite robust; proboscis particularly well developed; antennae filiform in both sexes, black, dark brown or red; forewings elongated, comparatively narrow, often fully or partly transparent medially; hindwings much shorter than forewings, generally weakly scaled; ground coloration of head and thorax white, grey, or various shades of brown, contrasted with a characteristic, aposematic pattern of black dots; in most species, dorsally, one black spot medially on the occiput, two on the patagiae, one or two on the tegulae, three pairs on the thorax, and two on the forewings on the base of the subcostal/radial veins; laterally, two black spots on the pleural region of each abdominal segment; coloration of abdomen dorsally and of inner parts of femora, tibiae, and tarsi often red or yellow.

Additional features with a higher diagnostic value, which might be autapomorphic for the genus, are found in the structure of the tympanic organ (see Kiriakoff, 1950), and in the male genitalia (Fig. 1): uncus and saccus are generally small; in most species the valvae possess on each of their outer surfaces a protrudable, tube-like, often hirsute corema (Plate 1A) (Bethune-Baker, 1925), which can be expanded through the tracheal system; on the inner side they bear a single, strongly sclerotized spine-shaped process. In the female,  the additional postabdominal accessory glands which are generally located dorsally within the papillae anales and otherwise are characteristic of the Arctiidae (Holloway, 1988: 2) are absent (Koda, 1987).

Genital.GIF (4658 Byte)

Fig.: General organization of male genitalia of Amerila, exemplified in A. bubo

 

Generic synonymy

Amerila Walker, 1855: 725.Type-species: Sphinx astreus Drury, 1773, by subsequent designation by Hampson (1900: 60).
Canopus Walker, 1855: 747 (invalid homonym).Type-species: Canopus bubo Walker, 1855, by subsequent designation by Hampson (1900: 60).
Phryganeomorpha Wallengren, 1858: 214.Type-species: Chelonia madagascariensis Boisduval, 1847, by original designation.
Amblythyris Mabille, 1879: 137.Type-species: Amblythyris radama Mabille, 1879, by subsequent designation by Hampson (1900: 60-61).
Euthoracia Hulstaert, 1923: 411. Type-species: Caryatis syntomina Butler, 1878, by original designation. Syn.n.
Gastrochrysia Kiriakoff, 1954: 186. Type-species: Gastrochrysia lineolata Kiriakoff, 1954, by original designation. Syn.n.