Acraea Fabricius, 1807

Williams, Mark C. & Henning, Graham A., 2023, Taxonomic revision of the tribe Acraeini Boisduval, 1833 (Papilionoidea: Nymphalidae: Heliconiinae), Metamorphosis 34 (1), pp. 35-49 : 37-38

Genus Acraea Fabricius, 1807

Type-species Papilio horta Linneus, 1764

Synonyms: Aphanopeltis Mabille, 1887 ; Phanopeltis Mabille, 1887 ; Solenites Mabille, 1887 ; Miyana Fruhstorfer, 1914 .

This is a predominantly Afrotropical genus of 31 mediumto large-sized species, four of which occur in the Oriental and Australian Regions. The lineage arose ~ 16 Mya.

Body: Head large, broad and hairy. Antennae shorter than half length of forewing, averaging 45% (41-48%) of forewing for both sexes. Palpi 1 st joint twice as long as broad, 2 nd joint three times longer than first joint and terminal joint minute, oval. All joints hairy. Thorax short, compressed laterally, hairy and scaly. Abdomen long, extending just beyond outer edge of hindwings, laterally compressed, broader distally. Legs: Anterior legs slender and less than half length of pterothoracic legs; tarsi of male single joint without spines, female tarsi five jointed with spines on each except last, no terminal spine. Pterothoracic legs robust, external claw of male furrowed on inner surface, terminal claws asymmetrical. Wing venation: Radial veins of forewing not stalked; R1 branching off from cell rather than stalked. Cell of hindwing slightly more than half of total wing length. Markings: Hindwing with a row of four spots below the apex, three across the centre and two across mid-cell (4-3-2 configuration). These spots may be absent or coalesced into a single patch or into two patches. Hyaline areas and hyaline patches present. There are no marginal markings or spots on forewing upper side. Male genitalia: Uncus beak-shaped and elongate, acute or bifid at tip; aedeagus long, narrow and needle like; sclerotized and modified 8th sternite present, distally lobed velum, may have distal tooth; valves subtriangular, pronounced dorsally; juxta elongate, triangular, weakly sclerotized; vinculum fairly broad; saccus small. Female genitalia: Anal lobes small, posterior apophyses slightly longer than lobes; sterigma usually taking the form of a large plate; ostium centrally or posteriorly placed; ductus short and sclerotized; bursa ovoid or spherical; single pair of signa, very small or absent. Sphragis present except in A. satis species group.

Early stages: Egg ovoid; almost as broad as high, sometimes taller; laid in clusters. Larvae gregarious. Pupa often extensively marked with black. Host plant genera: Rinorea (7 records), Passiflora (3 records), Corchorus , Turnera , Kiggelaria and Adenia (2 records each). There are single records for Gymnosporia , Lauridia , Rawsonia , Premna , Smeathmannia , Ceratiosicyos , Guthriea , Camellia , Gossypium , Vitis , Barteria , Basananthe , Hibiscus , Hybanthus , Ipomoea , Nicotiana , Tricliceras , Drypetes , Tylophora and Scepocarpus . Host plant families: Violaceae (7 records), Passifloraceae (4 records), Turneraceae and Achariaceae (3 records each), Malvaceae (2 records). Single records for Celastraceae , Flacourtiaceae, Verbenceae , Theaceae , Vitaceae , Convolvulaceae , Solanaceae , Euphorbiaceae , Apocynaceae and Urticaceae . Habitats (biomes): Predominantly a forest genus, with one species in arid savanna. Wet forest (10 spp.), submontane and montane forest (4 spp.), coastal forest (3 spp.), dry forest (4 spp.), woodland (4 spp.), savanna ( A. neobule ) and very dry savanna ( A. brainei ). Geographical range: The genus occurs throughout the Afrotropical Region and there are four species in the Oriental and Australian regions. On the mainland the genus is best represented in east-central Africa ( Tanzania, southern and eastern DRC, Uganda and Kenya) and west-central Africa ( Nigeria, Cameroon, Gabon and Angola).

Diagnosis

Facies: In the genus Acraea the hindwing has a row of four spots below the apex, three across the centre and two across mid-cell (4-3-2 configuration). In the other African genera the spots in the row below the apex are joined to the central row creating a discontinuous arrangement of spots (7:2 configuration). These spots may be coalesced into a single patch or into two patches. Hyaline areas and hyaline patches present on fore- and hindwings. There are no marginal markings or spots on forewing upper side.

It would be pertinent to mention here that as the Acraeini are both models and mimics, and in particular they mimic themselves, various patterns can be found repeated across several of the genera. Examples would be Acraea quirina , Rubraea cerasa and Telchinia orestia ; also Tildia zetes , Rubraea egina , Stephenia rogersi and Telchinia pharsalus . These Müllerian mimicry rings are found throughout all the genera of Acraeini and could lead to some confusion with regard to the use of facies in establishing a diagnosis.

Genitalia: The male genitalia in all Acraea have extra modifications. In the horta species group the 8 th sternite is modified to form a protective plate called a velum. In the machequena species group the valves are strongly incurved, forming a claw. In the satis species group the 8 th tergite is produced into a pseudouncus, with the rest reduced in size. In the admatha species group the juxta is articulated by a transtilla and connected by an elongate sclerite. In the quirina species group the uncus is divided into two hooks as large as the valves. The female genitalia have the sterigma usually taking the form of a large plate.

Species list