Adeliini Viereck 1918

Tribe Adeliini Viereck 1918, revised rank

Adeliinae Viereck 1918: 69. Type: Adelius Haliday 1833

Diagnosis. Small to minute species, ranging from 0.9–2.7 mm. Antenna of known species with 18 flagellomeres. Occipital carina well developed, complete. Epicnemial carina absent. T1 immovably fused with T2+3; T1–3 not forming a curved, well sclerotized carapace covering all metasoma. Dorsal carina on T1 absent. Spiracle of T6 and T7 absent. Fore wing vein r absent or present; vein r-m absent; vein RS not reaching wing margin. Middle coxa with deep transverse groove.

Included genera. (New World): Adelius Haliday, Paradelius de Saeger; Sculptomyriola Belokobylskij (Eastern Palearctic); Sinadelius He & Chen (China).

Distribution. The Adeliini occur worldwide, although rarely collected (probably due to their minute size and short flight period). The species from Central and South America treated here are the first recorded for the Neotropical Region.

Biology. Solitary, presumably egg-larval endoparasitoids on leaf-mining and bark-mining Nepticulidae, possibly exclusively on that host family. There are unconfirmed host records for other Lepidoptera leaf-mining families (i.e. Gracillariidae, Coleophoridae and Tortricidae, but see Shaw & Huddleston, 1991).

Comments. As discussed by Whitfield & Mason (1994) and Dowton & Austin (1998), most, or possibly all, of the synapomorphies of Cheloninae are shared with Adeliini. The strongly sclerotized and curved T1–T3 forming a carapace-like metasoma is considered the only apomorphy of Cheloninae, but Dowton & Austin (1998) suggest this as a plesiomorphic character in the clade, lost by the most derived group corresponding to adeliines. The absence of the fore wing vein r is considered an autapomorphic character for Adeliini. Some species however, have the vein r present, although short. Adeliini can be distinguished from other Cheloninae by the absence of the fore wing vein r-m, the metasomal terga 1–3 not forming a strongly sclerotized carapace, by their minute size, and by parasitism of Nepticulidae (other chelonines mostly parasitize tortricoid or pyraloid larvae but never nepticulids). Even though Adeliinae has been commonly treated as a subfamily, the phylogenetic evidence suggests that this lineage would be better classified as a tribe of Cheloninae.