Surveys of the aphid and associated insect fauna of The Kingdom of Tonga were conducted as part of a biological control program against the banana aphid, Pentalonia nigronervosa Coquerel, using the polyphagous aphidiine parasite, Aphidius colemani Viereck. Ten aphid species were collected, plus three species of primary parasites (Hymenoptera: Aphelinidae and Braconidae: Aphidiinae); one species of hyperparasite (Hymenoptera: Charipidae); coccinellid, hemerobiid, and syrphid predators (Coleoptera: Coccinellidae; Neuroptera: Hemerobiidae; and Diptera: Syrphidae); parasites of syrphids (Hymenoptera: Ichneumonidae and Encyrtidae); and eleven species of aphid-attendant ants. The aphids Brachycaudus helichrysi (Kaltenbach), Hyperomyzus carduellinus (Theobald), Hysteroneura setariae (Thomas), Myzus persicae (Sulzer), and Toxoptera citricidus (Kirkaldy) are new records for Tonga. Aphis craccivora Koch, A. gossypii Glover, Brachycaudus helichrysi, Myzus persicae, P. nigronervosa, Rhopalosiphum maidis (Fitch), Toxoptera aurantii (Boyer de Fonscolombe) and T. citricidus are all known to be suitable hosts for A. colemani. Compiled distributional data of aphids on South Pacific islands show that these species are present throughout the region, which suggests that A. colemani could be a useful addition to the insect fauna of the region. Aphidius colemani was recovered in 1992 from Aphis gossypii. The hyperparasite Alloxysta darci (Girault) is unlikely to parasitize A. colemani or any other Aphidiinae.