Diptera (flies), Homoptera (planthoppers), Hymenoptera (social insects), Isoptera (termites), and Coleoptera (beetles) were the most numerous prey in 32 food boluses being delivered by parent White-rumped swiftlets (Aerodramus spodiopygius) to their chicks inside two Fijian caves. Numerically the main food items were flies (37%) and planthoppers (33%). Both the season and the habitat over which the birds had been feeding seemed to determine whether flies or planthoppers predominated in a particular bolus sample. Flies predominated in the prey of swiftlets foraging over open country, whereas planthoppers predominated in the prey of swiftlets foraging over both forest and open country. The number of insects in each food bolus ranged from 47 to 750 (mean = 236). The average weight of a bolus was 0.225 g (range 0.1- 0.43 g). The average length of all prey was 2.48 mm, which is larger than the average length of available prey (1.63 mm). The number of prey species ranged from 2 to 83 (mean = 30 per bolus). Altogether, 167 species were recorded in food boluses. The White-rumped swiftlet bred during the wet season, when insects were more abundant. This study, along with others (largely unpublished) shows for the first time that Hies are often the most common insect in the prey of swifts, swiftlets and swallows.