Egg and Larval Development Times for 35 Species of Tropical Stream Insects from Costa Rica

Abstract

We examined total development times for 5 mayfly species, 2 stoneflies, 10 caddisflies, and 18 chironomid midges collected from three streams that flow through tropical evergreen forest in northwestern Costa Rica. Most eggs, larvae, and pupae were reared in the laboratory in a photoperiod of 12:12 LD and at 20°C, which simulated field conditions. Algae, algal detritus, and leaves were provided as food for all species; predators were also given various animal prey. All study species had total development times that were rapid relative to the univoltine life histories observed or assumed for many temperate species. Egg development times ranged from a few days to approximately a week for chironomids and from 10 to 38 days for mayflies, stoneflies, and caddisflies. Most chironomids had short larval/pupal development times: development was completed in 19-29 d by seven species, in 30-40 d by nine species, and in >50 d by two species. Relatively short development times (including the pupal stage when present) were also observed for the mayfly Acerpenna sp. (28 d) and the caddisflies Wormaldia sp. (45 d) and Oecetis nr. prolongata (52 d). Larval/pupal development times were longer for the other four mayflies (76-159 d), two stoneflies (83-167 d), and eight caddisflies (72-209 d). No evidence of egg or larval diapause was observed. The combination of rapid development and absence of diapause suggests that all these species have multivoltine life histories. This finding has important implications for temporal changes in the structure and function of the aquatic insect assemblage in these streams.