Life cycle and diet of Zygonyx iris insignis (Insecta: Odonata: Anisoptera) in Hong Kong running waters

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Abstract
Zygonix iris is widespread in tropical Asia, and larvae are sprawlers/clingers on rock surfaces in fast-flowing streams and rivers. In the Lam Tsuen River, Hong Kong, this species is univoltine; emergence occurs prior to the summer monsoon and larval recruitment during the wet season. Studies on larval dietary composition in four habitats indicated that Z. iris is a generalist predator, consuming epibenthic prey taxa in proportion to their abundance in the environment. Larval Chironomidae (Diptera) and Baetis (Ephemeroptera) were the commonest food items at all sites and there was little consistent evidence of preference for individual taxa. Larger Z. iris larvae tended to consume more prey taxa than did smaller larvae, and Baetis prey size was positively correlated with predator size. No size selection of chironomid larvae was apparent. Despite its unusual larval habit, Z. iris is a generalist feeder resembling lotic and lentic temperate-zone Odonata.