oa Journal of the Entomological Society of Southern Africa - The dispersal of Chironomidae larvae : a review



This paper surveys the early classical and recent literature (including 1976) on the benthos of lakes and reveals that density fluctuations of larval Chironomidae within the sediments occur frequently. The chironomid imago generally exhibits poor powers of flight and oviposition site selection. It is left to the first instar larva to disperse throughout the system and to select substrates upon which to live. Dispersal is achieved passively by wind induced water currents; larvae exhibiting adaptations for a planktonic existence by way of positive phototaxis and an ability to feed whilst in the plankton. Later instars also regularly leave the substrate under conditions of environmental deterioration. Planktonic activity also occurs in streams and rivers in the form of drift. In this case, larvae have been demonstrated to have poor powers of returning quickly to the substrate, and can be grouped in the category of """"catastrophic drift"""". Downstream drift is compensated for by upstream rheotaxis of young larvae. This planktonic behaviour enables the group to rapidly exploit new environments and to successfully colonise both temporary and intermittent habitats.


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