Case Construction, Movement, Spatial Distribution and Substrate Selection in the Larva of Chironomus Riparius Meigen

Abstract

1. Larvae of Chironomus riparius construct their cases from algae in a stereotyped manner. Mud and a mixture of mud and algae can be used instead of algae, although not so successfully. 2. Larvae cannot build cases from sand, and when presented with this substrate they alternate periods of active swimming with resting on the substrate. This is reminiscent of the behaviour of marine larvae as they test substrates before settling. 3. Larvae space out on an algal substrate. Nearest-neighbour analysis has been used to quantify spacing out, and has shown that under experimental conditions initially clumped animals become regularly distributed over a period of time. 4. As larvae age, they move more slowly and are also less likely to move. 5. In substrate-choice experiments larvae prefer an algal to a sand/gravel substrate. 6. Substrate selection is less marked in old larvae. This could be due either to a loss of ability to discriminate between substrates with age, or to a reduction in the rate of movement with age.