The feeding habits of certain chironomid larvae (subfamily Tendipedinae).

SUMMARY1 The nature of the food and the feeding mechanisms of various chironomid larvae with different modes of life have been studied by observing their feeding behaviour in the laboratory and their gut contents in nature and under experimental conditions. 2 Of Tendipes (=Chironomus) larvae, only T. plumosus employs a filter‐feeding mechanism with a salivary net spun across the lumen of its tube anterior to the body. Other larvae of the plumosus ‐group (e. g. T. dorsalis ), although identical in larval morphological characters, feed only on organic matter in the mud. The possession of the unique and complicated feeding behaviour should be regarded as grounds for retaining T. plumosus as a species distinct from the others resembling it in larval characters, some of which are doubtfully valid. 3 Tendipes larvae of the thummi and bathophilus types have no filter‐feeding mechanism but also ingest the mud; this is true too of mud‐living Tanytarsini, e. g. Micropsectra, Tanytarsus (Tanytarsus), Sergentia . 4 Larvae of Tanytarsus (Rheotanytarsus) are filter‐feeders making use of the natural flow of a stream to bring them suspended particles which form their food. The filtratory salivary net is slung between spreading arms built by the larva at the entrance to its tube. 5 Larvae with portable cases (e. g. Stempellina, Lauterborniella) feed on particles of algae or detritus in the vicinity. 6 Chironomid larvae mining in aquatic plants employ a filter mechanism for obtaining their phytoplanktonic food. Like Tendipes plumosus larvae, they spin a salivary net across the lumen of their burrows but, unlike them, turn round after having spun the net so that, while driving a water current through the burrow and thereby catching phytoplankton, the net is posterior in the. The net is also a much deeper cone than that of T. plamousus . 7 Three genera of filter‐feeding leaf‐miners were studied: Endochironomus and Pentapedilum . The genera show certain constand differences in the details of their feeding behaviour for instance in the shape of the net, method of its construction, defaecation behaviour, and extent to which filter‐feeding is obligatory. These differences are described. 8 The rhythm of the feeding behaviour is not conditioned by the amount of plankton being caught in the net. The length of time spent in irrigating during each feeding cycle is, however, negatively correlated with the rate of undulatory body movement during irrigation. The larvae only defaccate whilst feeding: the length of interval between successive defaecations is proportional to the amount of food eaten. 9 The possible origins of the various filter‐feeding mechanisms in Tendipedinae are discussed.