Analyses of the gut contents of larvae of three species of Tanypodinae, collected from four sites in north-east England and Scotland, invariably showed small particles (1-1o ยตm2), predominantly of detritus, to be more abundant than large particles (totoo AM), mostly algae and diatoms . No animal remains, such as carapaces, head capsules and chaetae, or vascular plant fragments were found in any of the intestines . In contrast, food-choice and growth experiments suggested that animal food (particularly Tubificidae and Chironominae larvae) was important in the tanypod diet . In the food-choice experiments, six different foods offered to small (4-7 mm long) and to large (8-12 mm long) larvae of Procladius choreus Meigen, were chosen in the following order: live Tubificidae spp . ; detritus ; live Chironominae larvae ; a mixture of algae and diatoms ; live Ostracoda spp . ; and live Cladocera spp . However, when the results of the individual choices were examined, it was clear that the small larvae had consumed greater amounts of the small types of food (i.e . detritus, algae and diatoms) in comparison to the large larvae . In the growth experiment, those larvae of P. choreus reared solely on Tubificidae, detritus or Chironominae larvae thrived, while those fed on algae and diatoms, ostracods or cladocerans grew more slowly and fewer survived the experimental period . It was concluded that although Tanypodinae larvae are primarily predators with definite food preferences in ideal foraging conditions, in adverse conditions they will utilize a range of available stand-by foods, the most important of which appears to be detritus.