December
High country
The swimming mayfly nymph (Nesameletus) becoming more common. Coloburiscus hatches starting to die down. Deleatidium hatches still occurring - generally the smaller species with non-mottled wings (D lillii, D vernale). Horn caddis common, and hatching during the evenings. Free living caddis and net building caddis common, and hatching. Stone cased caddis also common. Stoneflies uncommon. Green beetles becoming abundant as the month progresses. These are more important in lake fisheries, but on windy days, can be an important food source for river trout. True flies are also becoming more common. Oniscigaster mayfly nymphs still present.
Low country
Brown beetles becoming less common, with evening feeding focusing on caddis adults. Most species of caddis hatching, especially Aoteapsyche (a mottled brown wing, 15mmlong with a dark brown body) and Olinga (greyish yellow wings 10mm long with a dark brown almost black body). Horn caddis and sand cased caddis larvae an important food source during the day. Deleatidium hatches sporadic. Willow grubs starting to mature, and trout will focus on these during the day as the month progresses. Chronomids important in silted rivers.