Central Wisconsin trout streams just completed their Hex mayfly hatch, the hatch of the largest mayflies in the Mid-West which are up to two inches in length from head to end of tail. The next significant hatch from these streams is that of the smallest mayflies fishers attempt to imitate with their flies - the Trico hatch. These tiny bugs are barely three eighths of an inch in length and most of that length is in their nearly invisible tails. There is no smaller mayfly commonly sought by fishers in our area. It is small on several scales: size of individuals, therefore being difficult to locate when swarming and it is in the small hours of early morning that they must be fished. The very opposite of the Hexagenia in size and behavior.
The name Trico is a shorten version of their Latin name Tricorythodes. In Central Wisconsin, Tricos do not form huge clouds of spinners that are observed over western rivers because we lack large coldwater rivers with extensive weed bed habitats. Rather the spinner swarms are sized smaller for our smaller streams. Streams with vegetative islands of veronica and elodea plants are worthwhile to investigate prior to July hatches to locate future fishing areas. Larvae prefer the slower current flows within the plant layers comprising islands of vegetation. They cling to leafy structures feeding on algal growths and organic materials that settle out of the passing current. Larvae can be found by swishing a handful of leaves within a container of water, which dislodges them for easy recognition. The other tried and true search method, applied after the hatch is underway, is surveying spider webs for entangled spinners at bridges and along streams. This method works well since the hatch usually extends over a four week period.
Tricos have a unique emergence and mating practice. Males emerge under cover of darkness and remain in the dun stage hiding out overnight within stream side vegetation. Female duns emerge in early morning and immediately molt to the spinner stage. During these early hours, as the sun warms dew soaked shrubs and bushes, males from the previous evening transform to the spinner stage and take to the wing forming aerial swarms above the stream margins. Female spinners fly into the swarms of males and mating follows during flight. Egg laying occurs almost immediately and spinners of both genders fall to the stream. In several morning hours the hatch and spinner fall is over.
When fishing it is near impossible to see spinners on the water; however, the trout will see them and alert you to the correct location by their rising. Depending on current configurations, foam lines may form collecting drowned spinners which again trout will signal by their gulping feeding behavior. Trout can become very selective, therefore tie a collection of fly patterns specific to male (all black bodied; wings clear; smaller than females) and female (black thorax and cream abdomen; wings clear; larger than males) genders within a size range of #18-#24. Battered and beaten flies fished wet produce surprisingly good results toward the end of the daily hatch.
Summer Trico fishing is really quite wonderful, in that fishing occurs before the heat of day. Some of my earliest and most fond memories of fly fishing occurred watching the first rays of sunlight convert dew into a fog that drifted over the river and transformed into swarming Tricos.
