The Brachycentridae (pronounced: bra-kee-sen-tri-dee) caddisfly family includes one of my favorite genera Brachycentrus, referred to by fly fishermen as the American Grannom or Mother’s Day Caddis. In the northern half of Wisconsin this caddisfly hatch occurs shortly after Ephemerella subvaria (Hendrickson) hatch has dwindled. The Brachycentrus caddisfly hatch is amazing to observe and to fish. and definitely gets the trout’s attention.
Below are some of the characteristics of the Brachycentridae family.
- The tube cases are portable, which allows the larvae to move around looking for food
- Tubes are made of sand and rock fragments or plant materials
- Lack of dorsal and lateral humps on the larva
- The larvae are both collectors and scrapers
Brachycentrus (The American Grannom / Mother’s Day Caddis)
- Chimney-shaped, 4-sided larva cases made from plant parts
- Larvae use a silken tether to control downstream movements
- Larvae prefer fast, running water
- The larvae are typically bright green
- Pupae generally have bright green bodies until exposed to the air
- Brachycentrus emergence seems to start shortly after Ephemerella subvaria
- Adults generally have dark gray-brown wings and drabby olive or brown abdomens
- Mature females have a massive green egg sack
- Females lay eggs on surface, or dive / crawl under water to lay their eggs
- Adult Brachycentrus range in size from size #12 to #16, females are slightly larger in size.
- In Hilsenhoff’s Pine-Popple study he found Brachycentrus americanus, lateralis & numerosus larvae and adults
- Dubois also found Brachycentrus americanus, lateralis & numerosus larvae in his Brule River study.
Some additional information about Brachentridae from Kurt Schmude, Senior Scientist/Professor at University of Wisconsin – Superior
- Some larvae commonly build cases that are round in cross-section, instead of four-sided.
- The specimens of Brachycentrus lateralis that Hilsenhoff reported from the Pine-Popple study were found to be in error. Instead, they were Brachycentrus incanus.
Hilsenhoff, W.L. 1985. The Brachycentridae (Trichoptera) of Wisconsin. The Great Lakes Entomologist 18: 149-154.
- Another common species that occurs in our counties is Brachycentrus occidentalis. The species of Brachycentrus in Wisconsin in order of most common to least common (rare) is as follows: B. occidentalis, B. americanus, B. numerosus, B. incanus, B. lateralis, and B. fuliginosus (which has now been recorded from WI).
- Both B. incanus and B. lateralis occur only in the best of streams in WI.
- We do not know where B. fuliginosus larvae occur because we are not able to identify this species as a larva, yet – only as an adult.
- I should mention that the family Brachentridae has another genus in the family – Micrasema. These genus is much, much smaller than Brachycentrus; mature larvae are only half the size of mature Brachycentrus. However, they build somewhat similar cases. There are three species in Wisconsin: Micrasema gelidum, Micrasema rusticum, and Micrasema wataga. They occur in trout streams and other types of cold to cool-water streams. They are usually associated with aquatic mosses, especially moss on rocks in riffles and runs.
Note: The above is based from my years of observations while on northern Wisconsin trout streams along with several aquatic insect related books.