Upper Jefferson — Hatch Chart
Jefferson · Twin Bridges (Big Hole / Beaverhead confluence) to Cardwell area
Mayfly
Stonefly
Caddis
Midge
Terrestrial
| darker = peak activity
Insect
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Size
Mayflies
BWOs (Spring)
Mar–May
· #14-16
BWOs (Fall)
Sep–Oct
· #16-22
PMDs
Jun–Jul
· #14-16
· 58°F
Tricos
Jul–Sep
· #18-22
Stoneflies
Yellow Sallies
Jun–Aug
· #8-16
Caddis
Caddis
May–Aug
· #12-16
· 54°F
Midges
Midges
Jan–Dec
· #18-26