Lower Yellowstone — Hatch Chart

Yellowstone · Highway 89 Bridge to Big Timber / Columbus area

Mayfly Stonefly Caddis Midge Terrestrial | darker = peak activity

Insect Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Size

BWOs (Spring)

#14-16

BWOs (Fall)

#16-22

PMDs

58°

#14-16

Caddis

54°

Midges

Hoppers

#8-12

Ants

#14-18

Beetles

#14-18

Mayflies

BWOs (Spring) Mar–May · #14-16

BWOs (Fall) Sep–Oct · #16-22

PMDs Jun–Jul · #14-16 · 58°F

Caddis

Caddis Apr–May · 54°F

Midges

Midges Feb–Apr

Terrestrials

Hoppers Jul–Sep · #8-12

Ants Jul–Sep · #14-18

Beetles Jul–Sep · #14-18