.......................  ....................  ...Fly Fishing Yellowstone National Park

New KISS Bug Series - Part 21

The Little Black Caddisflies

Much like a mayfly, the Little Black Caddis newly hatched adults are sometimes eaten on the surface
before they depart the water. As I wrote in the pupa article, I think many more pupae are eaten than adults
but that doesn't mean that the trout won't take a dry fly imitation of the adults. They will do just that. Many
anglers use the dry fly exclusively during the hatch simply because they prefer the dry fly fishing

occidentalis species are a hook size 18 but the males are a little smaller. Although I've read where
these caddisflies are larger in Yellowstone, I have not found that to be the case at all. We use the hook size
18 because the females are the ones that deposit eggs and the egg laying event is the highlight of the

Normally the water is fairly cold, approximately 50 degrees F., when these caddisflies hatch. The cooler
water does cause them to have to ride the water for a short time before they fly off to the banks.  
Sometimes, it's so cold in the mornings during the hatch that the adults are almost dormant. I have seen
many occasions when you could pick up several of them off of the rocks and plants as they made no
effort to fly away. On cold days, it's usually mid-afternoon after a hatch has started before the adults start
flying. On these cold days, the hatch will start during the warmest part of the day.

americanus species that hatch during the late Summer and early Fall ride the water for only a short
time. Your usually better off fishing the pupa imitation during the hatch and the adult imitation when they
are laying eggs.

As mentioned before, the adult females usually start the egg laying process prior to the end of the hatch.
When this happens, maybe an hour or two, there are usually a lot of caddisflies on the water. The females
either deposit their eggs on the surface of the water, or dive and deposit the ball of eggs they carry. The
trout eat them in both cases. They ones that dive return to the surface of the water for a short time before
flying away.

When the egg laying first starts, the most productive fly is usually still the pupa imitation. At some point, the
hatch will stop and things change. At that time, I suggest you try a dry imitation of the egg layers.

You should fish the adult dry fly in a dead-drift fashion where you see the most activity. Most of the time, I
fish the adult fly down and across. Usually the dry fly works great but factors such as the water and air
temperature can affect the activity and results.

Very late in the day, near dark, there may be a lot of spent caddisflies on the water. They usually collect in
the eddies and slow, calm pockets along the banks. In this case, this is where you want to fish the adult
pattern. Sometimes the trout will rise to it when it's just drifting slowly around in circles in the eddies. They
will also collect at the heads of the pools below the riffles and runs.
Copyright 2012 James Marsh
Little Black Caddis:
Availability to trout:             
Hook Size:                          
Type of water:                    
Emergence time:                
Duration of hatch period:

Brachycentrus occidentalis, B. americanus
Cassed Caddis (Short-horned Caddis)
Moderate to slow - smooth and broken surface
The real one