.......................  .................  ......Fly Fishing Yellowstone National Park
4/26/12

New KISS Bug Series - Part 2
Bugs 101

Identifying Bugs:
Probably most of you can tell one type of bug from another but for those who can’t,
or are just getting started fly fishing, let me briefly cover some basics of identification.
An aquatic insect is one that is born and lives most of its life in the water. A terrestrial
insect is one that is born on land and spends all of its life on land, unless it
accidentally falls or is blown into the water.

Aquatic Insects: Mayflies, caddisflies, stoneflies and midges are aquatic insects.

Terrestrial Insects: Grasshoppers, ants, crickets and such are terrestrial insects.

There are other insects that fit into these two categories - damselflies, dragonflies,
crane flies, and so forth, but for the most part, this represents the bugs trout eat.

Trout Bugs 101 is being able to tell a caddisfly from a mayfly from a stonefly from a
midge. Lets look at these in their larval stage of life.

Mayfly Nymphs:
Mayfly nymphs have either two or three tails. They can be easily confused with
stonefly nymphs. If you are not sure, check their legs.
Mayfly legs end with a
single claw and stonefly nymphs with two claws.
Plate like gills are present
along the abdomen of a mayfly.

Stonefly Nymphs:
Stonefly nymphs have two short tails.  Their legs end with two claws. They either
have no visible gills or their gills are found under their head or upper body.

Caddisfly Larvae:
A Caddisfly larva looks like a little worm or if it is a cased caddis, a little worm in a
case with its head and maybe its tail stuck out. They are very easy to distinguish
from a mayfly or stonefly nymph.

Midge Larvae:
A Midge larva is a tiny, worm looking creature that is usually burrowed in the soft
bottom of the stream or lake. They can be confused with an uncased caddisfly larva,
but for the most part, are much smaller. Now lets look at the adult flies.

Adult Mayflies:
Mayfly adults look like little sailboats on the water. The have two, larger upright wings
and can and usually do have two little ones called hind wings.  

Adult Stoneflies:
Adult stoneflies have (4) four wings but they are folded flat on top of the fly and look
like one wing when they are at rest. In the air, they look larger than they really are.

Adult Caddisflies:
Adult caddisflies also have (4) four wings but they are folded in a tent shape when
the fly is at rest. They two look much larger in the air than they really are.

Adult Midges:
Midges are tiny (2) two winged flies that look like mosquitoes. Much of the time they
are difficult to see in the air or on the water. Don’t just assume the small flies you see
are midges. They may be mayflies. Take a closer look.

Summary:
You should learn to be able to recognize these (4) four different types of flies as a
nymph or larva, as a pupa (if this stage of life exist), and as a full grown adult
whether they are at rest, on the water or in the air. There are others, but they are
easy to tell apart, like the crane fly, the dragonfly and the damselfly.  
Copyright 2012 James Marsh
Thumbnails: Click to Enlarge
Mayfly Nymphs
Stonefly Nymph
Caddisfly Larva
Mayfly Dun
Adult Stonefly
Adult Caddisfly