Hatches Made Easy:

Moths (Geometridae Family) - Inchworms


The inchworm, also called the spanworm, looper, and measuring worm, is the
larva stage of life for the moth. There are numerous species of them in the
Great Smoky Mountains National Park.
Inchworms can be greenish, tan, brown or black. Most of them are green. At
times the worm like larvae will suspend several inches from limbs on a silk thread
they produce. They do this hanging act when they are ready to pupate. It is
common for them to fall into the water. In fact, if they are suspended over the
water, they are going to fall into the water.
A good time to try an inchworm pattern would be when you spot a few of them
hanging from tree limbs, especially during those times when a major hatch is not
underway, which is ninety-nine percent of the time. If you have not seen any of
them on the banks, it very unlikely there will be any in the water.
The different species of inchworms pupate at different times of the year. You will
find them throughout the summer but heavy only at certain times. Once the trout
have seen them, it doesn't seem to matter if they are lots of them or not.
Another big advantage of the flies used to imitate the inchworm is that the same
fly imitates several aquatic insects fairly well. One is the larger net spinning
caddisfly larvae. They also do a very good job of imitating the numerous species
of rock worms, or the free living caddisfly larvae that are very plentiful in the
streams of the Great Smoky Mountains National Park.   

As with most terrestrials, in the larger streams you should fish inchworm larvae
imitations near the banks concentrating on those with overhanging limbs of trees
and bushes. Most of the small stream have tree limbs that about cover the entire
width of the stream. The fly can be fished dry or wet.  
A very good method is to use a large fly such as a hopper as an indicator and
fish the inchworm larvae imitation below it at a depth depending upon the depth
of the water you are fishing. Not only is the large fly a good strike indicator, it
may also get some action from the trout.
Of course you can also use a strike indicator. We almost always fish the fly
without an indicator or a large dry fly tandem rig. You can detect the strike
simply by watching your line and leader.

Just when I finish the aquatic insects for the Smokies and almost degrade the
Great Autumn Brown Sedge, I get email from David Knapp, The Trout Zone,
advising me that he has experienced some very good results with imitations of
them. This reminds me that just because you don't see much activity during the
day from an insect, it doesn't mean the trout want respond to something they get
used to seeing at night. Here is his report. Also, please be sure to check our his

Coming Up Next:
Grasshoppers - (Acrididae/Tettigoniidae)             

Copyright 2008 James Marsh
I just wanted to let you know that I'm still enjoying the "Hatches
Made Easy" and the most recent one got my attention.  Two or
three years ago I had great success in the fall fishing large
caddis patterns.  I would see the adults at night around the
lights at Elkmont and during the day the fish would just slay an
immitation.  One of my largest rainbows in the park ever came
while fishing a large caddis dry that year and then the next day I
had one of my top 5 days ever in the park fishing the same
immitation all day.  Strangely I haven't had much success at all
during that time of year on similar patterns ever since then...  
Any idea if this hatch tends to have "peak" years or something
like that?  Anyway, very interesting information...thanks as
always for doing this as it is a wealth of information.  Hope you
are doing well...

David Knapp