Caddis Larvae--Part II

By Jeff Morgan

This is the second part of an article on imitating caddis larvae. Caddis Larvae--Part I discussed cased caddis. Part II focuses on uncased caddis.

Green Rockworm

Green rockworms (green caddis larvae) draw a lot of attention from anglers, perhaps because they have a common, recognizable name. The attention is unwarranted, and should be directed to other green colored larvae, especially netspinners (spotted caddis , genera Cheumatopsyche and Hydropsyche), and grannoms . Nonetheless, a nymph box without green rockworm imitations is like a golf bag without a sand wedge: when you need one, you really need one.

A perfect rockworm pattern is hard to create. The insect is a translucent bright green shade that I can't seem to find in a commercially available dubbing. They also have a reddish-brown head that is small and translucent. In addition, they are heavily segmented, especially when they are contracted while drifting. Natural rockworm larvae have very small legs as well, relying on their anal hooks for movement.

Many of the traditional patterns have been too thick, too drab, or too "flat" (lacking segmentation), so there is definitely room for yet another green rockworm pattern.

This Rockworm pattern uses a shellback of clear Body Stretch which enhances the appearance of segmentation, as well as making the pattern a little shinier underwater. It also adds to the illusion of a translucent body. The legs are not necessary, but I like short legs on the fly for aesthetic reasons.

This is certainly not the last word on green rockworm larvae, but it may give you some things to think about as you create imitations of your own.

This fly is best in spring because most green caddis larvae hatch from the egg in January or February and grow to maturity, and then pupate by June. Start with a size 18 imitation in March and move to a size 12 or 10 by May and June. Fish green rockworm imitations in swift riffles and pocket water.

Big Grub

The Big Grub imitates the large Parapsyche or Arctopsyche caddis larvae. The fly was designed for the small streams where these insects are common. I'm a strong believer in big flies, such as adult cranefly imitations, on small streams because they keep small fish off the hook. They can also move trout a long way, since a big chunk of food justifies the distance covered to obtain it.

Previously, I used golden stonefly nymph patterns for my main small stream nymph. Now I like these big caddis imitations. They are simple to tie, unique (virtually nobody imitates them), and break up the monotony of churning out the same old thing every day at the vise.

These patterns can double as an impromptu cranefly larva imitation on streams where the caddis are not found, so they are worth carrying everywhere. The fly's construction is virtually the same as the Little Netspinner (below), requiring little extra in materials.

Little Netspinner

On the Oregon's Deschutes all you hear about are the "green rockworms," yet that caddis species is outnumbered about 10-1 by netspinning caddis (spotted caddis ). The bright green color of these Cheumatopsyche larvae can be blamed for their misidentification by many anglers.

The Deschutes is a textbook stream for filter-feeding insects such as this caddis: the river receives water from a spring creek (Metolius River) and a fertilizer-infused alkaline desert stream (Crooked River), AND it is a tailwater! Even better, the basalt rocks lining the streambed form an irregular structure for netspinners to build their nets around.

The Little Netspinner pattern matches the shape, body position, and coloration of the natural much better than the simple-to-tie Krystalflash rockworms and glass-bead bodied rockworm imitations that are most often used on the Deschutes.

Don't pick the body out on this pattern, ala the Net Builder , lest the fly look more like a scud than a caddis larva. You want to maintain the thin profile of the drifting natural.

A black paint pen is a good way to darken the first two segments of the shellback, matching the dark sclerotized shields of the natural.

Inverted Netspinner

Many descriptions of drifting insects, such as Charlie Brooks' "no-tumble" theory (upon which he based his "in the round" style of tying; see the Brooks Stone ) or the idea that caddis and stonefly nymphs curl when drifting, do not mesh with current scientific research or my own experience.

I collected several hundred hydropsychid (netspinner) caddis larvae of several genera on different rivers to see how they reacted when drifting. The most common behavior of the larvae was not to curl up in a ball or even to slightly curl. Instead, they arched their backs and drifted in an inverted manner. While looking odd, it makes sense: the position exposes their legs and anal hooks, allowing them to grasp the bottom more easily than if they were curled up.

The Inverted Netspinner imitates this behavior. I use a standard netspinner pattern tied upside-down to expose the legs and "tail" (anal hooks). There's nothing really fancy about this pattern except you need a curved-shank hook to match the arched back of the natural.

Matching this body position is not essential to success; past netspinner patterns have been tied with the "normal" curl and have caught fish. However, I have noticed a small improvement with this pattern over traditional ones as the dark thoracic shields, abdominal gills, and color variation of the body make the top appear significantly different than the underside of the insect.


New patterns in this article are:

Big Grub
Little Netspinner
Inverted Netspinner

Jeff Morgan has written many articles for Westfly, mostly on entomology and fly tying. He is the author of An Angler's Guide to the Oregon Cascades and Small Stream Fly Fishing.