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The difference between a Caddis Pattern and a Nymph Pattern

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Just curious is a Caddis Pattern considered a Nymph Pattern or are they different? To me they pretty much look similiar in design.

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Although the patterns can be very similar, there are fundamental differences between the immature stages of the mayfly (nymphs) and the caddisfly (larvae and pupae.) Most important to the fly fisher are the differences in availability and behaviour of these insects. Knowledge of the lifecycles of the naturals can be used as a guide to the presentation of our flies.


Mayflies have what is called incomplete metamorphosis. The stages are: egg, nymph, the subimago (dun), then imago (spinner). (Its called incomplete because there is no pupal stage.) The nymph eats and as it grows it passes through a number of instars (where it sheds its old undersized exoskeleton and grows a new, larger one.) After the final instar, the nymph either swims to the surface or crawls out of the water where the adult (dun) climbs out of final nymph husk and flies off, usually to nearby vegetation, to shed its skin one last time and become the sexually-ready spinner.


Caddisflies have complete metamorphosis (like butterflies.) The stages are: egg, larva, pupa, adult. Like the mayfly nymph, the larva passes through a number of instars as it grows. However, after the final instar the larva (in most species) wraps itself in silk and enters a quiescent stage (the pupa) where it transforms into the adult. When transformation is complete the pupa (usually) swims to the surface, aided by an envelope of gases trapped under the pupal shuck.


Nymphs of different species exhibit a range of behaviour: Some are burrowers, spending most of their "childhood" burried in mud, and are pretty much unavailable to the trout. Until emergence when they make the journey to the surface. The nymphs of some species are agile swimmers, behaving much like tiny fish. Others cling to the bottom of rocks. The larvae of different caddisfly species also exhibit a large range of lifestyles: Many build a case of stones or sticks in which to hide. Some build little silk tents on the stream bottom and catch their meals in tiny silk nets. One family roams free, often rapelling from one site to another attached to a silk lifeline.


In short (and I apologize for not being...): It helps to know the details of the lifecycle of the natural you are imitating.



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Rockworm gave you a great over view of the lifecycles


Here’s some examples of patterns that imitate different stages in the life cycles that you’re probably familiar with or can google:


May fly

Mayfly Nymphs- imitating the larval form Most popular patterns are the Pheasant Tail Nymph and Gold Ribbed Hares Ear. The naturals have either 2 or 3 tails.


Mayfly Emergers imitate the nymph transitioning into the dun. They can be tied to fish under the surface like wet flies such as soft hackles (Partridge and Orange), winged wet fly patterns (Hare’s Ear Wet, Leadwing Coachman Wet), and nymph looking patterns on a dry fly hook with a short tuft wing of CDC, Poly Yarn, or SnowShoe Hare (Snowshoe Hare Emerger) or ride on top of the surface like Sparkle Duns which have a “tail” of Z-lon that is designed to imitate the dun still attached to its nymphal case (called a “shuck”)


Mayfly Duns- standard and parachute dries like Adams, Blue Wing Olive, March Brown, Light Cahill and modern patterns like Comparaduns. Most Mayfly wings are tied upright.


Mayfly Spinners- Rusty Spinner in various sizes imitates the final stage of the lifecycle of many mayflies. This is when they mate and the females return to the stream to lay eggs and then die. The wings are typically tied “spent” lying horizontally on the water in the film.



Larva patterns imitate species that are free living, and those that live in cases made of sticks and twigs or gravel. You’ll often find caddis cases on streamside rocks. The only caddis larva pattern I carry is the Rockworm, A free living (no case) caddis larva that is found in riffles all over the country-


Some folks also carry imitations for caddis larva that live in cases like the Peeking Caddis http://www.flyanglersonline.com/flytying/fotw/040300fotw.php


Pupa patterns can be very effective swung in the current and fished as a wet fly searching pattern in rivers that have a lot of caddis. They imitate the emerging stage of the caddis as it swims to the surface. Emergent Sparkle Pupa is a very popular pattern that imitates this stage of the caddis http://www.virtualflybox.com/patterns/patt...d=23&id=172


Adult caddis imitations include dry fly standards like the Elk Hair Caddis. They have wings that slant back to the bend rather than upright wings on mayflies.


Stoneflies have just 2 stages the larva (nymph) and adult. They have 2 tails in both stages. Most stonefly nymphs crawl out of the water and molt into adults on land, so there is no emeger stage.


Stonefly nymphs (larva)- Kaufmanns Stonefly Nymph is a good example


Adult- Stimulators, Salmon Fly are good examples of dry fly patterns. They have wings that slant back like caddis.


Some nymph patterns, like Prince Nymphs can be very effective because they look sorta like a lot of different things- dark mayfly nymphs, cased caddis and small stonefly nymphs.


Some patterns like soft hackles and winged wets do a good job of covering both emerging mayflies and caddis and the drowned adults.


If you want to see some pics of the naturals in various stages and learn a bit about the behavior and lifecycles, www.troutnut.com is a great site.



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Wow thanks. :bugeyes: I thought my Fly fishing books were informative. Both of you did a pretty good job covering the question. I'm still reading threw the replies. I feel like I just came out of my Biology class back in High School. Don't remember much though, I was to busy staring at my teacher :devil:

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