Fly-Tying: Ticking the Boxes – the Humped Back Spawner

On my fly pattern checklist, John Kent’s Humped Back Spawner ticks all the necessary boxes for a deadly freshwater shrimp or scud pattern. The Humped Back Spawner boasts a convincing realistic appearance, instantly appealing to any fly fisher the moment they see it. More importantly, trout view it with equal appeal.


Simple in concept, there are a few design and material considerations any reasonable scud pattern should possess. Although there are two scud families to consider, the larger Gammarus or the minute Hyallela, size is the only distinguishing feature of consequence. Scud patterns tied in a size range from #10 through #16 cover most presentation scenarios.

While straight shank hooks are an excellent foundation, most scud patterns today are tied on curved hooks. No matter the hook choice, it is important to remember that the goal is to impersonate a swimming scud. Swimming scuds swim with a predominately straight body. Only the tip of their body hangs down. Exaggerated curved, c-shaped scuds are dead, resting or feeding. Slightly curved body scuds are acceptable but be careful not to extend the body too far into the bend.


When using curved hooks it important to realize what happens if you weight the midsection. Now the heaviest point on the hook, the weighted midsection causes the hook and your finished fly to roll over, a characteristic often referred to as the keel effect. Metal beads are a better option as the weight is evenly distributed around the shank. When using metal beads keep them small to reduce the keel effect and compliment the overall shape of the finished fly. For example, a size 10 Humped Back Spawner uses a 7/64” metal bead.

There are a variety of body materials suitable for scuds including dubbing, Crystal Chenille and on smaller patterns, ostrich herl. Of these body choices dubbing blends of rabbit, squirrel, seal’s fur and a myriad of synthetic mixes are the most popular. Dubbing not only provides translucency but once brushed or picked out suggests the legs and antenna of the natural scud. Palmered body hackle also does a great job suggesting legs and antenna.


Masters of camouflage; scuds match their surroundings. Common scud colours include olive, grey, olive/grey, yellow/olive and tan. Orange is a common, worthwhile, colour highlight. Orange beads (both metal and glass), thread heads and dubbed midsections are incorporated to imitate either a pregnant or a Gammarus scud infected with a unique orange parasitic worm called Acanthocephalan. The small focused orange spot in the middle of their backs easily identifies an infected scud. Pregnant scuds feature an underslung orange brood pouch that is home to her young. When she next molts, her offspring are released to fend for themselves. Freshly molted scuds range from bright to medium blue colour due to their copper-based blood system. A scattering of blue-based scud patterns is always a good idea.

The distinct armadillo-like back of a scud can be imitated using a number of materials coupled with a wire or monofilament rib. Popular shellback choices include strips cut from plastic bags, Scud Back, Mylar, flat braids, Thin Skin and buoyant materials such as deer hair or foam. Buoyant back scud patterns are a great choice when prospecting around aquatic weeds, as they tend to hang up less. Frostbite makes an excellent shellback material on tiny scud patterns.

In recent years John began experimenting with Kiley’s Exo Skin and Pro Nymph Shells. Trimmed into narrow strips, Exo Skin is secured over the body in similar fashion to other narrow shellback materials such as Thin Skin or plastic bag strips. Pro Gammarus Nymph Shells are a realistically shaped plastic shell back option featuring rib marks and eyes. Available in three different sizes and colours, Gammarus Nymph Shells add an injection of realism that both trout and fly fisher find hard to resist. When using Gammarus Nymph Shells place the eyespots at the front of the hook. From time to time you see scud patterns with eyes at the rear of hook that anatomically makes no sense.

A coating of UV resin on just about any shellback material you choose provides a finishing touch of additional realism, translucency and durability.

Although not always a popular pattern choice for fly fishers, calorie-rich scuds are extremely popular with trout. Growth rates of two pounds per season are not unheard of for trout inhabiting scud-rich waters. Second in importance only to chironomids in the diet of trout in productive lakes, scud patterns should feature prominently in any stillwater fly box. John Kent’s Humped Back Spawner is an excellent candidate.

How to Tie the Humped Back Spawner Designed by John Kent

Hook: Curved Scud/Pupa, #8-#12
Rib: Small Wire, Black or 4x-6x tippet
Shellback: Pro Nymph Shell, Gammarus or Exo Skin
Body: Blend of 75% Rabbit Mixed With 25% Ice Dub
Hot Spot: Glass Bead, Orange (8/0 When Using 7/64” Metal Bead, 10/0 When Using 3/32” Metal Bead)
Head: 7/64” or 3/32” Metal Bead, Copper

Tying Note: Choose a dubbing blend to match naturals. Popular color choices include olive, grey/olive, olive/yellow and natural rabbit.

Tying Instructions:

  1. Step 1 tying instructions for the Humped Back Spawner
    Via Phil Rowley

    Slide a copper bead followed by an orange glass bead onto the hook shank. Push both beads forward to the hook eye. Attach the tying thread at the mid point of the shank. Cover the rear portion of the shank at least one third down into the hook bend. Attach the rib and shellback material at the rear of the hook.

  2. Step 2 tying instructions for the Humped Back Spawner
    Via Phil Rowley

    Dub a robust body forward to the mid point of the hook. Slide the orange glass bead back against the dubbing. Remove any excess dubbing from the tying thread. Advance the tying thread over the top of the glass bead so it hangs directly in front. Secure the glass bead in position back against the rear portion of the body.

  3. Step 3 tying instructions for the Humped Back Spawner
    Via Phil Rowley

    Dub the balance of the body forward between the orange glass bead and the rear of the metal bead. Push the metal bead up tight against the hook eye with the forward portion of the body.

  4. Step 4 tying instructions for the Humped Back Spawner
    Via Phil Rowley

    Pull the shellback over the top of the body and glass bead. Tie off the shellback behind the metal bead.

  5. Step 5 tying instructions for the Humped Back Spawner
    Via Phil Rowley

    With the shellback in place, spiral the rib forward over the shellback using evenly spaced wraps. If you are winding the rib over a Pro Nymph shellback, wind it over the corresponding rib markings. Tie off the ribbing at the rear of the metal bead. If you used a wire rib break of the excess using a pulling and twisting motion.

  6. Step 6 tying instructions for the Humped Back Spawner
    Via Phil Rowley

    Whip finish directly behind the metal bead and remove the tying thread. Coat the shellback with UV resin and cure. Give the body a final brushing to simulate the legs of a natural scud. Trim the dubbing fibers even with the bottom of the hook point.