Lockdown Day 3

Covid Lockdown Day Three


It is all very well tying flies and fishing flies but what are we trying to imitate when we do so?

Having a basic understanding of entomology and the insects, both aquatic and terrestrial which fish feed on will help with both fly tying and fishing.

Today I thought we would take a step back and look at some basic entomology (the study of insects)..  You don’t need to be an expert and you don’t need to use Latin names but it does benefit both angler and fly tyer to have some knowledge of the bugs out there that fish eat.

Not only does that add a level of interest when seeing insects out on the water, but it will also help a great deal in terms of fly proportions when you are tying.

The basic categories of imitative flies used by trout anglers specifically would encompass most of the following:

Nymphs: Imitating the juvenile subsurface forms of Mayflies, Dragonflies, Damselflies and the like, Insects which undergo something called incomplete metamorphosis, more of that later.


Note that there is considerable variation of different mayfly nymphs; some are designed to hold on in fast water, some swim and some burrow under the sand or silt. But they all have the same basic layout and same parts.

Larvae: Imitating the larval forms of insects which undergo complete metamorphosis, Sedges (Caddis Flies) and midges, the larvae transform into Pupae before hatching and the Pupae then transform into the adult.

Again there is considerable variation amongst different larvae,  Midge larvae although commonly red are also sometimes green , caddis larvae of different species may build houses from sand or stone or only build nets with which they catch food. The basic structures are however all pretty similar.

Pupae: Imitating the pre-emergent forms of Sedges (Caddis Flies) and Midges for example, insects which undergo Complete Metamorphosis.

Midge and Caddis pupae are of most interest to anglers during a hatch, the ascending pupa are targeted deliberately by feeding fish.

Emergers: Imitations of various aquatic insects in the process of emerging and drifting towards or indeed at the surface. These can be imitations of either Nymphs or Pupae.

Stillborns or cripples: It has been long recognized that fish will, at least on occasion, target those insects which fail to hatch properly and become stuck in the shuck or surface film. These flies are designed to imitate such failures and for some reason generally refer to Mayflies so unfortunately afflicted rather than caddis or midge patterns, although one presumes that they can also get “stuck” but that is another story.

Duns or Sub Imagos: Flies imitating the first stage of adulthood of mayflies when newly hatched, they are not as bright or as shiny as the spinners.

Spinners or Imagos: Flies imitating the moulted and fully formed adults of mayfly species either returned to lay eggs or dead on the water after mating. Frequently more shiny with glassine wings. When dead on the surface they frequently lie in a “crucifix” position, wings outstretched.

Note: Mayfly species come in a wide variety of sizes and colours but again the essential body parts and layouts are much the same. (That means as a fly tyer you can use the same basic pattern to tie a wide variety of imitations to cover most mayflies just by changing colours and sizes)

Adults: Caddis flies, midges, and damselflies for example don’t have sub imago and imago stages and emerge as fully formed adults, therefore imitations of those would normally simply be referred to as adults.

Terrestrials: Flies that imitate non aquatic insects which find themselves in the drink as it were. Crickets, Grasshoppers, Cicadas, Ants and Beetles all fall into this category. Most terrestrial patterns are dry flies and designed to float but you can also fish with good effect sunken beetles and ants so there are no hard and fast rules.

A note on Mayflies:

Throughout this book I refer to mayflies in the American sense, that is to say up-winged aquatic insects of the order Ephemeroptera . In the UK in particular the term mayfly is restricted to describing one or two large mayflies that supposedly hatch in May but are more likely encountered in June, primarily Ephemera Danica. The other British Mayflies tend to be referred to in terms of specific names such as Iron Blue, Pale Watery etc. In the US the mayflies also have specific names such as Pale Morning Dun, but are still collectively referred to as “Mayflies”. It can all be a bit confusing but generally the American way of speaking, referring to them all as Mayflies is probably becoming more in vogue, it is just that most of them don’t hatch in May either.


Understanding metamorphosis:


Aquatic insects undergo one of two types of metamorphosis either Complete or Incomplete. As mentioned previously, Midges and Sedges (Caddis Flies) undergo complete metamorphosis. That is they go through the following developmental stages.





Mayflies, Dragonflies and Damselflies undergo Incomplete metamorphosis. That is they go through the following developmental stages.

Egg……nymph……..sub adult……..adult.

Mayfly sub adults are called sub imagos, Dragonfly sub-adults are called tenerals

The main difference from an angling perspective is that insects undergoing complete metamorphosis have a pupal stage whilst those who go through incomplete metamorphosis have nymphal stages. It would therefore be wrong to call a fly “John’s Caddis Nymph” or “Sue’s mayfly pupae”. For the record nymphs do go through stages where they simply become bigger nymphs these stages are called “instars”.



Being able to recognize basic insect forms will not only help you with your fishing but equally with tying the right flies for the conditions and recognizing which ones to use when on the water. You may find flies on the water, in the air, bankside vegetation or better still in the trout’s stomach, the latter being a pretty sure indication of predation on which you can hang your piscatorial hat.

It isn’t possible to show all the variations but the main groups can at least be recognized from the following chart.





Sometimes it is simple to recognize what trout are eating if you can see the flies on the surface, subsurface insects however account for more feeding on the part of the fish. You may see the insects or trap them in a net if you go looking for them . More likely you will be able to identify them from the stomach contents of trout already caught. These are the primary forms that you are likely to encounter.


Having some knowledge of basic entomology can be fun and interesting, it will help you identify different food forms when on the water and equally assist in proportions when you are tying flies.


You don’t need to get into the minute details ,small black caddis or size 16 Olive Dun will probably be more than enough to allow you to fool some trout with your imitations.


Flytying challenge for the day:


The Deadly Damsel.. a damselfly nymph imitation primarily for use in Stillwater lakes and dams.

You may be fortunate enough to be on the water during a damsel fly migration, but even if you are not these bugs take a year to mature, so the chances are there are always some around.

If you have nothing better to base your fly selection on than that it is a good start. Trout in stillwaters will generally be pretty opportunistic and a damselfly nymph is a pretty safe bet if you have no other indication as to what the fish might be eating. As previously there are both graphic and video instructions for tying this pattern below:


Key points:

Damselfly nymphs are very mobile, they wiggle when they swim, they are also much thinner than most commercial patterns would have us believe.

Key triggers are pronounced eyes, “hammer-head” shape head,  long thin abdomen, small wing cases and fairly prominent legs which are held outwards when the nymph is swimming.

Most damselfly nymphs are olive green but they do come in other colours. When tying aim for a really thin body. The marabou tail doesn’t need to be overly thick to provide some “wiggle” when in the water.


I hope you are all getting some benefit from these posts, do leave a comment, recommendation, suggestion or query. It keeps me motivated.

If you are keen to push on and not to wait for the various instructions coming you can download the books on line and benefit from a 50% discount. The links and discount codes are shown below:

Discount code Essential Fly Tying Techniques: DR62J Code will expire 17 April 2020

Discount code Guide Flies : SB94S Code will expire 17 April 2020



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3 Responses to “Lockdown Day 3”

  1. Jeff Davies Says:

    As a newbie to fly tying, I am really enjoying these daily posts. These digestible bits of info are great. Lots of great tips and tricks to learn and master. Thank you.

  2. Mark Dell Says:

    Great effort, Tim! Thank you.

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