What is on the water, month by month

1. Large Dark Olive Baetis rhodani Midday, best on cold grey days. Try: Adams or CDC F-Fly, size 14–16. main hatch
2. Needle fly Leuctra fusca Mild autumn afternoons. Try: Partridge & Orange, size 16. main hatch
3. Iron Blue Baetis niger Cold, blustery days. Try: Dark CDC F-Fly, size 16–18. some about
4. Blue-winged Olive Serratella ignita Evening; spinner falls at dusk. Try: Parachute Adams, size 16; Rusty Spinner. some about
5. Sedges Trichoptera Dusk and into dark. Try: Elk Hair Caddis or Klinkhåmer, size 12–14. some about
6. Grasshoppers Acrididae Windy afternoons beside meadows. Try: Dave’s Hopper, size 10. some about
7. Crane flies Tipulidae Breezy days, late summer into autumn. Try: Daddy Long Legs, size 10. some about
8. Midges Chironomidae All day; warmest hour in winter. Try: Zebra Midge or Griffith’s Gnat, size 20. some about
9. Freshwater shrimp Gammarus pulex Always on the riverbed. Try: Sawyer’s Killer Bug, size 14. some about

• Large Dark Olive Baetis rhodani

  A sturdy upwinged fly about 9 mm long with two tails. Dull grey wings held upright, body a dark olive-brown, paler underneath. The tiny hindwing is easy to miss. On a cold day the duns ride the water for a long way before they can fly.

  Mayfly · Hook 14–16 Match it with the Adams.

• March Brown Rhithrogena germanica

  A big, handsome fly of 12–14 mm with two tails and mottled fawn-and-brown wings that show a pale, clear patch in the middle. The body is dull brown with straw-coloured rings. The flat, stone-clinging nymph has broad gill plates.

  Mayfly · Hook 12 Match it with the Partridge & Orange.

• Early stoneflies Taeniopteryx, Protonemura

  Slender brown flies 8–12 mm long that fold their wings flat or rolled along the back, giving a narrow, stick-like outline. Two short tails, long antennae. They run about on bankside stones and fence posts and fly weakly.

  Stonefly · Hook 14–16 Match it with the Snipe & Purple.

• Grannom Brachycentrus subnubilus

  A small grey-fawn sedge about 10 mm long with roof-shaped wings. Females carry a bright green ball of eggs at the tip of the abdomen, which is the surest way to know them. Swarms drift over the water like smoke.

  Caddis · Hook 14 Match it with the Elk Hair Caddis.

• Hawthorn fly Bibio marci

  A jet-black, hairy land fly about 12 mm long that flies slowly with its long hind legs trailing beneath it like an undercarriage. Clear wings with a dark front edge. Unmistakable once you have seen the dangling legs.

  Terrestrial · Hook 12 Match it with the Hawthorn Fly.

• Iron Blue Baetis niger

  Small and very dark: 6 mm long with inky blue-black wings and a dark brown-olive body, two tails. Among other olives it looks like a fleck of soot. The male spinner, the “jenny spinner”, has a translucent white body tipped with red-brown.

  Mayfly · Hook 16–18 Match it with the CDC F-Fly.

• Mayfly Ephemera danica

  The largest upwinged fly of all: body up to 20 mm, three long tails, cream abdomen with dark brown blotches and heavily veined grey-green wings. The spinner has glassy wings and a chalk-white body, and dies spread-eagled on the water.

  Mayfly · Hook 8–10 long shank Match it with the Grey Wulff.

• Yellow May Dun Heptagenia sulphurea

  No other river fly is this colour: wings and body a clear sulphur yellow, with two tails and, in the dun, blue-black eyes. About 10 mm long. Hatches are a trickle rather than a flush.

  Mayfly · Hook 14 Match it with the CDC F-Fly.

• Medium Olive Baetis vernus

  The standard summer olive: 7–8 mm, two tails, medium-grey wings and a body of brownish olive that looks paler and yellower than the large dark olive of spring. If in doubt on a summer morning, it is probably this.

  Mayfly · Hook 16 Match it with the Greenwell’s Glory.

• Pale Watery Baetis fuscatus

  A small, pale fly of 6 mm with two tails, very light grey wings and a watery pale-olive body. The male dun has lemon-yellow eyes. In the air it looks almost white against dark trees.

  Mayfly · Hook 16–18 Match it with the CDC F-Fly.

• Blue-winged Olive Serratella ignita

  The only common olive with three tails. Wings dark blue-grey and noticeably tall, body olive-green turning rusty in the female. The egg-laying female is the “sherry spinner”, and carries a green ball of eggs under her tail.

  Mayfly · Hook 14–16 Match it with the Parachute Adams.

• Sedges Trichoptera

  Moth-like flies with four hairy wings folded in a tent over the body and long antennae pointing forward. No tails. Colours run from pale cinnamon to dark brown, sizes from 8 to 25 mm. They flutter rather than drift.

  Caddis · Hook 10–16 Match it with the Elk Hair Caddis.

• Black gnat Bibio johannis

  A catch-all name for several small black land flies of 4–6 mm with shining, flat-folded wings. They look like thin houseflies. Mating pairs often fall on the water together.

  Terrestrial · Hook 16–20 Match it with the Black Gnat.

• Ants Lasius niger

  Three distinct body sections with a narrow waist, elbowed antennae; winged ants carry two pairs of clear wings longer than the body. Black or dark red-brown, 4–8 mm.

  Terrestrial · Hook 14–18 Match it with the Foam Ant.

• Grasshoppers Acrididae

  Stout green or brown insects of 15–25 mm with large jumping hind legs and short antennae. On the water they kick hard and sit half-drowned, body awash.

  Terrestrial · Hook 8–12 Match it with the Dave’s Hopper.

• Crane flies Tipulidae

  The daddy long legs: a thin grey-brown body of 15–25 mm, two narrow wings and six absurdly long, fragile legs that trail behind in flight. Clumsy fliers that are easily blown about.

  Terrestrial · Hook 10 long shank Match it with the Daddy Long Legs.

• Needle fly Leuctra fusca

  The thinnest of the stoneflies: a dark brown fly 6–9 mm long whose wings wrap tightly round the body, so that at rest it looks like a short dark needle. Runs quickly over stones.

  Stonefly · Hook 16–18 Match it with the Partridge & Orange.

• Midges Chironomidae

  Non-biting, mosquito-like flies with a slim body, wings shorter than the abdomen and, in males, feathery antennae. The pupa is a small curved comma with white breathing tufts at the head. Black, olive, red or grey.

  Midge · Hook 18–24 Match it with the Zebra Midge.

• Freshwater shrimp Gammarus pulex

  A curved, flattened crustacean 10–18 mm long, grey-olive to pale tan, that swims on its side in short darts. Many legs, no wings at any stage. Some carry an orange spot, which is why pink and orange imitations work.

  Crustacean · Hook 12–16 Match it with the Sawyer’s Killer Bug.

Find these patterns in the fly box