Flylife on the River Teifi

Mayfly (male)

During 1995 and 1996, Melvin Grey and Pat O'Reilly carried out a survey of the water life of the River Teifi as part of the research for a new book, Matching the Hatch, first published in 1997 (and with sales now exceeding 25,000 copies). The results are surprising: they were able to identify several species not generally thought to occur this far west. In fact, the flylife of the Teifi is considerably more varied than that which they found in the rich chalk streams of southern England.

Members who fish for trout on the River Teifi may find this summary of their findings useful when working out which natural flies they need their artificial patterns to copy. (The fly shown on the left is a male Mayfly, Ephemera danica; it is somewhat smaller and noticeably darker than the female.)

Upwinged flies - Ephemeroptera

Common name

Scientific genera and species

Peak time

Abundance

Mayfly Ephemera danica Spring moderate
Olive upright Rithrogena semicolorata Spring high
March brown Rithrogena germanica Spring moderate
Autumn dun Ecdyonurus dispar Autumn moderate
Large brook dun Ecdyonurus torrentis Spring moderate
Large green dun Ecdyonurus insignis Summer  low
Yellow may Heptagenia sulphurea Spring high
Dusky yellowstreak Heptagenia lateralis Summer moderate
Purple dun Paraleptophlebia cincta Summer low
Turkey brown Paraleptophlebia submarginata Spring very low
Blue-winged olive Ephemerella ignita Summer high
Large dark olive Baetis rhodani Spring moderate
Medium olive Baetis vernus; Baetis tenax Summer high
Small dark olive Baetis scambus Summer high
Iron blue Baetis muticus Summer high
Pale watery Baetis fuscatus Summer high
Pale evening dun Procloeon bifidum Summer moderate
Small spurwing Centroptilum luteolum Summer high
Large spurwing Centroptilum pennulatum Summer moderate
Caenis fly Caenis and Brachycercus species Summer high
Two rather surprising omissions are the late march brown, Ecdyonurus venosus, which is generally common on spate rivers, and the sepia dun, Leptophlebia marginata, which is found in some North Wales rivers. It would be good to hear from any members who have positively identified these species. The yellow evening dun, Ephemerella notata, doesn't feature in the list; anyone seen this fly on the Teifi?
 

Sedge flies - Trichoptera

Only a small selection of the sedges, stoneflies, midges and other flies was included in the survey, but again the findings may prove useful to trout fishers on the Teifi.

Common name

Scientific genera and species

Peak time

Abundance

Grannom Brachycentrus subnubilus Spring high
Brown sedge Anabolia nervosa Autumn moderate
Brown silverhorn sedge Athripsodes albifrons Summer high
Caperer Halesus radiatus Autumn moderate
Sand fly Rhyacophila dorsalis Summer moderate
Cinnamon sedge Limnephilus lunatus Spring moderate
Large cinnamon sedge Potamophylax latipennis Summer high
Grouse wing Mystacides longicornis Summer moderate
Welshman's button Sericostoma personatum Summer high
Marbled sedge Hydropsyche instabilis Summer low
Black sedge Silo nigricornis Summer high
Yellow spotted sedge Philopotamus montanus Spring moderate
Black silverhorn Mystacides nigra Summer high
 

Stoneflies - Plecoptera

Common name

Scientific genera and species

Peak time

Abundance

February red Brachyptera risi Spring low
Large stonefly Perlodes microcephala Spring moderate
Small yellow sally Chloroperla torrentium Summer high
Yellow sally Isoperla grammatica Summer high
Needle fly Leuctra fusca Autumn high
Small brown Nemoura cinerea Summer low
 

True flies - Diptera

Common name

Scientific genera and species

Peak time

Abundance

Black gnat Bibio johannis Spring moderate
Hawthorn fly Bibio marci Spring high
Medium craneflies Tipulidae Summer high
Daddy-long-legs Tipula maxima Autumn high
Reed smuts Simulium species Summer moderate
Large green midge Chironomus plumosus Summer high
The heather fly was a conspicuous absentee during the survey, but it is sometimes seen in summer the Teifi Valley.