Stoneflies. Isoperla grammatica

Transcription

1 Plecoptera K. A. Zasada Stoneflies Isoperla grammatica Introduction Stoneflies are a relatively small order containing about 3000 species, of which 34 have been found in the British Isles. As with the mayflies and dragonflies the nymphal stage is wholly aquatic, and they figure highly in the diet of fish. The adults are brownish coloured insects with very long antennae and usually two long tails at the hind-end. They possess two pairs of veined membranous wings of which the hind pair are slightly larger. Some species are quite large, measuring up to 50mm. or more across their wing-span, but none are particularly good fliers. A characteristic feature of the adults is the way in which the wings are folded flat over the body when at rest. The nymphs can be recognised by the 3-segmented tarsi on each leg, the possession of two cerci or tails and the absence of abdominal gills. Biology and Life History Female stoneflies usually hatch a few days after the first males, and mating takes place on the ground in May and June. The eggs are laid in water, and after hatching the nymphs can be found on the underside of stones or in dense masses of water plants, where they creep about slowly. They rarely swim, but when doing so use their legs as oars. The nymphs of the smaller species (e.g. Nemoura) live on green Algae and diatoms, as well as various soft or decomposing plant residues, while the larger ones (e.g. Perla), are voracious carnivores, detecting their invertebrate prey with numerous tactile hairs and bristles located on the long, jointed antennae. 42

2 Although most species breathe through their cuticle, several possess tracheal gills, which may be simple or branched. They are situated in bunches on various parts of the body, either on the side walls of the thoracic segments, between the tails or on the first segment (coxa) of the legs. Most British species take one year to develop from egg to adult, although the larger ones take up to three years or more. Dinocras cephalotes has been found to undergo thirty-three moults during its three year nymphal phase. The fully-grown nymphs, which are easily recognised by their black wing-pads, crawl out of the water, often under cover of darkness, and find sheltered places on the bank where they undergo their final moult. Since stoneflies undergo incomplete metamorphosis, from egg to nymph to adult, the nymphs are similar in general appearance to the adults. Certain species, which are normally fully-winged, tend to become short-winged at high altitudes. This occurrence is quite distinct from the short-wingedness of the males of many species since it involves both sexes. Angler s Names Many of the species of stonefly have been imitated in fly-fishing, so receiving popular names, although it is not always easy to fit the names to individual species. Creepers refer to the nymphs of Perlidae and larger Perlodidae; stonefiies to the adults of both species of Perlidae and presumably to the other larger species also. The Yellow Sally is the name given to Isoperla grammatica, the February Red is the female Taeniopteryx nebulosa and the Early Brown is the name applied to all species of Nemouridae. The Willow Fly is Leuctra geniculata, and the other species of Leuctra are called needleflies. Plecoptera of Sheffield The stoneflies tend to be restricted, almost exclusively, to the west and south of the District because of their preference for a highly oxygenated, running water habitat with stony substratum. They are one of the few groups to be encountered in the acidic, upland streams and rivers, and some species can be found at altitudes of up to about 500 metres. Their habitat preference, especially in this area, means that the value of this group in water quality estimation must be limited. The Sheffield District is particularly rich in stoneflies, with records existing for 23 of the 34 British species. In general, they fit the national distribution patterns well. Brachyptera risi (Morton) Recorded from only one site at Blackamoor in 1936 by J. M. Brown. This contrasts sharply with its national distribution since it is common and fairly abundant in small, stony streams and occasionally in moss in rivers. Protonemura praecox (Morton) Only two records, one from Ryecroft Glen by J. M. Brown in 1936, the other at Abbey Brook in the Survey. It is also fairly rare nationally. Protonemura meyeri (Piet.) This was the second most common stonefly recorded in the area, occurring in fast-flowing rivers and streams up to high altitudes. Amphinemura sulcicollis (Stephens) Quite common. Twenty records, all from rivers and large streams. 43

3 Stoneflies 1 Nemoura cambrica Chloroperla torrentium

4 Stoneflies 2 Leuctra inermis Leuctra hippopus

5 Nemurella picteti (Klapalek) Quite rare. A few scattered sites in the west of the District, including two still water sites at Wharncliffe Wood and Well Springs Pond, up to high altitudes. It is more common nationally, but found in similar habitats. * Nemoura cinerea (Retzius) Common locally in the cleaner waters in the north, west and south of the District. Found in both still and running water. * Nemoura avicularis Morton Fairly common in the west of the District. Of the seventeen records, sixteen were from running water, the other was from Wigtwizzle Stream where it joined Broomhead Reservoir. According to its national habitat pattern one would expect more records from lake shores. * Nemoura cambrica (Stephens) Fairly common in stony streams and rivers locally. It alsooccurred in a number of upland still water sites, which is a little unusual. Nemoura erratica Classen An upland stream species, perhaps more common locally than might be expected from its national distribution. Leuctra geniculata (Stephens) This would seem to be very rare locally, having been recorded at only one site in Ewden Beck by the Yorkshire Water Authority. It is a fairly common species nationally. * Leuctra inermis Kempny Recorded from only three sites locally, Blacka Moor, River Rivelin and Ecdesall Wood. This contrasts sharply with the national pattern, since it is considered very common and very abundant. * Leuctra hippopus (Kempny) This is the most commonly recorded species of stonefly in the area, occurring in stony rivers and streams up to high altitudes. * Leuctra nigra (Olivier) Fairly common locally. Interestingly, nymphs have been found at two still water sites in Wharncliffe Wood. * Leuctra fusca (L.) Fairly common locally but as the distribution map shows, it would appear to have an unusual distribution pattern, being restricted to the south-west of the District. Leuctra moselyi Morton Recorded from only two sites on the upper reaches of the River Sheaf. It is also rare nationally. Capnia bifrons (Newman) Only two local records, both by J. M. Brown: Limb Brook, Ecdesall Wood in 1935, and Limb Brook, Ryecroft Glen in Perlodes microcephala (Piet.) One record from J. M. Brown in 1936 for Totley Brook, the other from the Survey for Wigtwizzle Stream on the edge of Broomhead Reservoir. A common species nationally. * Diura bicaudata (L.) An upland species. Records from Broadhead Clough, Howden Clough and two from an Abbey Brook tributary. * Isoperla grammatica (Poda) A fairly common species locally, occurring in stony rivers and streams. 46

6 Dinocras cephalotes (Curtis) Recorded from only one site, a stream flowing into Moorhall Reservoir, More common nationally, it is usually found in rivers. Perla bipunctata Piet. Although common and abundant nationally there is only one record for this area at Blacka Moor by J. M. Brown in * Chloroperla torrentium (Piet.) Found at Blacka Moor, Limb Brook, Bull Clough, River Derwent and Bents Farm Stream. A very common and very abundant species nationally. Chloroperla tripunctata (Scop.) Found at Wharncliffe Wood in 1897 by G. T. Porritt and more recently by the Y.W.A. in Ewden Beck. Fairly common nationally. References Brown, J. M Late and early stoneflies in North Derbyshire. Naturalist, 110. Brown, J. M New and rare Yorkshire stoneflies. Naturalist, 330. Brown, J. M Early stoneflies in Derbyshire. Naturalist, 110. Brown, J. M Late emergence of stoneflies in North Derbyshire. Naturalist, Brown, J. M Early stoneflies in Derbyshire. Naturalist, Brown, J. M Derbyshire stoneflies. Naturalist, Hynes, H. B. N A key to the adults and nymphs of British stoneflies (Plecoptera) with notes on their ecology and distribution. 3rd edition. Sei. Publ. Freshw. Biol. Ass., 17,