The Ephemeroptera, Plecoptera and Trichoptera caught by emergence traps in two streams during 1958

Abstract

1. The captures from emergence traps in a high mountain stream, Whelpside Ghyll, are compared with those from similar traps in a warmer lower stream, Ford Wood Beck. 2. The number of species caught by the Ford Wood Beck traps and the number of species known to inhabit the stream are discussed. 3. In Whelpside Ghyll the traps yielded 4 species of Ephemeroptera, 12 of Plecoptera and 7 of Trichoptera, in Ford Wood Beck, 6 species of Ephemeroptera, 8 of Plecoptera and 7 of Trichoptera. 4. Leuctra hippopus, L. inermis, Chloroperla torrentium, Isoperla grammatica, Baetis rhodani, B. pumilus and Philopotamus montanus were caught from both streams. 5. Species found in Whelpside Ghyll and not in Ford Wood Beck are Ameletus inopinatus, Baetis tenax, Protonemura montana, Diura bicaudata and Capnia vidua, of which two are known high-altitude species and one, possibly two, is known also from stony lake shores being kept out of other habitats presumably by competition. 6. The proportion of Baetids to Ecdyonurids and Ephemerellids is higher in the Whelpside Ghyll station than in streams at lower altitudes. 7. There was, in both streams, a succession of Protonemura and Leuctra species but the Leuctra species, except L. fusca, were not isolated in time. 8. The distribution of the sexes during the emergence period of 6 species of Plecoptera is shown. 9. There was a considerable difference in the emergence period from the two streams of Leuctra hippopus, L. inermis and Chloroperla torrentium, the emergence period in Ford Wood Beck being earlier and shorter than in Whelpside Ghyll. 10. Leuctra inermis has emerged from Ford Wood Beck during six successive years in May and June with only about 14 days difference between first emergers, and Chloroperla torrentium, emerging during May, June and July, has had only about 19 days difference between first emergers during that time.