Notes on the Anacroneuria (Plecoptera: Perlidae) of Guyana with the Description of a New Species

A new species of perlid, Anacroneuria takutu sp. n., from Guyana is described and a new record of A. arawak Stark is given. Two additional species of Anacroneuria, represented only by female specimens, are described under informal designations.     

The larval morphology and ecology of a new species of Ecnomus from lake Naivasha,Kenya (Trichoptera: Ecnomidae)

Ecnomus mennelli sp.n. from Lake Naivasha, Kenya, belongs to the natalensis‐group. E. thomasseti was also found at the lake, and these are the first records of Trichoptera from Naivasha. Adults and larvae of both species were collected, and an analysis of the gut contents of the larvae showed them to be mainly predator y on small invertebrates. The ecological requirements and distribution of the African species of Ecnomus are discussed.     

中国四节蜉属一新种(蜉蝣目：四节蜉科)

报道了采自江苏省南京紫金山麓四节蜉属一新种逸仙四节蜉Baetis yixiani sp.nov.(成虫、稚虫),该新种稚虫近似于B. laetificus,主要区别为前者腹部第1～７节有7对鳃,而后者腹部第2～７节只有6对鳃。模式标本保存于南京师范大学生物系。     

A Revision of the Limnius perrisi Subspecies Group (Coleoptera: Elmidae) in the Iberian Peninsula

A revision of the Limnius perrisi subspecies group in the Iberian Peninsula is presented. Limnius perrisi subcarinatus (Sharp, 1872) is a new synonym of Limnius perrisi carinatus (Pérez-Arcas, 1865). Morphological variability related to some elytral interstriae corresponds to a geographical gradation. Limnius perrisi is restricted to the headwaters of highslope streams with low levels of dissolved minerals.     

A new species of Acentrella Bengtsson (Ephemeroptera: Baetidae) from Great Smoky Mountains National Park,USA

Acentrella barbarae sp. n. is described from eggs, larvae, and imagines collected from Great Smoky Mountains National Park, North Carolina and Tennessee, USA. Larvae were collected from cobble-pebble substrate in stream rapids. Life stages were associated by rearing. Eggs have longitudinal chorionic ridges with small, longitudinal furrows. Larvae are distinguished by having segment 3 of the labial palp apically rounded, abdominal terga with posteromedian projections, and tibiae and tarsi with relatively short setae on the outer margins. Imagines are distinguished by the colouration and posterior elevation of abdominal terga. Other Acentrella larvae occur in the same streams as the new species, including A. parvula, which we report from Tennessee for the first time. We provide an updated key to the larvae of North American Acentrella species.     

The role of canopy cover on the recovery of periphyton and macroinvertebrate communities after a month-long flood

We studied the recovery of periphyton and macroinvertebrate communities in a second order stream after a month-long spate that began as increased discharge due to snowmelt in April 2000 but continued through May as a result of frequent rainstorms. We sampled macroinvertebrates and periphyton in June 2000 at three different sites—an upstream site in a conifer tree plantation, a second site ca. 800 m downstream in a mixed hardwood forest, and a third site ca. 1.4 km downstream where there was an open canopy. Periphyton abundance was low on 6 June at all sites but increased 10-fold at the open canopy site the following week (13 June), appearing as a thick mat of Ulothrix. By 26 June, periphyton biomass (as both chlorophyll a and ash free dry mass) had decreased by 80% whereas densities of Chironomidae increased 50-fold and Baetidae increased 4-fold at the open canopy site; little change had occurred in periphyton and macroinvertebrate communities at the forested sites from early to late June. Our results suggest that baetids and chironomids rapidly responded to the increased algal resource at the open canopy site due to their life history characteristics and high growth rates. Chironomids decreased the green mat of Ulothrix by using this alga in tube construction and both chironomids and baetids likely consumed this alga. The varied responses of the periphyton and macroinvertebrate communities at the forested versus open sites demonstrate a resistance to impacts by floods at the forested sites, whereas at the open canopy site periphyton and macroinvertebrate communities were more resilient to the flood disturbance. Handling editor: R. Bailey     

Labiobaetis species of Japan, Taiwan, and Korea, with a new synonym of L. atrebatinus (Eaton 1870) and reerection of the subspecies L. atrebatinus orientalis (Kluge 1983) (Ephemeroptera, Baetidae)

We associated nymphs of Labiobaetis sp. G and Labiobaetis sp. Q from Japan with imagoes reared from nymphs in the field. Labiobaetis sp. G was identified with L. atrebatinus (Eaton 1870) based on characters of the reared male and female imagoes, nymphs, and eggs. We also synonymized a Taiwanese species, L. morus (Chang and Yang 1994), with L. atrebatinus. After further examination of the characters of male imagoes from Japan and Korea and nymphs from Japan and Taiwan, we found them to be correspondent to subspecies L. atrebatinus orientalis (Kluge 1983). Thus, we reerected the subspecific status of L. a. orientalis, although it had been considered not distinguishable from the nominotypical subspecies L. a. atrebatinus. Labiobaetis a. orientalis is distributed in the Russian Far East, Japan, Korea, and Taiwan. We identified Labiobaetis sp. Q with L. tricolor (Tshernova 1928) based on characters of the reared male and female imagoes, nymphs, and eggs. Labiobaetis tricolor was recorded from Japan for the first time.     

Genera and species of Baetidae in Japan: <Emphasis Type="Italic">Nigrobaetis,Alainites, Labiobaetis</Emphasis>, and <Emphasis Type="Italic">Tenuibaetis</Emphasis> n. stat. (Ephemeroptera)

We describe morphological characters of the genera Nigrobaetis, Alainites, Labiobaetis, and Tenuibaetis n. stat. and provide generic situations of six Japanese species: Nigrobaetis chocoratus n. comb., N. sacishimensis n. comb., Alainites atagonis, A. florens, A. yoshinensis, and Tenuibaetis pseudofrequentus. To evaluate the polarities of the morphological characters and the monophyly of Nigrobaetis, Alainites, Labiobaetis, and Tenuibaetis, character states of these four genera were compared with the genus Cloeon as an outgroup. Labiobaetis is considered to be a monophyletic group supported by a wide paraglossa. Tenuibaetis is a monophyletic group that is distinguishable from the related genera by robust setae with a medial ridge on the dorsomedian surface of the nymphal femur. We did not find any synapomorphic characters of Nigrobaetis or Alainites. Although we tentatively treat Nigrobaetis and Alainites as distinct genera, they are considered to be paraphyletic taxa.     

THE EFFECTS OF PHYSICAL DISTURBANCE ON AFROPTILUM SUDAFRICANUM (EPHEMEROPTERA: BAETIDAE) POPULATION DENSITIES IN A KENYAN MOUNTAIN STREAM

Summary

The effects of physical disturbance on larval populations of the mayfly Afroptilum sudafricanum Lestage were examined in the Naro Morn River, Kenya. Disturbance was induced by stirring, shifting and relocating streambed substrates by hand. The method aimed to simulate natural physical disturbance. The effects of continuous disturbance were examined by sampling larval populations at minute intervals of up to 14 minutes. The effects of periodic disturbance were examined by sampling larval populations which had been disturbed at intervals of minutes (short-term), hours (medium-term) and days (long-term). About 85% of A. sudafricanum individuals was removed from the streambed within four minutes of continuous physical disturbance. There were higher densities at night than during the day. All densities on the control sites for the medium-term disturbance experiments were significantly higher than those on the disturbed sites. Most of the post-disturbance densities on the medium-term disturbance sites were significantly lower than the pre-disturbance densities (Tukey's honestly significance difference test, α=0.05). There was no distinct density pattern on the sites exposed to long-term disturbances. Sites with the same disturbance regime appeared to react differently, some having dramatic fluctuations in density. Disturbance effects on A. sudafricanum density were multi-faceted with different expressions in time and space. It is concluded that A. sudafricanum is highly mobile and is capable of recolonizing disturbed areas within six hours. Their high mobility enables them to crawl into the deeper sediment layers during floods. However, recovery time depended not only on species mobility but also on how densely the sources of recolonization were populated and the frequency of disturbance. Slight increases, strong declines and negligible disturbance effects on the density of A. sudafricanum were evident. Afroptilum sudafricanum is highly mobile and is capable of rapid recolonization. It is concluded that physical disturbance affects A. sudafricanum populations in the Naro Morn River.