Colonization and emergence of midges (Chironomidae: Diptera) in slow sand filter beds

Colonization by midges, and temporal changes in their community structure, were examined in slow sand filter beds. The replicated beds allow the development of communities to be traced from a known starting point.The filter beds (rectangular concrete containers filled with water) have a substratum of sand on which a rich coating of organic particles develops during passage of the water through the bed. The containers (ponds) are drained from time to time and the organic layer is then scraped off the sand surface. This occurs on average, once a month. The length of time the ponds were filled with water (bed run) during the present study ranged from 16 to 77 days.In long bed runs small midges with a short aquatic phase (Cricotopus sylvestris, Psectrocladius limbatellus, Tanytarsus fimbriatus) produced adults after 16–20 days; other, larger midges,e.g. Psectrocladius barbimanus and the Tanypodinae required a longer aquatic phase. Of the Tanypodinae, the smallAblabesmyia phatta, had the shortest duration of the four species found, and was much the most numerous member of this subfamily. Some Chironomini only appeared when the organic coating had developed over the sand surface. Midges of this tribe frequently failed to complete their larval development within the duration of bed runs and were thus trapped on the substratum at the time of cleaning. When ponds were drained after short bed runs the succession in community structure observed in long runs was arrested.Three small midgesC. sylvestris, P. limbatellus andT. fimbriatus, were collected in high numbers throughout the life of all beds, except towards the end of the longest runs in the study. This suggests that small size, short life cycles, and the ability to colonize clean substrata, are important characteristics for the development of primary chironomid communities in short-lived temporary habitats.     

The influence of sediment composition and leaf litter on the distribution of tubificid worms (Oligochaeta)

Summary The horizontal distribution of three species of tubificid worm (Tubifex tubifex, Limnodrilus hoffmeisteri and L. udekemianus in the sediment of a small stream was examined. Worm distribution was most strongly correlated with the distribution of leaf litter. This relationship was examined in the laboratory by means of choice chambers. It was concluded that; 1) the addition, to an inorganic substratum, of conditioned leaf material, enhanced its attractiveness to the worms; 2) a combination of silt-clay and leaf material was preferred by the worms to mixtures of leaf material and coarser inorganic substrata 3) some leaf species were more attractive to the worms than others; 4) there were differences between the worm species in their preferences for the various leaf species; 5) none of the three tubificid species was exclusively associated with its preferred leaf species; 6) worms would switch to less attractive leaf species if preferred alternatives were unavailable; 7) leaf material only attracted the worms once it had become conditioned; 8) this appeal was lost when the leaves were autoclaved; and 9) substratum choice was independent of worm size.We believe the worms were attracted to the leaves because the associated microfloras provided a concentration of bacterial food. Differences between the three tubificid species in their preferences for the various leaf species probably reduced trophic competition.     

Selective feeding by the aquatic oligochaete Tubifex tubifex (Tubificidae,Clitellata)

The particle size distribution of faecal pellets produced by the tubificid worm Tubifex tubifex in laboratory culture, was measured with a Coulter® Multisizer. The faecal material from worms cultured in a range of sediments was composed of particles with a mean diameter of less than 63 m, and only a few isolated larger particles were found by microscopic analysis. This suggests that this species actively selects the silt-clay fraction, avoiding larger sand particles. A more detailed analysis of faeces revealed that about 75%, by volume, was composed of particles with a mean diameter < 25m, and the mode was < 10m. T. tubifex fed selectively on the organic rich particles of the sediment, and this feeding was independent of particle size. Measurement of the organic content of faeces (measured as % loss on ignition) showed that they had a consistently higher organic content than the sediment, considered as whole sediments or the <63 m sieved fraction. On the basis of these results, we hypothesise that this species exhibits two levels of selectivity in its feeding behaviour. Thus selection is primarily based on particle size, avoiding the ingestion of sand particles and also, on the preferential selection of particles associated with organic material, within the fine (silt-clay) fraction of the sediment.     

Attractiveness and exploitation of decaying herbage by Drosophila in temperate woodland

Summary The Drosophila fauna of a deciduous flood plain forest rich in undergrowth near the river Isar, close to Munich, Germany, was surveyed in summer 1990. Decaying herbage baits (decay artificially induced) were set out to study the exploitation of that resource by Drosophila. Sixteen plant species belonging to several families dominant in the collecting area were tested. All attracted and produced drosophilid flies. Ten Drosophila species utilized decaying plant material as breeding sites; at least eight of the ten are polyphagous. Decaying stalks and leaves of Angelica sylvestris (Apiaceae) were examined in detail. In the case of the most frequent species of Drosophila attracted to A. sylvestris, the number of adults collected did not correlate with the number of flies emerging from the substrate. This was particularly true of D. limbata and D. phalerata. When oviposition and larval development of D. limbata and D. phalerata on A. sylvestris was tested in the laboratory, the number of offspring per female was the same in both species. The difference between these two species of the quinaria group in the exploitation of A. sylvestris in the field is therefore not due to differential suitability of the substrate.     

樟子松人工林营建对土壤颗粒组成变化的影响

植被恢复是退化生态系统的主要恢复措施,也是人类改善区域生态环境较为重要和直接的活动。目前,针对不同植被恢复方式对干旱半干旱地区土壤理化性质及生物特征开展了大量研究。然而,关于科尔沁沙地樟子松人工林营建对土壤颗粒组成变化的影响却鲜有报道。因此,以辽宁省章古台地区不同生长阶段(包括幼龄林、中龄林、成熟林和过熟林)的20块樟子松人工林样地为研究对象(以临近的7块天然草地为对照),研究了沙地樟子松人工林营建对0—100 cm土层土壤颗粒组成变化的影响。结果表明:沙质草地营建樟子松人工林后,不同土层土壤细颗粒(0.05 mm)含量均呈增加趋势,并且在0—10 cm层增加趋势明显,随土层深度增加土壤细颗粒增加量逐渐降低(除幼龄林外),但樟子松林地土壤颗粒组成仍以砂粒为主,土壤粘粒和粉粒含量极低(仅占5%左右)。随着樟子松人工林林龄的增加,土壤细颗粒变化量在0—10 cm层逐渐升高,而在10—100 cm层并无显著变化趋势。土壤细颗粒含量的变化在10—100 cm层与土壤含水量呈显著正相关,在0—10、20—40 cm和80—100 cm层与土壤全钾极显著负相关,在20—60 cm层与土壤有机碳呈显著正相关,在10—40 cm和80—100 cm层分别与土壤全磷呈显著正相关和负相关。综上所述,樟子松人工林营建可有效提高土壤细颗粒含量且在土壤表层效果明显,但短期内并不会使土壤颗粒组成发生显著变化,樟子松林改善土壤颗粒组成的同时也会使其他土壤因子发生相应的变化。     

Food items of the grey mullet Mugil cephalus in the Banc d'Arguin area (Mauritania)

The stomach and gut content of 22 Mugil cephalus from the Banc d'Arguin shallows (Mauritanian coast, West Africa) is examined. Quartz grains are the predominant material found in the stomach together with small portions of benthic diatoms and flakes, aggregates of fine-grained inorganic and organic particles. As the composition of this material is modified by a sorting procedure during feeding it is difficult to conclude, whether seagrass stands (muddy and mixed sediments with sand fraction) or sandy flats are preferred as feeding habitats. The animals studied did not or not relevantly utilize the non-diatom microphytes, though the environment of the Banc d'Arguin is rich in microbial mats (cyanobacteria), Vaucheria beds and epiphytic vegetation of seagrass leaves.     

Substratum stability associated with the riverine macrophyte Justicia americana

1. Patches of stable substratum in streams may be important refugia for benthic organisms during scouring floods. Streambed stone stability, packing and embeddedness were assessed within and adjacent to beds of the macrophyte Justicia americana in five Alabama streams. 2. The force needed to dislodge stones and embeddedness was about two times lower outside Justicia beds than within them. Significant positive correlations between stone stability and (i) degree of embeddedness, and (ii) the abundance of binding rhizomes and the presence of attached roots indicate that Justicia may physically modify the local streambed, indirectly enhancing substratum stability and reducing flow, thereby increasing sand deposition. 3. Despite higher stability (i.e. physical refugia during bed‐moving spates) within Justicia beds, the abundance of epilithic plants (moss and Podostemum ceratophyllum) and pleurocerid snails (Elimia spp.) was similar both inside and outside the macrophyte beds. Several physical characteristics within macrophyte beds, such as low light, reduced current and increased sand intrusion, may create suboptimal conditions for benthic organisms in these habitats. 4. Additional work is needed to determine if Justicia biogenically enhances substratum stability or if its presence merely reflects patches of stable substratum within the streambed. Regardless of the mechanism, there is an association between Justicia beds and streambed characteristics.     

Burrowing behavior and ecology of the crab-eating Indian snake eel Pisoodonophis boro

Synopsis The snake eel Pisoodonophis boro burrows, causing leaks in the embankments and damaging the paddy fields and salt pans near estuaries. Field observations and laboratory experiments were made to study this behavior. P. boro was burrowing to eat the fiddler crab Uca annulipes in the mud flats. The eel showed a patchy distribution within the Uca zone. Salinity and the physical nature of the deposits controlled the distribution of the eel. Eel population density was low when the estuary was completely filled with neritic waters during the summer and fresh water during the monsoon period. The region of greatest abundance contained a good mixture of sand, silt and clay. Eels were not found where medium and fine sand formed the bulk of the substratum. The laboratory experiments showed that P. boro preferred loam soil although it could invariably burrow into hard substratum like sand for protection. The eel adapted itself to the experimental substrates ranging from sand to fine clay. However, their natural distribution was determined by Uca distribution. As U. annulipes is not found either in salt pans or in paddy fields P. boro rarely occurs in these habitats.     

An investigation into some physical and biotic effects of flooding on reservoir mud previously subjected to a period of aerial exposure

A series of laboratory experiments were carried out in order to investigate the effects of selected physical and biotic processes on the substratum of a recently flooded gently sloping marginal zone of Plover Cove Reservoir, Hong Kong. The physical effects of disturbance of the sediments promoted the redistribution of organic matter, as shown by differences in the percentage of organic matter in the supernatant and residue resulting when reservoir mud was stirred. It is suggested that such a process would promote the transfer of allochthonous organic carbon from the marginal zone (the area of input of such material) to the rest of the water body. Substrate characteristics were also influenced by the activities of two species of benthic gastropod,Sinotaia quadrata andMelanoides tuberculata. These animals increased the rate of production of particles from soaked blocks of parent mud when compared with experimental treatments in the absence of snails. Additionally both species enhanced the production of aggregates from fine sediments with a particle size of less than 125 µm. The magnitudes of both processes were statistically significant. Laboratory observations showed thatM. tuberculata had a significantly faster rate of aggregate and fine particulate production thanS. quadrata and it is possible that the former species may have the capacity to modify the substrate characteristics of the newly flooded marginal zone of Plover Cove.Department of Zoology, The University of Hong Kong     

樟子松固沙林更新迹地草本植物多样性及其对土壤理化性质的影响

以科尔沁沙地南缘的彰武县章古台万亩林为研究对象,野外取样调查和实验室检测分析相结合,以樟子松固沙林采伐迹地为对照,研究不同植被恢复类型下樟子松固沙林更新迹地生境的改良效果,探讨植被重建后植物多样性及土壤理化性质的响应。结果表明:1)樟子松(Pinus sylvestris)固沙林更新迹地植被重建后,草本植物物种多样性增加,林下植物偶见种数目增多,13种草本植物在8个样地中未重复出现;2)与采伐迹地相比,不同植被重建类型土壤理化性质均有所改善,土壤容重、田间持水量、有机质、全氮、碱解氮、速效钾在彰武小钻杨(Populus xiaozhuanica)、五角枫(Acer mono)林地改良效果较好,全钾在红刺榆林(Hemiptelea davidii)地含量明显提高、山杏(Armeniaca sibirica)林地的有效磷相比采伐迹地明显提高,且均表现为上层改良效果优于下层;3)不同植被恢复类型土壤理化性质间存在显著差异,随着物种多样性的增加,土壤理化性质逐渐改善,土壤容重、田间持水量、有机质、全磷与植物多样性具有显著的相关性,土壤理化性质的与植物多样性相互作用,共同促进生态系统正向演替。研究结果为控制科尔沁沙地土壤沙化,加速该区生态系统的恢复与重建提供理论依据。     

THE ECOLOGY OF CLADOPHORA

Cladophora is found in a variety of marine and fresh-waters and provides habitat and food for numerous organisms. It may be the most ubiquitous macroalga in fresh-waters worldwide. This filamentous green alga can reach nuisance levels as a result of cultural eutrophication. Taxonomic identification of Cladophora species is difficult. Taxonomy may be clarified by the simultaneous culture of known taxa and material derived from field collections under the same sets of culture conditions. This should eliminate ecotypic variations in morphology. Cladophora is predominantly benthic and is often found in regions of unidirectional flow or periodic wave action. Its metabolism, and morphology are related to hydrodynamic conditions. Nitrogen and phosphorus are the most commonly reported limiting nutrients. Cladophora is a mid- to late successional species in freshwaters where it is grazer resistant. In marine communities, however, it is considered an early opportunist and relatively palatable to invertebrates. Cladophora is colonized by a wide variety of epiphytes and motile animals because it can offer protection from predation, food (in the form of epiphytes or Cladophora itself), or a substrate that is anchored against flow disturbance. Species interactions that occur within Cladophora communities include 1) competition with other primary producers, 2) top-down control of biomass, 3) association with nitrogen-fixing epiphytes, 4) grazing on epiphytes by invertebrates, and 5) complicated foodwebs in marine intertidal and freshwater communities. Because Cladophora is found in many different habitats, its ecology varies significantly with locale.     

The distribution and habitat preference of ostracods (Crustacea: Ostracoda) in a coastal sand-dune lake, Loch of Strathbeg, north-east Scotland

SUMMARY. 1. Ostracods were a numerically abundant component of the benthos >0.1 mm in size (up to 20% of the total) in the Loch of Strathbeg.
2. Distinct assemblages of species were associated with some habitats: Cypridopsis vidua (Müller) and Herpetocypris reptans (Baird) with Eleocharis palustris (L.) beds; Cypria uphtalmica (Jurine), Candona Candida Müller and Cypria exsculpta (Fischer) with Phragmites communis Trin. beds; and Limnocythere inopinata (Baird) with open sand. In contrast, no distinct ostracod assemblage was associated with submerged beds of Chara aspera Detharding, or Myriophyllum spicatum (L.).
3. The number of ostracod species and ostracod diversity increased from open sand through macroalgal and submerged macrophytes to emergent macrophyte habitats and was associated with increasing number of types of detritus.
4. Laboratory experiments suggested that substratum particle size played a dominant role in determining the distribution of L. inopinata. This species preferred sandy sediments. The distributions of both H. reptans and C. vidua were affected by food supply and H. reptans also preferred fine-grained sediments. The absence of these taxa from some habitats where food supply and sediment particle size conditions were suitable suggested that unmeasured factors played a role. A possible predatory exclusion of H. reptans from such habitats was indicated by a negative association of this species with a predatory mite.     

Ontogenetic and seasonal feeding habits of the annular seabream (Diplodus annularis L.) in Zostera sp. beds, eastern Adriatic Sea

The ontogenetic and seasonal feeding habits of 489 individuals of Diplodus annularis L. in Zostera sp. beds were studied using frequency of occurrence, numeric percentage, percentage by weight and an index of relative importance (IRI). The Schoener overlap index was used to compare diets by fish size and seasons. Diet composition including 18 different prey taxa was evidently heterogenous among annular seabream size groups, with no significant dietary overlap. In relation to body size, juveniles were omnivorous and preferred algae and plants, while adults were omnivorous and preferred animals. Principal prey items by decreasing importance were Chlorophyta (dominant taxa Cladophora sp. and Enteromorpha flexuosa), Decapoda (dominant species Upogebia pusilla), Gastropoda (important species Rissoa ventricosa and Alvania sp.), Bivalvia and Spermatophyta, as well as other food items (mostly unidentified Crustacea and fish eggs). Differences in diets among seasons were not significant.     

The influence of water and sediment properties on the occurrence of Potamocaris Dussart, 1979 (Harpacticoida) in the upper Paraná River (Brazil)

In the main channel of the Upper Paraná River, four sampling sites were established according to the profile of the bottom. Samples were carried out monthly from July 1993 to February 1995 with a modified Petersen grab. Four species were found at four sites: Potamocaris bifida, P. bidens, P. bidentata and P. tridentata. Canonical correspondence analysis indicated differences in the preferred microhabitats of the Potamocaris species, mainly in regard to sand particle size in the main river channel. Bedform stability was the most important factor affecting the abundance of this community.     

Internal structure and paleoecology of the lower Permian Uzunbulak reef complex of the Tarim Basin,Northwest China

Summary The internal construction and biotic communities of the Uzunbulak reef of the northwestern Tarim Basin are studied for the first time. The reef was built during the Sakmarian, while the reef substrate and capping beds are of latest Asselian and earliest Artinskian ages, respectively. The reef substrate beds are composed of skeletal and oncoid grainstone. Those fusulinid-dominated skeletal shoals and oncoid banks indicate a high-energy environment and produced local topographic highs on which the reef grew. Reef framework consists mainly of calcisponge bafflestone, calcisponge-Thartharella framestone, and Tubiphytes, Archaeolithoporella and Girvanella boundstones. Calcisponges were the primary frameconstructors that baffled high-energy currents. Archaeolithoporella, Tubiphytes, Girvanella and possibly microbes acted as the primary binders for the boundstone framework. Fusulinids and brachiopods were common reef dwellers. The interreef facies sediments are composed of skeletal-crinoid wackestone-packstone. Most of bioclasts have thick, micritized envelopes. The back-reef facies deposits consist of alternating skeletal packstone to wackestone and black shale. Sea-level fluctuations were probably accountable for the reef growth and demise. Of the reefal dwellers, brachiopods are extraordinarily abundant in Uzunbulak. They are assignable to five distinctive associations, one each from the reef substrate, framework and inter-reef facies, respectively, and two from the reef capping facies. The brachiopods in the substrate beds were mostly attached to hard substrates by a pedicle, while a few species rested on soft substrates by support of halteroid spines. Cementation of the ventral valve on hard substrates characterizes attachment of the reef framework brachiopods. All inter-reef species were anchored into the substratum comprising hard material by a strong pedicle. Back-reef brachiopods dominantly rested on the soft substrates by support of halteroid spines. the framework brachiopods had the strongest wave-resistant capability;those from both substrate and inter-reef facies were moderately capable of withstanding agitation; and the backreef species preferred to live in calmwater, organic-rich muddy environments.     

Colonization routes of Pinus sylvestris inferred from distribution of mitochondrial DNA variation

Understanding the present-day distribution of molecular variation requires knowledge about the history of the species. Past colonization routes and locations of refugia of Scots pine (Pinus sylvestris) were inferred from variation in mitochondrial DNA in material collected from 37 populations located in countries within, and immediately adjacent to the continent of Europe. Two mitochondrial regions, nad1 intron (exon B/C) and nad7 intron 1, were included in the study. Differentiation in maternally inherited mitochondria was high (G _ST′ = 0.824). Two new haplotypes were found at the nad7 intron 1. The occurrence of a 5-bp indel variant was restricted to the Turkish Kalabak population and a 32 bp only found in Central, Eastern, and Northern Europe. The complete absence of the 32-bp indel from the Mediterranean peninsulas supports the view that coniferous forests existed outside these areas during the last glacial maximum, and these populations contributed to the subsequent colonization of the northern parts of Europe. P. sylvestris shares features of its glacial and postglacial history with two other northern, cold-tolerant tree species, Picea abies and Betula sp. These three species differ from many other European trees for which pollen core and molecular evidence indicate colonization from southern refugia after the last glacial period.     

Periodic movement,recruitment and size-related distribution of the sea cucumber Holothuria scabra in Solomon Islands

Field studies of the sea cucumber Holothuria scabra conducted in Kogu Veke, Solomon Islands, showed monthly recruitment of newly-settled juveniles on seagrass and indicated that size distribution was a function of substratum type and depth. Adults >250 mm body length were found mainly on sand, with <5% organic matter (OM), at depths of >1–3 m. Individuals >10–250 mm were found mostly in 30–120 cm of water, on mud and muddy sand with OM content between 5 and 10%. Specimens >40–150 mm were also found in the intertidal zone, sometimes burrowed on exposed sandflats at low tide. Holothuria scabra avoided substrata of fine silt or shell and coral pebbles, and sediment with an organic content 30%. Juveniles 100 mm burrowed at sunrise and surfaced at sunset, whereas individuals >100 mm burrowed and surfaced a few hours earlier. Holothuria scabra tended to burrow when salinity decreased, whereas increased water temperatures reduced normal burrowing behaviour. Spatial distribution, observed during tank experiments, suggested that adult H. scabra aggregated prior to spawning and in response to the lunar cycle. The formation of pairs, trios or larger groups increased during the new moon and was most common just before the full moon. Newly-settled juveniles up to ca. 9 mm were found on seagrass leaves. Typically, maximum densities and smallest recruits were observed a couple of weeks after the full moon, lower densities and slightly larger recruits were found a few days later. Juveniles with a mean length around 65 mm released on sand moved less and grew faster than juveniles released in seagrass beds or on substrata of shells and crushed coral.     

我国北方岩溶泉域刚毛藻的系统发育及形态学研究

脆弱刚毛藻(Cladophora fracta)是一种大型丝状绿藻,生境分布广泛。然而,对于岩溶泉域分布的刚毛藻研究较少,它们的遗传多样性、生物地理亲缘性和生理特性都有待于深入研究。该研究对我国北方地区五个典型岩溶泉域的50个脆弱刚毛藻样本进行了形态学和分子系统学描述。主要研究目标:(1)对我国北方地区五个典型岩溶泉的刚毛藻生境进行描述;(2)根据形态学特征和分子序列对藻体进行鉴定;(3)探究生境对藻体生理特性的影响。结果表明:基于SSU和LSU序列的结果,发现所分析的50株刚毛藻个体为同一种,同时还发现了13个不同的核糖体基因型。基于SSU和LSU的系统发育树,刚毛藻属均未能形成单系分支,分布在三个不同的分支上。13个样本基因型在SSU和LSU树中的位置相似,与Cladophora vagabunda有很高的序列同源性,但是形态特征却差异很大。从显微结构结果来看,五个岩溶泉域采集到的刚毛藻在细胞直径上无显著差异,藻体的形态特征与脆弱刚毛藻相一致。但是,岩溶泉域采集的藻体细胞直径比文献报道中在湖泊和河流中采集的脆弱刚毛藻直径要大。另外,仅在两个地点(XA和ST)采集的标本中发现有假根状分枝。因此,基于形态学和分子序列的结果,将这五个泉域的刚毛藻鉴定为脆弱刚毛藻(Cladophora fracta)。     

Lack of evidence on hybrid swarm in the sympatric population of Pinus mugo and P. sylvestris

Natural hybridisation between the taxa from Pinus mugo complex and P. sylvestris was postulated in several sympatric populations of the species in Europe. However, due to the absence of precise methods for identification of hybrid seeds and hybrid trees, the frequency of hybridisation and its influence on the genetic structure of relict P. mugo populations has not been clarified so far. In the present study, the species-specific chloroplast DNA (cpDNA) marker and isozymes were applied to test the hybridisation hypothesis in a postulated hybrid swarm population of the species from “Bór na Czerwonem” reserve at the northern foothills of Tatra Mts., Poland. The cpDNA marker was used to identify hybrids within two groups of polycormic (multi-stemmed) and monocormic (single-stemmed) pines from this population. Allelic frequencies at isozyme loci from both groups were compared to frequencies found in allopatric populations of the species. Additionally, cpDNA haplotypes of seedlings derived from open pollinated seeds were studied to detect the possibility of successful cross-pollination. The mixture of seedlings with P. sylvestris and P. mugo cpDNA haplotypes was derived from one parental tree that indicates hybridisation. However, all the mature polycormic pines had cpDNA haplotypes species specific to P. mugo and the isozyme frequencies were similar to frequencies found in three allopatric populations of P. mugo from Tatra Mts. (mean genetic distance, Dn=.027). The differences were much larger in comparisons with monocormic pines from this area (Dn=.085) and two P. sylvestris samples from distant allopatric populations (Dn=.077). Nearly all monocormic pines had cpDNA species specific to P. sylvestris and isozyme frequencies similar to other populations of this species (mean Dn=.004). Only one P. sylvestris-like monocormic tree had cpDNA of P. mugo and can be considered as a hybrid. The results do not provide evidence supporting the hybrid swarm hypothesis. Rather, the results suggest that mature hybrids have a low frequency within this population and (rare) hybridisation is not reciprocal but unidirectional with P. mugo as pollen donor.     

Life cycle of Hydrobaenus kondoi Sæther (Chironomidae) at the middle reaches of the Kiso River, Japan

The life cycle and biological characteristics of the nuisance midge, Hydrobaenus kondoi Sæther were studied in 1989–90 at the middle reaches of the Kiso River, Japan. A study of seasonal abundance of both adults and larvae revealed that the Kiso River population was bivoltine. In laboratory cultures, the species required 840.7 degree-days to complete the life cycle. Larvae built a cocoon in the second instar for aestivation during the high temperatures of summer. The cocoons were found attached to sand grains in shallow water near shore.