Emergence of blackflies (Diptera: Simuliidae) from a small forested stream in Ontario

Three species of blackflies were found in emergence-trap samples taken overa period of 8 months from a second-order, forested, cold-stenothermal stream in southern Ontario. The emergence phenologies of the two common species, Prosimulium mixtum and Stegopterna mutata, are described and compared with their phenologies in other streams in North America. Hypotheses are presented for the poor faunal diversity and prolonged emergence of the two species in the stream studied. Emergence data are used to describe the pupal distribution in the stream.Wing-length measurements showed a distinct dimorphism in P. mixtum: females were larger than males. Adult size (except of P. mixtum females) varied among sampling sites in the stream and, in the case of S. mutata, this variation was time dependent.     

Emergence and Composition of Trichoptera from Karst Habitats,Plitvice Lakes Region,Croatia

Adult Trichoptera were observed at the Plitvice Lakes, Croatia during two years (2000 and 2001) using pyramid‐type emergence traps. A total of 1350 individuals and 37 species were collected. Throughout the study, the emergence patterns showed only minor variations regarding differences in particular habitats. During 2000 most species emerged in June, and in 2001 in May. The complete emergence period is shown for all collected species and studied in detail for abundant species. Excluding Allogamus uncatus, all abundant species emerged in summer, with most exhibiting a long emergence period. Rhyacophila fasciata had the longest emergence period in both years of the study and also showed winter activity. Trichopteran diversity and equitability were calculated and trophic relationships of the collected species were identified for each sampling site in order to obtain better insight into trichopteran community structure. Results indicated that the trichopteran community could be grouped according to travertine barriers and stream habitat types. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Die Trichoptera-Emergenz im Mittellauf eines Bergbaches des Thüringer Waldes (Insecta,Trichoptera)

Fifty-seven species of caddisflies were identified in samples taken over a 7-month period from a large emergence trap placed on the mid-reach of a forested mountain stream in the Thuringian Forest, East Germany, in 1984. A total of 4,673 specimens were obtained during the sampling period. The community was dominated by collectors and shredders (52 % and 35.6 % of biomass) indicating a high input of allochthonous organic material from the bank trees as well as from upper stretches of the stream. The emergence periods and patterns of the common species are described and compared. Some species showed significant departures from a balanced sex-ratio. An explanation is proposed to account for the general unpredictability of sex-ratios in emergence traps. Unusual emergence patterns of 5 species are discussed in detail.     

New records of polycentropodid caddisflies from Korea (Insecta: Trichoptera)

Four species of the family Polycentropodidae –Plectrocnemia baculifera, P. kusnezovi, Paranyctiophylax hjangsanchonus and Polyplectropus nocturnus– are recorded from Korea. Polyplectropus nocturnus is newly recorded from the Korean peninsula. The other three species are recorded from the Republic of Korea for the first time.     

Observations on the distribution of some chironomids (Diptera) and caddisflies (Trichoptera) in the Killarney area,Ireland

The Killarney region, south-west Ireland, has a mild oceanic climate, yet elements of the flora and fauna in the area appear to have disjunct distributions. Eleven chironomid and two trichopteran taxa, which are considered cold stenothermous and generally occur outside Ireland at high altitudes or northern latitudes, are found in waters around 25 metres above sea level in Killarney. These are believed to be glacial relict elements which have survived in the region to live with a fauna depauperate in comparison to western Europe.     

Ten polymorphic microsatellite loci isolated from the alpine caddisfly Allogamus uncatus Brauer (Trichoptera: Limnephilidae)

Here we report the development of 10 microsatellite loci for the alpine caddisfly, Allogamus uncatus. Polymorphism as detected in 24 individuals ranged from three to 17 alleles per locus, and observed heterozygosity ranged from 0.087 to 0.864. These primers will enable research on the genetic population structure of this species, the extent of gene flow among alpine permanent and temporary streams, and the genetic consequences of extinction/recolonization events.     

Species assemblages and community structure of adult caddisflies along a headwater stream in southeastern Ghana (Insecta: Trichoptera)

Adult caddisflies were collected at 12 sites along a 5 km stretch of a forested headwater stream in southeastern Ghana in March and November 1993 and the catches are related to environmental variables. Some 34,000 specimens, belonging to 178 morphospecies in 43 genera and 11 families, were caught with Malaise traps and light traps. Many species demonstrate differences between sampling method, seasonal occurrence, and sex-ratios, with the light trap in the second wet sunny season (November) being most efficient with respect to the diversity of the catches. A Moran index analysis for global structures indicates a major transition in the fauna from the ravine with waterfalls to the forest, and secondly, a gradient through the forest. A Geary index analysis for local structures indicates further faunal turnovers in the lower reaches of the stream. Species-environment relationships were analyzed through correspondence analysis and co-inertia analysis, allowing ordination of both species and the environment into three zones. The first co-inertia axis reveals a transition between the waterfalls in the open ravine (sites 1–3), and the stream through the riverine forest (sites 4–12), while the second co-inertia axis reveals a gradient from the lotic stream in the moist semi-deciduous forest (sites 4–8) to more lentic stretches of the stream in a gradually more depleted forest (sites 9–12). The most important environmental factors related to the species transition are: riparian moss growth (r=0.94), leaves in the stream substratum (r=0.91), forest type (r=0.90), hygropetric surfaces (r=0.88), bedrock (r=0.87), lotic [riffle] (r=0.85) and lentic [pool] (r=0.85) stretches. The most important environmental factors related to the species gradient are: lotic [riffle] stretches (r=0.92), gravel (r=0.88) and leaves (r=0.85) in the stream substratum, forest type (r=0.81), and agricultural use (r=0.76). Three clusters representing three major environmental zones (zone I, II and III) along the stream are identified by projecting the average species positions on the co-inertia plane. By analyzing the Malaise trap samples significant indicator values are found for 29 species in zone I, 16 species in zone II, and 18 species in zone III. By analyzing the light trap samples significant indicator values are found for 17 species in zone I, 57 species in zone II, and 38 species in zone III. The high diversity of caddisflies in the sanctuary might be reflected both in the geological and climatological history of West Africa, as well as in the recognition of three major environmental zones, and the clean water with high diversity of stream microhabitats favorable for Trichoptera larvae. The closed forest seems to play an important role for the Trichoptera community, and the study demonstrates the importance of protecting forested headwater streams in order to maintain a sustainable aquatic biodiversity in tropical Africa.     

Biological diversity of the Minnesota caddisflies (Insecta, Trichoptera)

The caddisfly fauna of Minnesota contains at least 277 species within 21 families and 75 genera. These species are based on examination of 312,884 specimens from 2,166 collections of 937 Minnesota aquatic habitats from 1890 to 2007. Included in these totals is my own quantitative sampling of 4 representative habitat types: small streams, medium rivers, large rivers, and lakes, from each of the 58 major Minnesota watersheds from June through September during 1999-2001. All species are illustrated herein, and their known Minnesota abundances, distributions, adult flight periodicities, and habitat affinities presented. Four species: Lepidostoma griseum (Lepidostomatidae), Psilotreta indecisa (Odontoceridae), and Phryganea sayi and Ptilostomis angustipennis (Phryganeidae) are added to the known fauna. An additional 31 dubious species records are removed for various reasons. Of the 5 determined caddisfly regions of the state, species richness per watershed was highest in the Lake Superior and Northern Regions, intermediate in the Southeastern, and lowest in the Northwestern and Southern. Of the 48 individual collections that yielded >40 species, all but 1 were from the Northern Region. Many species, especially within the families Limnephilidae and Phryganeidae, have appeared to decrease in distribution and abundance during the past 75 years, particularly those once common within the Northwestern and Southern Regions. Many species now appear regionally extirpated, and a few have disappeared from the entire state. The loss of species in the Northwestern and Southern Regions, and probably elsewhere, is almost certainly related to the conversion of many habitats to large-scale agriculture during the mid-20th century.     

Spatio-Temporal Distribution and Ecological Preferences of Coexisting Hydropsychid Species (Trichoptera) in Two Mediterranean River Basins (S Spain)

The hydropsychids of two Mediterranean river basins in southern Spain (Guadaira and Guadalete) were investigated from January 1988 to January 1989. The distribution of hydropsychids along an environmental gradient related to altitude varied depending on species. Two distinct species assemblages were observed. one located in the lower altitude sites (the “downstream assemblage” comprising Hydropsyche pictetorum, Hydropsyche exocellata and Cheumatopsyche lepida) and the other in the upper-most areas (the “upstream assemblage” comprising Hydropsyche punica, Hydropsyche infernalis, Hydropsyche instabilis), which displayed a statistically significant preference for this type of habitat. Finally, H. pictetorum, selected the lowest sites. From a temporal point of view most species displayed a high variability in density dynamics between sites, suggesting a strong plasticity in life-cycle phenology.     

Emergence and lateral dispersal of adult Plecoptera and Trichoptera from Broadstone Stream, U.K.

1. Emergence and inland dispersal of adult stoneflies (Plecoptera) and caddisflies (Trichoptera) from Broadstone Stream, an acidic and iron-rich stream in southern England, were studied over 10 months in 1996–1997. Fifteen pyramidal emergence traps were placed randomly in a 200-m stretch. Three Malaise traps were placed above the stream and six more on each side (one wooded, one open) along a transect at distances of 1, 15, 30, 45, 60 and 75 m from the channel. 2. More than 16 000 stoneflies, belonging to 11 species, and just under 400 caddisflies (22 species) were caught. Four dominant stoneflies (Leuctra fusca, Leuctra nigra, Leuctra hippopus and Nemurella pictetii) accounted for 96% and 95% of the catches in the emergence and Malaise traps, respectively. Two caddisflies (Plectrocnemia conspersa and Potamophylax cingulatus) accounted for 63% of the catch in the Malaise traps. Few caddisflies were taken in emergence traps. 3. The emergence periods of L. fusca, L. nigra and L. hippopus were well-defined and unimodal, whereas that of N. pictetii was prolonged and erratic. Overall, more females (1285) emerged than males (740). 4. Female stoneflies and caddisflies were in the majority in the Malaise traps above the stream. On land, significantly more females than males of L. fusca, L. nigra and P. cingulatus were caught. The sex ratio of the remaining species did not deviate significantly from 1:1. 5. The three Malaise traps placed above the stream caught most of the stoneflies though there was also dispersal away from the channel, the numbers caught declining with distance. Exponential models explained between 67% and 99% of the variation in numbers of individuals with distance from the channel in the four common stoneflies. Half the individuals went less than 11–16 m from the stream, while 90% travelled less than 51 m. Significantly more L. nigra and N. pictetii were caught in the woodland than on the open side, whereas L. hippopus showed no overall preference for either side.     

Microhabitat type selection of caddisfly larvae (Insecta: Trichoptera) in a shallow lowland stream

The relationship between caddisfly assemblage structure and four selected environmental variables (substrate, water depth, flow type and amount of the coarse particulate organic matter) was investigated in a Slovenian lowland stream. Caddisflies were sampled at four stream reaches according to selected microhabitat types. All together, 168 quantitative samples were taken at 21 sampling points between October 1998 and July 1999. Of 48 collected species, 30 were included in the analysis. Significant correlation was observed between species and environmental variables. As a complement to a CCA biplot representation, species assemblages within the community were also determined using cluster analysis. Nine groups and subgroups were established. Most caddisfly species prefer coarse substrate in shallow water (5–10 cm) with chute water flow, whereas few species were found on fine substrate in deep water. A significant positive correlation was found between mean substrate size and total number of species, and between indices of species richness and diversity, whereas depth did not show any correlation with these parameters. Seven species were found mostly in marginal habitats, whereas four (Potamophylax rotundipennis, Anabolia furcata, Athripsodes bilineatus and Lithax obscurus) did not show any strong preferences for selected parameters. In addition, habitat preferences were associated with the feeding types of the caddis larvae.     

Dietary variations of predaceous caddisfly larvae (Trichoptera: Rhyacophilidae,Polycentropodidae and Arctopsychidae) from British Columbian streams

The diets of larval Rhyacophilidae (Rhyacophila inculta), Polycentropodidae (Polycentropus variegatus) and Arctopsychidae (Parapsyche almota and P. elsis) from five streams in the University of British Columbia Research Forest, British Columbia (Canada), are recorded and related to feeding mode/constructional activities and prey representation in the habitat. Particular attention was paid to the extent of dietary overlap and the degree of intraspecific dietary variations between streams. An overall similarity of the diets of the study species was notable and all commonly consumed chironomid (Diptera) larvae, Simulium (Diptera) and Zapada (Plecoptera), although there was interspecific variation in the relative importance of these items. Polycentropus variegatus and Parapsyche spp. ate Baetis and Paraleptophlebia, the latter predators also consuming Hydrachnellae (Acarina). Other prey were generally of minor importance and consequently interspecific dietary overlaps were high. Differences in the range of prey consumed by predaceous Trichoptera were apparent. Free-foraging R. inculta which selectively consumed sedentary simuliid larvae had the narrowest niche breadth. Parapsyche spp. and Polycentropus variegatus foreguts generally contained an over-representation of chironomid larvae compared to their proportionate occurrence in the benthos, and these caddisflies exhibited high niche overlap. The relative importance of chironomids as food for Parapsyche spp. and Polycentropus variegatus is attributed to prey behaviour, i.e. drift, and poorly developed escape responses when they are caught on the predator's net.     

Oviposition in three species of limnephiloid caddisflies (Trichoptera): hierarchical influences on site selection

1. Oviposition site selection was studied in three trichopteran species; an undescribed species of Hydatophylax (Limnephilidae), Onocosmoecus unicolor (Limnephilidae) and Neophylax rickeri (Uenoidae), in two Coastal Range streams in California, U.S.A. 2. Hydatophylax sp. egg masses were generally found at or above the water surface on substrata near the bank in pools, where undercut banks, overhanging vegetation and rocks shaded attachment sites and provided wind protection. Onocosmoecus unicolor females deposited their egg masses exclusively above the water on moist emergent wood. The egg masses of N. rickeri were almost exclusively found in high velocity areas of riffles, where females oviposited under water and attached their egg masses to the submersed undersides of unembedded, protruding stones with large emergent surfaces. 3. For Hydatophylax sp. and N. rickeri, a hierarchical selection scheme is proposed in which females use cues at three different spatial levels (stream, stream subunit, substratum) to choose oviposition sites. Females of O. unicolor seemed to choose at only two different levels of spatial resolution (stream, substratum). 4. The formation of large aggregations of egg masses in N. rickeri and O. unicolor suggests that females actively choose oviposition sites where conspecific egg masses are already attached. The clustering of egg masses may minimise the risk of predation through the dilution effect, because egg masses of N. rickeri and O. unicolor are both attacked by dipteran predators. 5. Females of the three Trichoptera species studied are able to make a clear choice of oviposition site in the heterogeneous stream environment. In comparison with other stream microhabitats, these are characterised by stable and relatively predictable environmental conditions during the time of egg development, which is seen as the main selective pressure leading to the observed egg‐laying behaviour.     

Distribution of filter-feeding caddisflies (Trichoptera) and plankton drift in a Swedish lake-outlet stream

The objectives of this investigation were to relate the longitudinal distribution of filter-feeding caddisflies to quality and quantity of seston, and to document factors facilitating coexistence among filter-feeding species, in a 4th-order lake-outlet stream in central Sweden. A sharp decline in abundance and biomass of filtering caddisflies was evident within 1 km from the lake outlet following negative power functions. In contrast to particulate organic carbon, significant reductions of both phytoplankton and zooplankton biomass, especially some large species, were recorded between the lake-outlet and 1.9 km downstream. Differences in longitudinal and temporal distribution provide evidence of resource partitioning between filtering species included.     

Sexual dimorphism in relation to swarming and pair formation patterns in leptocerid caddisflies (Trichoptera: Leptoceridae)

North European Leptoceridae (Trichoptera) perform three types of swarming flight patterns: (1) swarming males of Athripsodesand Ceracleafly in horizontal zigzag patterns over the water surface, (2) the Mystacidesspp. perform vertical zigzag movements, and (3) the flight of males of Triaenodes unanimisMcLach. is a mixture of the horizontal and vertical zigzagging. Also three groups of pair formation behavior can be distinguished. In the first group, of Athripsodesand Ceraclea,the females fly into the male swarms, where they are grasped and carried to the riparian vegetation by the flying males with the females hanging upside-down in genitalia coupling. In the second group, a Mystacidesfemale is caught by a male, when approaching a swarm and both use their wings to fly in tandem to the shore where they copulate. In the third group, of Triaenodes bicolor(Curt.) and Oecetis lacustris(Curt.), the males fly searching for females sitting on aquatic plants and when a female is found the male lands and they copulate immediately while clinging to the plant. The different swarming and mating behaviors might have favored selection for three types of sexual dimorphism: (1) longer forewings in males than females in species which fly in copula, (2) larger eyes in males of the vertically zigzagging species, and (3) much smaller males in the group where males search for females sitting on aquatic plants. In the second group approaching females are detected by males before reaching the swarm and in the third group the female almost always mates with the male which is the first to find her. In conclusion, we suggest that females of Athripsodesand Ceracleahave a greater choice among swarming males than do females of Mystacides, T. bicolor,and O. Lacustris.     

Longitudinal patterns of production, food consumption, and seston utilization by net-spinning caddisflies (Trichoptera) in a southern Appalachian stream (USA)

Larval production of ten species of Hydropsychidae and Philipotamidae was studied at six stations along 6.4 km of a southern Appalachian stream, encompassing stream orders 1–4 and a 600 m elevation change. Species-specific production estimates ranged from 23–983 mg AFDM m^?2 yr^?1 These low values are attributed to the paucity of nutrients in these undisturbed headwater streams which reduces detrital food quality, algal growth, and production of smaller invertebrates eaten by hydropsychids. Animal food supported the majority of hydropsychid production (72%); philopotamids relied primarily on fine detritus (80%) and diatoms (15%). The contribution of animal food to caddisfly production decreased downstream, while the relative importance of filamentous algae and diatoms increased. These changes reflect the downstream decline of more carnivorous species, as well as increased primary production which accompanies the shift in lotic community metabolism from heterotrophy towards autotrophy with increasing stream order. Net-spinning caddisflies had a minor impact on seston quantity, consuming only 0.0003%-0.005% of the total seston (including invertebrate drift) passing over a m² of substrate annually. In contrast, the percentage of invertebrate drift consumed was, on the average, > 400 × higher than total seston consumption. These insects influence seston quality rather than quantity. The percentage of total seston and animal drift consumed declined downstream, indicating that turnover lengths of these materials increase with stream order. Longer turnover lengths or “spirals” result from changes in the physical characteristics of the stream, i.e., increasing discharge and stream power and decreasing numbers of retention devices (i.e., organic debris dams), which increase the downstream transport velocity of seston. Higher transport velocities reduce the rates at which these filter feeding caddisflies can process the organic inputs to a given reach of stream. Small streams (orders 1–3) appear to be most responsible for efficient processing of a stream's energy inputs.     

Trichoptera fauna from Nakhon Si Thammarat Range (southern Thailand), with the description of a new species of Rhyacophila Pictet, 1834 (Trichoptera: Rhyacophilidae)

Seventy-five species of caddisflies were found near eight waterfalls in the Tai Rom Yen National Park and the Khao Luang National Park, within Nakhon Si Thammarat Range, in southern Thailand. Rhyacophila suratthaniensis sp. n. is described and figured, based on adult males. Rhyacophila suratthaniensis sp. n. is distinguished from other species of the genus by the shape of its paramere: their basal part is broader than the apical one and is separated from it by a step; apex of the paramere bears many strong spines, which are arranged like in a toothbrush. Occurrence of Trichoptera species in the observed and neighbouring areas is discussed.

http://zoobank.org/urn:lsid:zoobank.org:pub:336401B5-DAAA-4818-90EA-5DCB1944D1F0     

Location of copper in larvae of Plectrocnemia conspersa (Curtis) (Trichoptera) exposed to elevated metal concentrations in a mine drainage stream

Using histological techniques together with transmission electron microscopy and X-ray microanalysis, copper-containing granules (which also contain significant amounts of sulphur) have been observed in the cells of the malpighian tubules and in the subcuticular region of larvae of Plectrocnemia conspersa. It is suggested that the granules in both these regions are primarily pigment granules, which provide a mechanism for taking potentially toxic concentrations of copper (and possibly other metals) out of circulation. This mechanism of metal tolerance may in part account for the reported occurrence of larvae of P. conspersa in waters with elevated concentrations of trace metals.     

Species-specific prevalence of mermithid parasites in populations of six congeneric host caddisflies of Ecnomus McLachlan, 1864 (Trichoptera: Ecnomidae)

Mermithid nematodes are entomophagous parasites and, despite being present in diverse aquatic insects, studies of caddisflies acting as definitive hosts are few and the ecological impacts on host populations are largely unknown. During a four-year study in a stream in southeastern Australia, parasitic mermithid worms were commonly found inside adult caddisflies, but only species of the genus Ecnomus McLachlan, 1864 (Ecnomidae). Ecnomus were the definitive host and parasite prevalence ranged from <1% to nearly 50% across six species. Species-specific prevalence varied little between years and was typically higher in males than in females. Parasite intensity ranged from 1 to 6 (median = 1), but did not vary between species or sexes. Infected hosts could fly, but were castrated and died when worms emerged. High prevalence and virulence (reproductive failure and death of the host) suggests that these parasites could potentially play a role in the population dynamics of some Ecnomus spp.