The Plecoptera community of a small stream in Oregon,U.S.A. *

The Plecoptera community of a small woodland stream in Oregon was studied by examining density and species composition. Four sites were studied using benthos sampling for larvae and emergence trap collections for adults. Sixteen genera and forty-three species were identified with most species occurring in relatively low numbers. A comparison with the species list from an earlier study suggested that the species composition has not changed markedly in 40 years but there were several changes in relative abundance. Species diversity of stoneflies decreased with distance from the headwaters. These changes were correlated with decrease in habitat complexity, decrease in stability of the substrate, and increase in water depth. Examples of longitudinal succession are given as a method enabling the large number of species to partition the habitat. Concurrent benthos and emergence sampling demonstrated differences in emergence success that were correlated with habitat suitability.     

Pheromone-trap catch in relation to the phenology of codling moth (Cydia pomonella)

Relationships between a pheromone-trap catch, adult emergence and penetration of fruit by first-instar larvae of Cydia pomonella were investigated from 1975 to 1977 in an orchard in South West England. For the first generation the times of moth emergence and catch in the pheromone trap were not significantly different; nor were male and female emergence times. The catch of moths of the first generation in the pheromone trap anticipated the appearance of their larvae in the fruit by 140–169 day-degrees > 10 °C. Eggs hatched after 94 day-degrees in the laboratory but in the orchard, wind and sunshine modified the microclimate so that the number of day-degrees required for egg development, as measured by standard meteorological instruments, was affected by wind and sunshine but development lasted on average about 90 day-degrees. This indicated a lag of 50–80 day-degrees between the curves for trap catch and oviposition: the pre-oviposition period in the orchard was shorter than expected from laboratory studies. In 1975 and 1976, some larvae developed to produce a second generation of moths which gave rise to a second generation of eggs and larvae, after an interval of 161 day-degrees in 1975, but only 41 day-degrees in 1976, indicating that in 1976 some eggs were laid before moths of the second generation were trapped. These results indicate that the first insecticidal spray against first-generation larvae should be applied about 140 day-degrees after the start of the reference week in which five moths of the spring brood are caught per trap. A second spray, if required to maintain insecticidal cover, should be applied about 100 day-degrees later. A spray should be applied against second-generation larvae immediately after the reference week for second-generation moths.     

Interspecific dominance amongst three species of coarse fish in Slapton Ley, Devon

Marked changes in the relative numbers of roach Rutilus rulilus (L.), rudd Scardinius erylhroplhalmus (L.) and perch Perca fIuviatilis L. , in Slapton Ley, Devon, have been observed over the period 1967–1978. Historically, the lake had been dominated by rudd and perch; significant numbers of roach were not thought to be present until 1967. From then onwards the roach population exhibited a considerable expansion, apparently replacing the rudd, which had virtually disappeared by 1974. In 1975 extensive mortalities of roach were caused by the pseudophyllidean cestode Ligula intestinalis L. During 1976 and 1977 larger number of rudd, belonging to the 1975 and 1976 year classes, were present, suggesting that the roach mortalities might be giving the rudd a chance to recover. However, very few rudd were present during 1978, possibly because lower incidences of ligulosis during 1976–1978 had allowed the roach to recover from the main outbreak of the disease in 1975, and to replace the rudd for the second time. Evidence from trap catches indicated that the perch population had shown a consistent decline between 1970 and 1977. The major phase of this decrease occurred between 1971 and 1973, when the roach population was increasing the most rapidly. Comparisons were made with changes in fish populations in other localities. The major reason for the changes observed was thought to be a competitive relationship between the plankton feeding younger stages, with roach being the dominant species, although other factors may also have been involved.     

The macrobenthos of the river IJssel

Summary This survey of the macrobenthos of the River IJssel, a branch of the River Rhine, was conducted in 1973, 1975, 1976 and 1977. The water quality was poor in 1973 and 1976 and relatively good in 1975 and 1977.The numbers of macroinvertebrate species and numbers of individuals in the stone samples taken from the jetties were lowest in 1976 and highest in 1977.The species composition of the Tubificidae showed a marked difference in various types of substratum at one locality.Decrease of water quality since a study of LAUTERBORN (1918) is reflected by impoverishment of the fauna; for instance, insects have disappeared to a large extent.     

Changes in experimental gillnet catches from the Kafue Floodplain, Zambia, since construction of the Kafue Gorge Dam

The Kafue Floodplain fishery produces an annual fish yield of about 5000 tonnes. The 1971 closure of the Kafue Gorge Dam downstream from the floodplain modified flooding patterns. Pre-impoundment studies predicted this modification would increase fish stocks. Experimental gillnets set in 1975 and 1976 caught 18 species on a regular basis, nine of which were abundant enough for comparison with catches in similar gillnet samples taken prior to completion of the Kafue Gorge Dam. Of these nine species, experimental gillnet catches of three predator species were smaller in 1975–76 than in 1969–70. Catches of only one species increased significantly. Whether this change is due to the modified flooding pattern is unclear; unusually dry flood conditions in 1973 and increased fishing effort may have contributed.     

Climatic change is advancing the phenology of moth species in Ireland

Recent increases in global temperatures have contributed to advancing phenology of plants and animals. These increases in temperature have been shown to affect the phenological phases (phenophases) of plants and birds in Ireland, but less is known about the effect on the phenophases of Irish insects. Records of the flight periods of 59 species of Irish moths over the past 35 years (1974–2009) were obtained from a public monitoring group. Observations were analysed across the country using generalized additive models (GAMs) weighted by total yearly population numbers for each species. The results of the statistical analyses showed that 45 of the 59 species studied have a significantly earlier first sighting date now than when observations began. With this earlier emergence, 44 of the 59 species also have a significantly longer flight season over the same 35‐year period. The extent of these changes varies across the country and by species life history. In particular, species emerging in spring are advancing at a much faster rate than species emerging during the summer. Many of these changes in first sighting are negatively correlated with rising temperatures in Ireland, particularly in late spring and early summer (May and June). The variation in phenological advancement in the moth species of Ireland is extremely complex and may be influenced more by species life history than by the phenology of interacting species, such as host plants.     

Distribution of benthic macroinvertebrates in an artificially destratified reservoir

A total of 76 taxa of benthic macroinvertebrates as collected from Ham's Lake, Oklahoma, during 1974 and 1975. The composition and density of the benthic assemblage was similar to that of other Oklahoma reservoirs. The number of species and density of macroinvertebrates decreased from March to the end of July, 1975 Species diversity and biomass did not change significantly with time. Number of species and species diversity decreased with depth on all sampling periods. The most pronounced changes occurred between 4 and 5 m during periods of thermal stratification and hypolimnion anoxia. Artificial destratification removed the thermocline from Ham's Lake within 2 wk. More gradually, the deep waters were reoxygenated. Destratification did not substantially alter the depth distribution of benthic macroinvertebrates until oxygen level of the deep water was increased. Research supported with funds from the Oklahoma Water Resources Research Institute and the Bureau of Reclamation.     

Increasing abundance and diversity in the moth assemblage of east Loch Lomondside,Scotland over a 35 year period

Macro-moths caught in a Rothamsted trap, operating from 1968 to 2003 as part of the Rothamsted Insect Survey, were used to investigate the long-term population trends of moth populations on East Loch Lomondside. In total 367 species of macro moth were recorded during this study. Over the 35 years of this study, an increase was recorded in both the overall number of individuals and moth diversity. Mean annual temperature significantly predicted the change in moth diversity but not number of individuals caught. Four of the most consistently abundant species, collectively constituting 27% of the average annual catch, were subjected to more detailed analysis. The three species that emerge during the summer months Eulithis populata (the northern spinach), Hydriomena furcata (july highflier) and Idaea biselata (the small fan-footed wave) became more abundant throughout the study period, (although for the latter species not significantly so). For Eulithis populata and Idaea biselata their emergence time became earlier, over the study period and in Eulithis populata and Hydriomena furcata, the flight duration also became longer. In contrast, the species that emerges as an adult during autumn and winter, Epirrita dilutata (the november moth) did not exhibit a significant change in abundance, emergence date or flight duration in this study. The results suggest that climate change is at least in part, responsible for the observed changes in species dynamics.     

Seasonal occurrence of coccoliths in sediment traps from West Caroline Basin, equatorial West Pacific Ocean

Coccolith fluxes were investigated by sediment trap studies in the West Caroline Basin, which is located in the equatorial western Pacific. The investigation was conducted from June 1991 to March 1992 at two water depths, 1592 and 3902 m, as part of the Northwest Pacific Carbon Cycle Study (NOPACCS) program. Two seasonal maxima of coccolith fluxes were observed during September–early October and late December–January. The average coccolith and coccosphere fluxes at the depth of the shallow trap were 1800×10⁶ coccoliths m⁻² day⁻¹ and 1.9×10⁶ coccospheres m⁻² day⁻¹, respectively. The flux of coccoliths followed the same trend as the total flux, and was closely correlated with the flux of organic matter flux. Florisphaera profunda, Gladiolithus flabellatus, Gephyrocapsa oceanica, Umbilicosphaera sibogae var. sibogae, Emiliania huxleyi, and Oolithotus fragilis were the most abundant species together comprising more than 85% of the total flora. Observed seasonal changes of the species composition of coccolith flora, as well as analysis of the R-mode cluster, revealed that during the summer, the assemblage was marked by the dominance of G. oceanica and U. sibogae. However, during the winter, the assemblage was dominated by E. huxleyi and O. fragilis. These assemblage changes were influenced by monsoonal events, which were observed off the New Guinea coast. F. profunda dominated the community in the shallow trap throughout most of the year; peak values of this species were recorded during the winter. The coccosphere assemblage was dominated by G. oceanica at both water depths. In the deep trap, the sedimentation pattern was similar to that observed at the shallow depth. Mean coccolith and coccosphere fluxes at the deep trap were 2000×10⁶ coccolith m⁻² day⁻¹ and 0.08×10⁶ coccospheres m⁻² day⁻¹, respectively. The increase in coccolith flux with water depth suggests a lateral influx. The estimated average daily mass of CaCO₃ flux in coccoliths and coccospheres was 16.6 mg m⁻² day⁻¹ at the 1592 m trap and 17.9 mg m⁻² day⁻¹ at the 3902 m trap, respectively. These calculated values contributed only 23.3% to the total CaCO₃ flux at the shallow trap and 27.9% at the deep trap.     

The abundance and distribution of caddisflies (Insecta: Trichoptera) caught by emergence traps in the 'Ritrodat' research area of the Lunzer Seebach (Lower Austria) from 1980 to 1982

SUMMARY. 1. Adult Trichoptera were caught during 3 years (1980–82) in the ‘Ritrodat’ research area of the Upper Lunzer Seebach. a mountain brook near Lunz. Lower Austria, using a set of thirty pyramid type emergence traps. During the three collecting periods (112 collecting days) a total of 1810 specimens were caught. The most abundant species were Micrasema minimum McL. (Brachycentridae). Rhyacophila vulgaris Pictet (Rhyacophilidae), and the three Iimnephilid species Potamophylax cingulatus Steph., Allogamus auricollis Pictet and Ecclisopteryx guttulata Pictet. 2. In six species (Micrasema minimum, Rhyacophila vulgaris, Atlogamus auricollis, Ecclisopteryx guttulata, Drusus biguttatus Pictet, Chaetopteryx fusca Brauer) the sex ratio was significantly different from 1:1. In Micrasema minimum 422 females were caught but only three males. 3. In each year there were peaks in total emergence in early summer and early autumn. 4. The length of the emergence period of the most abundant species ranged from 38 days in Micrasema minimum to 210 days in Rhyacophila vulgaris (mean values 1980–82); there was also a difference in the intensity of emergence in these species: the percentage of time required for 50% of the animals to emerge (0%=onset of emergence, 100%= emergence completed) was 16% in Allogamus auricollis but 71% in Rhyacophila vulgaris (mean percentages 1980–82). 5. The distribution pattern of individuals per trap was tested against a Poisson distribution; in all three years the distribution was contagious. 6. The dry weight of specimens of Drusus biguttatus, Micrasema minimum. Ecclisopteryx guttulata and Wormaldia copiosa McL. was measured and. together with published dry weight values of other species (Malicky, 1976), these data were used to estimate the biomass emerging annually of twenty-three species of Trichoptera (99.2% of emergence, 1980–82). This was equivalent to 35.3 kJ m^?2 in 1981 and 32.5 kJ m^?2 in 1982.     

The role of Anthocoris species (Hemiptera: Anthocoridae) in the integrated control of the damson-hop aphid (Phorodon humuli)

Field studies in 1974, 1975 and 1976 investigated integrated control of the damson-hop aphid Phorodon humuli on hops. After the aphicidal effects of an early-season soil drench of mephosfolan had declined, natural enemies controlled the aphids for the remainder of the season. Anthocorid bugs, particularly Anthocoris nemoralis, were the most abundant predators. In each year a rapid decline in aphid numbers occurred in mid- to late-July, coinciding with the peak numbers of fourth and fifth instar larvae and adults, the most voracious anthocorid stages. Aphids in the cones remained under control for the rest of the season in 1974 and 1975, and increased in 1976 but damaging numbers did not develop. When predators were excluded by caging mephosfolan-treated bines, high aphid densities developed on the leaves, and the cones were heavily infested. Plants not treated with an insecticide were almost completely defoliated by late-July. Heavily infested ‘missed bines’, due to uneven uptake of mephosfolan, attracted large numbers of anthocorids, which later dispersed into the surrounding plants.     

Testing temperature effects on woodboring beetles associated with oak dieback

A warmer climate may potentially have a strong effect on the health status of European oak forests by weakening oak trees and facilitating mass reproduction of wood boring insects. We did a laboratory experiment in Slovakia to study the response of major pest beetles of oak and their parasitoids to different temperature regimes as background for predicting climatic effects and improving management tools of European oak forests. With higher temperatures the most important oak pest Scolytus intricatus emerged much earlier, which indicate that completion of a second generation and increased damage further north in European oak forests may be possible. Lower temperatures gave longer larval galleries and more offspring per parents but still lower beetle production due to semivoltine life cycle. For buprestids and longhorn beetles warmer temperatures resulted in more emerging offspring and a shift towards earlier emergence in the same season, but no emergence in the first season indicated that a change to univoltine populations is not likely. Reduced development success of parasitoids at the highest temperatures (25/30 °C) indicates a loss of population regulation for pest beetle populations. A warmer climate may lead to invasion of other population-regulating parasitoids, but also new serious pest may invade. With expected temperature increases it is recommended to use trap trees both in April and in June, and trap trees should be removed within 2 months instead 1 year as described in the current standard.     

Phenological patterns of neotropical lotic chironomids: Is emergence constrained by environmental factors?

Abstract In this paper we analyzed the emergence phenology of a highly diverse chironomid assemblage to test for association between emergence and some environmental variables and for the presence of synchrony in emergence. We used a time series of 48 weekly samples from a tropical low order forested stream (south‐eastern Brazil) to describe how this assemblage varied in an intra‐annual scale. An eigenvector‐based filtering approach was adapted to create temporal variables that could be used in our multiple regression analyses, trying to overcome the problems of temporal autocorrelation. Emergence of the Chironomidae, two subfamilies, concordant species, and of dominant species was not related to rainfall, temperature, moon phase or photoperiod. Taxonomic composition and species richness did not change across time. The number of emerging individuals of the subfamily Orthocladiinae was significantly related to temperature and to temporal filters. The inclusion of the temporal filters into the analyses almost eliminated autocorrelation in the regression residuals. We detected interspecific synchrony in a group of species, but an absence of trends and periodicity in chironomid emergence, which was not related to environmental variables. This suggests that unknown factors, differing from those known to control emergence in temperate regions, operate in the tropics. The erratic behaviour of the analyzed series raises the question of whether chaotic dynamics may generate this variability.     

Composition and Structure of Zooplankton Communities in Eighteen Arctic and Subarctic Lakes

The factors influencing the composition and structure of zooplankton communities in 18 lakes in the Canadian arctic and subarctic were determined during 1975 and 1976. Phytoplankton were consumed in very low numbers by all species (Diaptomus sicilis, Heterocope septentrionalis, Cyclops scutifer, Daphnia longiremis, Bosmina longirostris, Holopedium gibberum, Keratella cochlearis, Kellicottia longispina) and therefore differences in algal productivity among the lakes had little effect on the zooplankton. Variations in surface area, maximum water depth, pH and the ionic composition of the water were also unimportant in controlling the communities. However, low temperature exerted strong influence over the diversity, abundance, fecundity and vertical distribution of most species.     

Distribution and abundance of adult Opomyza florum (Diptera: Opomyzidae) in cereal crops and grassland

From 1971 to 1979 counts were made of the numbers of Opomyza florum adults found in vacuum net samples taken from cereal and grass fields on a 62-km² study area in West Sussex. In 2 years, 1974 and 1975, counts were made of the numbers of adults found in similar samples taken from hedgerow grasses. In all years, numbers of adults were highest in winter wheat crops; relatively few were found in other autumn- or spring-sown cereals or in grass fields. Mean numbers (/m²) in winter wheat in June varied from 33.0 in 1974 to only 0.9 in 1977. In most years, the first adults were found in June in winter wheat; numbers reached a peak in July and then declined rapidly. More adults were usually found in winter wheat crops that followed winter wheat in the rotation than in those following grass. Adults were also more abundant in June in winter wheat crops sown relatively early than in those sown late. The current tendencies towards earlier drilling of winter wheat and to the growth of successive wheat crops could increase the pest status of O. florum.     

A comparison of the zooplankton of Lake Kainji and of the Rivers Niger and Swashi

Seventy-nine taxa of periphyton were collected on Plexiglas plates at seven stations in the three streams between March, 1975, and February, 1976. More taxa and lower densities were generally observed at the upstream stations in the creeks than at the downstream stations resulting in greater species diversity values at the upstream stations. Species diversity was generally lower in the river than in the creeks, reflecting the lower numbers of taxa and the presence of several abundant species. Species diversity did not reflect extremes in physiochemical conditions. Although several different species were abundant in the streams during the present study, the most commonly occurring dominants were Gomphonema olivaceum and species belonging to the genera Navicula and Nitzschia. No consistent trend was observed in ash-free weight; however, the concentration of chlorophyll a was generally greater at the downstream stations in the creeks than at the upstream stations.     

Detection of stored-wheat beetle species and estimation of population density using unbaited probe traps and grain trier samples

Field studies were conducted in order to compare the effectiveness of unbaited probe traps and grain trier samples in the detection of several beetle species. On June 15, 1997, fourteen probe traps were placed in three steel bins containing wheat in Central Greece. Two of them were inserted in the central zone of the bulk, five in the half of the bin radius (median zone) and seven near the bin wall (distal zone). From June 30 up to and including January 1998, the traps were checked for adult beetles every fifteen days (15 sampling dates in total). On each date, samples were also taken from spots adjacent to trap locations, using a grain trier. The mean temperatures recorded near the bulk surface decreased by an average of 1.16 °C per sampling date. Twenty-four species, belonging to 14 families of Coleoptera were found. The most abundant species in the traps were Cryptolestes ferrugineus and Tribolium castaneum, while Sitophilus oryzae was the most abundant in the samples. Significantly greater numbers of adults were found in traps than in samples, during the whole sampling period; traps also detected adults in most locations while in the corresponding samples no adults were found. Significantly higher numbers of adults were found in the central sampling zone, using both devices. Taylor's power law parameters showed that in both sampling methods the most abundant species showed aggregated spatial patterns. Although the correlation coefficient values between trap catches and number of adults per trier sample differ significantly from zero (P < 0.01) in a high number of sampling dates, it can be concluded that traps are poor indicators of population density. The accuracy provided as a percentage of the mean, decreases exponentially with the increase of the mean value. Based on traps, the desired accuracy level (35%) is not achievable even in higher mean values or even with high numbers of traps. On the contrary, with trier samples it is possible to estimate population density with a relatively low number of sampling units. Significant differences in the required number of sampling units (sample size) were noted among species.     

Population dynamics of two snail species,Planaxis sulcatus and Cerithium moniliferum,and their trematode species at Heron Island,Great Barrier Reef

Summary The population dynamics of the prosobranch snail Planaxis sulcatus and its trematode parasites on 600 m of beachrock on the southern side of Heron Island, Great Barrier Reef, were studied. Populations of Planaxis show little mixing, due to lack of long-distance movements. From March 1973 to June 1975, an increase in the numbers of small and medium-sized snails occurred, but the biomass (dry tissue weight) of the snail population did not change. Snails were infected with one species of Aspidogastrea and six species of cerariae. Infections with cercariae did not significantly affect the relative weight of the snails. Multiple infections were random, i.e. neither negative nor positive interactions between trematode species could be demonstrated. Proportions of uninfected snails and snails infected with various trematode species remained more or less constant from July 1973 to February 1975.The population dynamics of the prosobranch snail Cerithium moniliferum and its 11 species of cercariae and one species of Aspidogastrea in a small area at Heron Island were studied. Numbers of large snails decreased and numbers of small snails increased from August 1973 to June 1975. The biomass of the Cerithium population increased only slightly. Prevalence of infection changed significantly only in large snails.Infections of Cerithium moniliferum and Peristernia australiensis with an aspidogastrid species decreased strongly from January 1971 to March/April 1972 and had not recovered by mid 1975.Seasonal fluctuations could not be demonstrated for any of the snails or parasites.The data for Planaxis suggest equilibrium conditions and saturation of the habitat.     

A seasonal study of the haematology of wild freshwater fish

Various haematological values of wild yellowfish ( Barbus holubi ), carp ( Cyprinus carpio ) and two species of mudfish ( Labeo umbratus and Labeo capensis ) were examined on a seasonal basis from May 1975-April 1976, obtained from three different localities. Haematological values of fish of different length groups (from all four species) were studied at one locality during winter only. (June 1976-August 1976). Seasonal variations were observed in all of the parameters studied but no sexual differences were found and no significant changes in the haematology could be related to breeding season. Wide individual variations were evident in fish of different length groups and no correlation existed between fish length (and mass) and haematological values.     

Emergence of Chironomidae from the shallow eutrophic Lake Kasumigaura,Japan

Seasonal chironomid emergence was monitored in the shallow eutrophic Lake Kasumigaura and 18 species were collected with a battery-operated light trap fixed on a floating stage and with surface emergence traps. During October–December, samples in the light trap comprised exclusively Tokunagayusurika akamusi (Tokunaga) and small numbers of one or two other species. T. akamusi, Procladuis (Holotanypus) culiciformis (L.), and Chironomus plumosus (L.) constituted 91.6% of the annual catch of chironomid adults. The predominance of T. akamusi (75.3 % of chironomid catch) and the high ratio (13) of T. akamusi to C. plumosus was more marked in this lake than other Japanese eutrophic lakes. Glyptotendipes tokunagai Sasa and Dicrotendipes pelochloris (Kieffer) were also caught abundantly with the light trap, but not with surface traps, indicating these were littoral species. The dry weight of emerging adults during May–December 1982 was 2.87 g m^–2, of which 1.92 gm^–2 (67%) was T. akamusi and 0.67 gm^–2 (23%) C. plumosus and 0.23 g m^–2 (8%) Clinotanypus sugiyamai Tokunaga and 0.03 gm^–2 (1%) P. (H.) culiciformis. The weight of emerging Tanypodinae was much higher than the annual mean larval biomass or estimated larval production, which have been due to underestimating the population density using an Ekman-Birge dredge. High numbers of individuals and species of chironomids were caught during April–July, presumably as a result of the high food supply for chironomid communities.