August Period Research Articles

Rossby Wave Propagation and Teleconnection Patterns in the Austral Winter

Abstract Observational evidence of and theoretical support for the Northern and Southern Hemisphere teleconnection patterns in the austral (Southern Hemisphere) winter are examined through an upper troposphere streamfunction teleconnectivity map and time-lag cross-correlation analysis using ECMWF initialized analysis 2OO-hPa winds for the 11 June–August periods from 1979 to 1989. As was previously found for the Northern Hemisphere winter, the regions of strong teleconnectivity, particularly in the winter hemisphere, tend to he oriented in the zonal direction and coincide with the location of the major jet streams. Although equatorward propagation from the Northern and Southern Hemispheres is observed, little evidence of cross-equatorial propagation has been found. For comparison, the response of a barotropic model, linearized about a climatological 300-hPa June–August time-mean flow to localized forcing is determined. It is found that the activity tends to be trapped inside each of the Southern Hemisphere...

Biological control potential of Dinarmus basalis (Rond.) (Hymenoptera: Pteromalidae), a larval-pupal ectoparasitoid of the pulse beetle, Callosobruchus chinensis (L.)

The parasitic wasp, Dinarmus basalis (Rond.), was introduced at six densities to suppress residual populations of ca 600 pulse beetle, Callosobruchus chinensis (L.), breeding in red lentil debris in a 46.24 m 2 room. The release rates were 5, 10, 20, 30, 40 and 50 pairs of parasitoids. The highest density, 50 pairs, suppressed the C. chinensis population 100% in the April–May period, but in the July–August period, 30 pairs could achieve this result. More progeny per female parasitoid were produced at the lower parasitoid densities than at the higher levels in both periods. In another test, ca 500 pulse beetles per 275 g of lentils, kept separately in each of three types of bags (amemian, jute and polypropylene) were exposed in the room to 50 pairs of parasitoids. Highest percentage of suppression and parasitism occurred in amemian bags and lowest in polypropylene bags when a single release of 50 pairs of D. basalis were made during both periods.

Prenatal infection with Setaria marshalli (Boulenger 1921) in cattle

A full year's epidemiological study was conducted in Japan on prenatal infection with Setaria marshalli in cattle. A total of 65 bovine fetuses of abattoir origin, both male and female of 2–9 months of age, were examined postmortem. Results showed that S. marshalli adult worms were detected in the peritoneal cavity of six bovine fetuses of 7–9 months of age during the months of October–December, but not in fetuses of any age during the months of January–September. Infection was not detected in any fetuses under the age of 7 months at any given month of the year. This is the first observation to demonstrate prenatal S. marshalli infection in fetuses. Since S. marshalli has not been detected in cattle older than 2 years, it is speculated that prenatal infection is the common type, while postnatal infection is rather uncommon. Considering fetal age and the seasonal factor, a fetus of age 4–5 months would most frequently develop prenatal infection in the June–August Period, when mosquitoes are active as vectors. It is concluded, therefore, that S. marshalli prenatal infection develops during the middle stage of fetal life in summer.

Diurnal and seasonal variations of sporadic meteor parameters

Diurnal variations of the median echo durations of sporadic meteor echoes during August and December-January periods are discussed. It is shown that differences between seasonal distributions result from the superposition of simultaneous diurnal effects controlling the electron loss processes in the ionized meteor trail.

Reducing discrepancies in atmospheric heat budget of Tibetan Plateau by satellite-based estimates of radiative cooling and cloud-radiation feedback

Past investigations of the summertime heat budget over the Tibetan Plateau have not included detailed estimates of radiative cooling (Q R ) nor have they carefully considered the effects of cloudiness on this term. The various attempts to eyaluate different combinations of heat and moisture budget torms and to understand the sources of energy to the summer armospheric heat source over the plateau are not in agreement, partly because of remaining discrepancies in the radiative and turbulent flux components, and partly because until recently, the conventional data sets needed for independently estimating the total heating and moistening terms have been incomplete. The uncertainties in the radiative term have also led to difficulties in assessing the uncertainties in the other budget terms, since no study to date has assembled a complete enough data set to allow a unified calculation of all budget quantities or to obtain budget closure. Recently published results of Yanai and his colleagues involving apparent heat source calculations for the plateau region based on a much improved FGGE data set, have motivated the examination of whether more detailed radiative calculations can help resolve past discrepancies in the budget terms on a monthly time scale. This study uses a continuous time series of 22-km resolution INSAT geosynchronous satellite measurements and ECMWF profile analyses in conjunction with medium spectral resolution radiative transfer models to estimate the slicrtwave and longwave components of the radiative cooling term and the role of cloudiness on these components for the 1988 summer period. The calculations reveal both meridional and zonal structure in radiative divergence across the plateau associated with the substantial gradients of cloudiness and aridity that dominate the summertime plateau climatology. The calculations also indicate that the magnitudes of both cloud-induced shortwave heating and longwave cooling over the plateau are much greater than over low-elevation regions. Moreover, since cloud-induced longwave cooling exceeds cloud-induced shortwave heating, the bulk effect of clouds is to radiatively cool the plateau atmosphere. The high resolution calculations are reduced to monthly averaged budget quantities for analyzing whether existing discrepancies in the plateau heat budget can be resolved. Although there is no means to rigorously verify the accuracies and representativeness of the individual budget terms, the new radiative estimates combined with the most reliable current estimates of total heating and turbulent fluxes, produce near closure (within 4%) of the plateau heat budget for the June to August period.

Climatology of the SKYHI Troposphere–Stratosphere–Mesosphere General Circulation Model

Abstract The long-term mean climatology obtained from integrations conducted with different resolutions of the GFDL “SKYHI” finite-difference general circulation model is examined. A number of improvements that have been made recently in the model are also described. The versions considered have 3° × 3.6°, 2° × 2.4°, and 1° × 1.2° latitude–longitude resolution, and in each case the model is run with 40 levels from the ground to 0.0096 mb. The integrations all employ a fixed climatological cycle of sea surface temperature. Over 25 years of integration with the 3° model and shorter integrations with the higher-resolution versions are analyzed. Attention is focused on the December–February and June–August periods. The model does a reasonable job of representing the atmospheric flow in the troposphere and lower stratosphere. The simulated tropospheric climatology has an interesting sensitivity to horizontal resolution. In common with several spectral GCMs that have been examined earlier, the surface zonal-mea...

On the Dynamical Basis for the Asian Summer Monsoon Rainfall-El Niño Relationship

The dynamical basis for the Asian summer monsoon rainfall-El Niño linkage is explored through diagnostic calculations with a linear steady-state multilayer primitive equation model. The contrasting monsoon circulation during recent El Niño (1987) and La Niña (1988) years is first simulated using orography and the residually diagnosed heating (from the thermodynamic equation and the uninitialized, but mass-balanced, ECMWF analysts) as forcings, and then analyzed to provide insight into the importance of various regional forcings, such as the El Niño–related heating anomalies over the tropical Indian and Pacific Oceans. The striking simulation of the June–August (1987–1988) near-surface and upper-air tropical circulation anomalies indicates that tropical anomaly dynamics during northern summer is essentially linear even at the 150-mb level. The vertical structure of the residually diagnosed heating anomaly that contributes to this striking simulation differs significantly from the specified canonical vertical structure (used in generating 3D heating from OLR/precipitation distributions) near the tropical tropopause. The dynamical diagnostic analysis of the anomalous circulation during 1987 and 1988 March–May and June–August periods shows the orographically forced circulation anomaly (due to changes in the zonally averaged basic-state flow) to be quite dominant in modulating the low-level moisture-flux convergence and hence monsoon rainfall over Indochina. The El Niño–related persistent (spring-to-summer) heating anomalies over the tropical Pacific and Indian Ocean basins, on the other hand, mostly regulate the low-level westerly monsoon flow intensity over equatorial Africa and the northern Indian Ocean and, thereby, the large-scale moisture flux into Sahel and Indochina. The anomalous summer monsoon rainfall over Asian/African longitudes in turn, forces modest surface westerlies over the equatorial western and south tropical Pacific, which contribute positively to the ongoing El Niño's development.

The Relationship of Urgent Hospital Admissions for Respiratory Illnesses to Photochemical Air Pollution Levels in Montreal

The relationship between the number of daily urgent hospital admissions for respiratory illnesses (31 hospitals) and ambient air pollution in Montreal, Canada, was investigated for warm periods between 1984 and 1988. Air pollutants included 1-hr and 8-hr maximum ozone, estimated particulate matter ≤10 μm in aerometric diameter (PM10), and estimated sulfate (SO42−) fraction of PM10. Regression analyses controlled for seasonal and day-of-week trends, autocorrelation, temperature, and relative humidity. For July and August periods, there was a statistically significant (P < 0.01) univariate relationship of all respiratory admissions to 8-hr maximum ozone, which became nonsignificant when coregressed with temperature. Levels of ozone which never exceeded the U.S. National Ambient Air Quality Standard (NAAQS) of 120 ppb and high intercorrelations between ozone, particulates, and temperature may explain this finding. Asthma admissions in the May-October periods increased by 2.7% over mean levels for each 12 μg/m3 increase in PM(10) levels 3 days prior to the admission day (95% confidence interval, 0.7 to 4.8%). In the July and August periods, hospital admissions for respiratory illnesses excluding asthma were 9.6% higher (95% confidence interval, 0.5 to 18.7%) when estimated SO42− had exceeded 8.1 μg/m3 4 days prior to the admission day compared to days when SO42− was at or below this level. There were no significant (P < 0.05) associations of a reference group of nonrespiratory admissions to air pollution after controlling for weather. The above results were found despite levels of PM10 which never exceeded the NAAQS of 150 μg/m3. The associations found are relevant to public health, since hospital admissions are expected to be accompanied by considerably more frequent occurrences of less serious outcomes. The present findings suggest that particulate air pollution during photochemically active periods is related to respiratory morbidity in Montreal.

Some aspects of the West African monsoon circulation As deduced from a geostationary satellite

This paper focusses on some aspects or the West African monsoonal circulation observed during the period 15 July-l0 August 1979 of the PGGE, as derived from the satellite cloud windvectors. Temporal averages of the computed winsfields reveal that the flow at the low level is southerly (monsoonal), and Its line of discontinuity with the continental northeasterly was found at approximately 16°-18°N, lying about 300 km south of the accepted mean position. At both the middle and upper tropospheres the flow is easterly with axis about 12o-14,N and, latitude 8 No respectively, such that it is a circulation south of the axis and northwards, it is anticyclonic. The satellite-observed tropospheric circulation IS then discussed in relation to the, weather manifestations over the sub-region typical of the July / August period.&#x0D; &#x0D; The mass fields obtained from our gridded satellite-winds indicate that inflow into the land area occur mainly at the lowest layer (1000:850 hPa), whereas at the upper, levels (that is, above 850 hPa) it is predominantly an outflow, The tropospheric average gives a net mass for divergence from within the area, The significance of this result in relation to the observed weather phenomenology of a temporary cessation of the monsoon precipitations occurring about the peak of the season IS also discussed.

A simulation of the Cerro Hudson SO2 cloud

An isentropic trajectory model is used to simulate the evolution of the southern hemisphere SO2 cloud associated with the eruption of Cerro Hudson. By matching the parcel trajectories with total ozone mapping spectrometer SO2 retrievals, the principal stratospheric injection region is determined to be between 11 and 16 km in altitude. This region is characterized by weak wind shears and is located just poleward of the subtropical jet in the outer fringe of the stratospheric polar vortex. The lack of wind shear in the injection region explains the slow zonal dispersal of the SO2 cloud which was still clearly observed 19 days after the eruption. The trajectory model simulation of the SO2 cloud shows good agreement with observations for 7 days after the eruption. Using the potential vorticity and potential temperature estimates of the initial eruption cloud, the cloud position relative to the polar night jet is shown to be nearly fixed up to September 2, 1991, which was as long as the cloud was observed. This result suggests that the lower stratospheric polar and mid‐latitude regions are nearly isolated from each other during the late August period.

Dry matter yield and nitrogen recovery from bromegrass in south‐central Alberta as affected by rate of long‐term nitrogen applications

Abstract A field experiment was conducted on a Thin Black Chemozemic soil at Crossfield in south‐central Alberta to determine the effect of long‐term application of ammonium nitrate on dry matter yield (DMY), protein yield (PY), protein concentration, N use efficiency and recovery of N applied to bromegrass (Bromus inermis Leyss.) grown for hay. The N fertilizer was applied at 0, 56, 112, 168, 224, 280, and 336 kg N/ha in early spring of every year from 1968 to 1986. The DMY increased with applied N achieving a maximum at 224 kg N/ha, though the rate of increase in DMY from N fertilization was greatest with the first two increments applied (i.e. 56 and 112 kg N/ha). Protein yield and protein concentration maximized at 336 kg N/ha. The DMY was greater with a single‐cut system than with a double‐cut system. The DMY varied from year to year, but it was not closely related to precipitation received during the April to August period (R2 = 0.37). However, in some years low DMYs were associated with low precipit...

Phytoplankton pigment patterns and wind forcing off central California

We use a 4‐year time series of high‐resolution coastal zone color scanner imagery to study mesoscale variability in phytoplankton pigment (as a surrogate for biomass) distributions off central California during the spring‐summer upwelling season. We use empirical orthogonal functions to decompose the time series of spatial images into its dominant modes of variability. Similarly, we analyze wind fields derived from the Fleet Numerical Oceanography Center pressure fields. The results from these analyses are used to investigate the coupling between wind forcing of the upper ocean and phytoplankton distributions on mesoscales. Prior to the spring transition, wind stress is dominated by strong northward conditions, and pigment is low and relatively uniform throughout the California Current domain. The first strong southward wind event soon results in a bloom of phytoplankton that is also uniformly distributed offshore. Nearshore values fluctuate relatively little in response to variations in wind forcing. After the spring transition, the wind becomes more steady (southward) and the fluctuations are dominated by changes in the strength of the curl. During southward events, the curl tends to become more positive. Depending on the fluctuations and strength of these curl episodes, filaments begin to form at particular locations. The overall pigment concentration in the California Current drops as a larger fraction of the pigment is distributed within the filaments. The filaments also tend to become shorter during this period, which starts soon after the spring transition and usually reaches its maximum intensity in early summer. Winds (and curl) become much weaker in the mid‐July to August period, and the filaments become much less prominent in terms of concentration and their length increases. Isolated wind events occasionally reinvigorate the filaments. A final bloom in the fall occasionally appears with spatial structure similar to the spring bloom. We conclude that wind forcing, in particular the curl of the wind stress, plays an important role in the distribution of phytoplankton pigment in the California Current. Although the underlying dynamics, especially of the filaments, may be dominated by processes other than forcing by wind stress curl (such as eddies or topographically induced instabilities), it appears that curl may force the variability of the filaments and hence the pigment patterns.

Estimated Loss of Juvenile Salmonids to Predation by Northern Squawfish, Walleyes, and Smallmouth Bass in John Day Reservoir, Columbia River

–We estimated the loss of juvenile salmonids Oncorhynchus spp. to predation by northern squawfish Ptychocheilus oregonensis, walleyes Stizostedion vitreum, and smallmouth bass Micropterus dolomieu in John Day Reservoir during 1983–1986. Our estimates were based on measures of daily prey consumption, predator numbers, and numbers of juvenile salmonids entering the reservoir during the April–August period of migration. We estimated the mean annual loss was 2.7 million juvenile salmonids (95% confidence interval, 1.9–3.3 million). Northern squawfish were responsible for 78% of the total loss; walleyes accounted for 13% and smallmouth bass for 9%. Twenty-one percent of the loss occurred in a small area immediately below McNary Dam at the head of John Day Reservoir. We estimated that the three predator species consumed 14% (95% confidence interval, 9–19%) of all juvenile salmonids that entered the reservoir. Mortality changed by month and increased late in the migration season. Monthly mortality estimates ranged from 7% in June to 61% in August. Mortality from predation was highest for chinook salmon O. tshawytscha, which migrated in July and August. Despite uncertainties in the estimates, it is clear that predation by resident fish predators can easily account for previously unexplained mortality of out-migrating juvenile salmonids. Alteration of the Columbia River by dams and a decline in the number of salmonids could have increased the fraction of mortality caused by predation over what it was in the past.

Nesting of the Montpellier snake (Malpolon monspessulanus) inside rabbit warrens at Doñana National Park (SW Spain): phenology and a probable case of communal nesting

The reproductive biology of the Montpellier snake (Malpolon monspessulanus) under natural conditions is poorly known. It is commonly accepted that, as in other colubrids, it lays its eggs under dry leaves (Naulleau, 1984) or in crevices in the ground (Hailey, 1982). Burger &amp; Zappalorti (1986), while noting that the reasons for nest site selection have not been studied in snakes, suggest predator avoidance and protection of eggs from inclement weather. Both factors may be extremely important for nest‐site selection in our study area, the Doñana National Park (37°7′, 36°48′ N; 6°12′, 6°30′ W) which is extremely dry, with hot summers and mild winters. Montpellier snakes lay their eggs in mid‐July, well into the summer (mean rainfall = 4°7 mm; average temperature = 22°28 °C, for June, July and August period). Additionally, densities of potential predators are also very high (Valverde, 1967). Consequently, selection of protected nest sites is likely to be extremely advantageous for this snake since both predation and desiccation of eggs will be reduced. As the sandy ground lacks natural crevices and holes, the use of dens of animals such as bee‐eater galleries (Alvarez, 1974) and rabbit warrens may be favoured.

Sheep Preference for Perennial Glandular‐haired and Eglandular Medicago Populations

Erect glandular‐haired Medicago species and hybrid populations have been developed that possess a high degree of resistance to the alfalfa weevil [Hypera postica (Gyllenhal)] and potato leafhopper [Empoasca fabae (Harris)]. Trials were conducted at the North Agronomy Farm, Manhattan, KS, in June and August 1986 to determine if erect glandular hairs on diverse perennial Medicago populations affect forage preference of sheep (Ovis aries). Glandular‐haired (+) and eglandular (−) populations were selected from each of the following: diploids M. prostrata Jacq. and M. glandulosa David (KS94) and tetraploids M. glutinosa Bieb. (KS108), M. sativa L. ✕ M. prostrata (KS159), and M. sativa ✕ M. glutinosa (KS160). Eglandular M. sativa ‘Riley’ (2n = 4x = 32) and M. sativa spp. caerulea (Less, ex Ledeb.) Schmal. (2n = 2x = 16) (MS2x) were included as controls. Four pairs of Suffolk wethers were allocated randomly among four replicates of Medicago populations in a cafeteria grazing trial. Sheep bites were counted 1 of every 5 min that grazing occurred. Pre‐ and postgrazing plant heights were measured. Populations differing by (+) or (−) showed significant differences for five of the 10 comparisons for the two grazing periods. The KS108(+), KS159(+), and KS160(+) entries were preferred to their corresponding eglandular populations in the June period. The KS108(+) and KS159(−) entries were preferred to their corresponding (−) and (+) entries, respectively, in the August period. Riley was significantly preferred over MS2x in the August period. Tetraploid entries had significantly higher initial plant height and were generally more preferred than diploid entries for both periods. For these populations, the presence of glandular hairs and their exudates did not negatively affect forage preference by sheep.

Forcing Mechanisms and Other Characteristics of Significant Summertime Precipitation

Satellite, radar, surface, and upper-air data from the June–August periods of 1982–83 are examined to determine the mechanisms, and their relative contributions, for producing warm-season precipitation in the United States. Only areas where rainfall equaled or exceeded 12.7 mm during the 24-h period ending at 1200 UTC were considered. Rainfall associated with extratropical cyclones accounted for about half of the warm-season precipitation. Most of the remaining precipitation was produced by mesoscale forcing mechanisms acting independently from the traveling extratropical cyclones. Nearly all the warm-season precipitation was convective; over 80% of the total was directly or indirectly associated with thunderstorms. Nearly three-fourths of the precipitation that occurred between the Rockies and the Mississippi Valley was nocturnal. Conversely, about three-fourths of the precipitation east of the Mississippi Valley fell during the daylight hours. During the 1983 July-August drought, the area of precipitation from extratropical cyclones was significantly smaller than the precipitation area during the corresponding period in 1982. The decrease was the result of a sharp drop in the frequency of cyclone events. Conversely, the frequency of mesoscale events and associated precipitation increased during the drought year. This difference in precipitation mode from one year to the next may help explain the large differences in numerical model forecasting skill from summer to summer. The large proportion of warm-season precipitation produced by mesescale forcing mechanisms suggests that further improvement in forecasting cyclonic storms and fronts will likely result in only limited increases in summertime quantitative precipitation forecast (QPF) skill. Moreover, the historically smaller values of warm-season QPF skill, relative to the cool-season levels, are likely to continue until operational numerical models can predict mesoscale convective systems as well as they predict extratropical cyclones and attendant fronts.

Gaseous and particulate air pollution in the san gabriel mountains of southern california

In order to assess concentrations and daily patterns of air pollutants at a mountainous site in the South Coast Air Basin, a study was undertaken in the San Dimas Experimental Forest of the San Gabriel Mountains between April 1985 and October 1985. Continuous monitoring of O 3, NO, NO 2, SO 2, total S compounds and light scattering coefficient was conducted. Particulate aerosols were collected twice a week and concentrations of nitrate, ammonium and sulfate in fine (< 2.5 μm diameter) and coarse (> 2.5 μm diameter) modes were determined. For the June–August period, when the levels of photochemical smog were the highest, monthly 24-h average concentrations of the pollutants were: O 3, about 200 μg m −3; NO 2, 40–75 μg m −3; NO, 1–5 μg m −3; and SO 2, 0.5–5 μgm −3. The concentrations of O 3 were about two times higher than in the neighboring stations of the South Coast Air Basin. O 3, SO 2 and total S concentrations peaked in the early afternoon, generally between 1500 and 1600 PST. Peak concentrations of NO occurred in the morning, generally between 1000 and 1100 PST. NO 2 concentrations typically peaked in the late afternoon between 1500 and 1800 PST, but occasionally (in 9 % of days) maximum NO 2 occurred in the morning, concurrently with the NO peaks. Daytime concentrations of the nitrate in fine aerosol fraction were generally between 100 and 600 nEq m −3, those of ammonium between 50 and 300 nEq m −3, and concentrations of sulfate between 60 and 250 nEq m −3. A 3-day denuder study showed that HNO 3can make up to 73 % of the total amount of total nitrate in the air. NO 2 was the most abundant N compound at Tan bark Flat (69–86% of the total amount of the monitored N compounds). Nitrate amounted to 9–15 %, HNO 3 to 4–11 %, ammonium to 3–9%, and NO to 1–2% of the total amount of the measured nitrogen compounds.

Biomass of the micronekton in Gulf Stream ring 82-B and environs: changes with time

Micronekton biomass was sampled in warm-core Gulf Stream ring 82-B (at ages 2, 4 and 6 months), the Slope Water, the Gulf Stream and the Sargasso Sea during three multi-ship cruises. There was no significant diel difference in the 0–1000 m integrated biomass for fishes or invertebrate micronekton in 24 paired day-night tows, and no evidence for diel vertical migration across the 1000 m level. Biomass showed a consistent upward shift at night; although it varied with hydrographic regime and sampling date, median biomass depth shift for invertebrates averaged 184 and 137 m for fishes. For total micronekton, median biomass depth ranged from 550 to 750 m by day and 300 to 600 m by night. Fish biomass was always centered deeper than 250 m, while the center of invertebrate biomass rose above that level in only one of 12 night tows. In April, ring-core biomass for fishes and invertebrates (2.2 and 11.9 cc m −2, respectively) was significantly lower than that for the high velocity region (3.6 and 19.8 cc m −2) or that for the Slope Water (4.7 and 20.8 cc m −2). By June, ring-core standing stocks had doubled while that for the high velocity region had been reduced to half of the April levels. No significant changes in Slope Water biomass occurred over the April–August period. Fluctuations in ring-core micronekton biomass were probably due to both in situ processes and advective exchange. On the average, invertebrate biomass was about 4 times that of fish biomass. Total micronekton was 20–30% of the macrozooplankton biomass in April and June, and 7–16% in August. Vertically, the invertebrate fraction overlapped the macrozooplankton more than did the fish fraction. Greater overlap of micronekton and macrozooplankton occurred at night.

Potential seed yield of white clover varieties

AbstractFifteen varieties of white clover were sown in order to assess the seed yielding ability of new and potential varieties and to examine those plant factors which affect seed yield. Counts were made on number of inflorescences m‐2, proportion of ripe inflorescences and other inflorescence and seed characters. The data were used to compute potential seed yields.Average potential seed yields were 276 and 76 kg ha‐1 in the first and second year, respectively. The decrease in the second year seed yields underlines the overriding effect of adverse weather conditions during the critical June to August period. The major effect was a reduction in the number of inflorescences produced, the number of florets per inflorescence and seeds per floret.Some of the new listed varieties have a significantly higher seed potential than SI00, e.g. Menna (+ 38%) and Olwen (+28%), and this should facilitate the production of adequate seed supplies of British bred varieties.

Phenology and Ecology of Some Trichoptera in a Low-Gradient Boreal Stream

Nine species of caddisflies (seven species of Leptoceridae, Helicopsyche borealis and Molanna flavicornis) were univoltine in a stream near Edmonton, Canada. Neureclipsis bimaculata was bivoltine at this site. No evidence of egg or adult diapause was seen among the ten numerically dominant species, although four species apparently overwintered as dormant larvae. No obvious increase in mortality was associated with overwintering. Emergence of the ten species occurred during the June to August period. Analysis of literature records of adult collections revealed significant relationships between date of first capture and latitude, and duration of the capture period against latitude for H. borealis and Oecetis inconspicua. Most of the species were found in association with macrophytes, especially Chara and Potamogeton richardsonii. Macrophytes were important as attachment sites for pupal cases, for dormant overwintering larvae, and for the filtering nets of the net-spinning species. Macrophytes may also be im...