bluuebunny/crossref_metadata_2025_split huggingface dataset:
Duration of the Aquatic Stages of Povilla adusta Navás (Ephemeroptera: Polymitarcidae)
Authors: Corbet Philip S. 
Published: July 2009

SummaryThe duration of the aquatic stages of the mayfly, Povilla adusta Navás, in Lake Victoria, Uganda, has been determined by analysing larval samples from the stomachs of an insectivorous fish, Mormyrus kannume Forsk., and by culturing eggs in vitro. Emergence shows a well-defined lunar rhythm and, since adults live for only about one hour, duration of the aquatic stages must be an integral number of lunar months. Results indicate that a generation is usually completed in four or five months. Approximately the first two weeks of this period are spent in the egg.The periodicity of reproduction imposes a feeding rhythm on certain species of fish in Lake Victoria. Some biological implications of the need for synchronisation are briefly discussed.
The Genus Musa Linn. and its Role in the Breeding of Aedes (Stegomyia) simpsoni (Theo.) on the Kenya Coast
Authors: Teesdale C. 
Published: July 2009

SummaryThe varieties of the banana plant (Musa) on the Kenya coast, with particular reference to Aëdes simpsoni (Theo.), a species concerned with the transmission of yellow fever in East Africa, are described, and the species of mosquito larvae found in their leaf axils are recorded. A. simpsoni was virtually the only species present.Details are given of the proportion of leaf axils that contain water and the percentage of these that produce larvae. Breeding was found to take place in all varieties, but to a much lesser extent in that known as Kibungala than in the others. Although there was often more water in the lower and upper axils than in the middle ones they produced less larvae individually than did the latter. Larvae were also found in old axils at the base of the stems in spite of the fact that these sites seldom appear to provide direct access for an ovipositing mosquito. Water was present throughout the year in the upper axils only.It was found that the water content of axils varied from day to day and from morning to evening during dry periods and that the axils were often apparently dry for days at a time although the larvae were able to survive. It is suggested that the larvae are able to survive in the water film at the base of the axils, but that such unfavourable conditions may account for the retarded growth that has been observed.The relationship between water content and number of larvae per axil is discussed, and the conclusion is reached that unless all measurements of water content for all varieties are made simultaneously each day, a comparison of average water content becomes impossible, and therefore no connection can be established from the data so far available.
Observations on the Behaviour of Culicine Mosquitos in African Huts
Authors: Phipps John 
Published: July 2009

SummaryObservations on the behaviour of Culex pipiens fatigans Wied. were made in 24 huts built and occupied by Africans on a sisal estate near Tanga, Tanganyika Territory. Catches were made in four huts each day, an exit trap being fixed on the window from 2 p.m. to 6 p.m. (evening trap) and replaced by another from 6 p.m. to 8 a.m. next day (morning trap), when a spray catch was made of the mosquitos still in the hut. Each hut was used only once a week, for 31 weeks, from December 1952 to July 1953. The females caught were sorted according to the stage of the gonotrophic cycle, as judged by external examination. The stages used were: I, no blood, no visible ovaries; II, stomach full of blood, ovaries small; V, little or no blood, ovaries fully developed; III and IV, intermediate between II and V.An analysis of variance was performed on the results. Catches of both sexes showed a significant variation with time, which was not, however, correlated with rainfall. Significantly different numbers were taken in the traps and in the huts. Females were significantly most numerous in the hut catch, and males in the morning trap, the former result suggesting that most females spend more than one day in a hut. There were significant differences between the numbers of females in the different stages of the gonotrophic cycle, stages I and II together accounting for 80 per cent, of all females caught. The high proportion of stage I is attributed to delay between emergence and feeding, and of stage II to the taking of more than one meal during the gonotrophic cycle, later meals obscuring the state of ovarian development. There were significant differences between huts as regards the numbers of females caught, but not as regards males, and it is concluded that this is due to variations in the attractiveness of the inhabitants of the huts.Females in stage I were most numerous in the morning trap, those in stages II–IV were taken only rarely in traps, but there was no significant difference between numbers of stage V caught in huts and in the two window traps. These results arse attributed to restlessness in both hungry and gravid females, and sluggishness in fed ones. All stages except III were significantly more numerous in some weeks than in others and this might be due to variations in either rate of reproduction, or rate of loss of mosquitos from huts. There were significant variations in behaviour in different weeks. For females, this is attributed to changes in the proportions of the stages with time and the dependence of behaviour on stage. For males, there is some evidence of a relation between behaviour and humidity outside the hut. For females, the distribution of stages between different places of capture changes with time, stages II and III being most consistently associated with hut catches, while the most variable behaviour is shown by stage V.The necessity for behaviour studies on mosquitos in the field is pointed out, especially in relation to field trials of residual insecticides.
Method for Breeding, Handling and Sexing Adults of Drosophila melanogaster Mg. as a Test Insect for Bioassay
Authors: Gerolt P. 
Published: July 2009

SummaryA method is described by which a continuous supply may be produced, efficiently, of large numbers of adults of Drosophila melanogaster Mg. of known age and sex for microbioassay tests.Equal numbers of male and female flies were introduced into breeding jars containing a nutrient medium and maintained at 24–25°C. and 60–80 per cent, relative humidity. They were removed ten days later, just before the emergence of their progeny.It was found that the physical conditions in the culture jars exerted an appreciable influence on several aspects of the breeding of Drosophila. Thus, in trials in which the surface of the nutrient medium was flat and unbroken, with a pad of cotton-wool laid on it to provide suitable sites for pupation, and with or without a layer of cotton-wool beneath it, or in which the medium was broken with irregular lumps, laid on a layer of cotton-wool and arranged with a space, filled with cotton-wool, at the centre, the best results were obtained with the last modification.Under these conditions, emergence of adults began earlier and reached its peak earlier, a most constant sex-ratio and a higher number of progeny per female, and consequently a higher yield of flies per culture jar, were obtained.A special device, which takes advantage of the positive phototropism of the flies emerging from a group of culture jars enclosed in a darkened box with an exit funnel leading into a collecting jar, made it possible, by daily replacement of the collecting jar, to remove practically all newly emerged flies within 24 hours, so that the known age of any batch is accurate within the limit of one day.Male flies have been found to be twice as susceptible as females and give a greater response to differences in dosage of toxicant. For this reason male flies only are to be preferred for use in bioassay experiments.Using another device, the flies were therefore sexed, and the required number of batches of males collected. This device consists of a glass-covered container through which a gentle continuous stream of CO2/air is passed over the flies, which have already been anaesthetised with CO2. The male flies are taken up individually with a small aspirator and passed direct into test tubes where they are collected in batches.
The Effect of Obstructive Clearing on Glossina palpalis (R.-D.)
Authors: Nash T. A. M. , Steiner J. O. 
Published: July 2009

SummaryAn experiment has been undertaken in Northern Nigeria to ascertain whether the felling of the trees forming the overhead canopy and the deliberate blocking, with trash, of the stream-bed to obstruct the tsetse's flight-line, would result in the eradication of Glossina palpalis (R.-D.).Obstructive clearing was employed on approximately 3¾ miles of stream. The results suggest that, provided the experimental reaches are adequately isolated, obstructive clearing does lead to the eradication of G. palpalis.It is noteworthy that if, owing to inadequate isolation, the cleared stream becomes re-infested in the rains, conditions for at least the first two dry seasons are so unfavourable that flies cannot persist.The immediate effect of obstructive clearing is to increase greatly the hunger of the few surviving flies.Records suggest that obstructive clearing leads to a considerable reduction in the number of human hosts visiting uninhabited parts of the stream, presumably because of the destruction of forest produce. The duiker (Sylvicapra and Cephalophus) population also becomes greatly reduced, especially in the vicinity of hamlets. The hunger observed in the surviving fly population may therefore be in part due to an actual reduction in the number of hosts, as well as to the altered environment, which prevents free movement, under shade, of the hungry tsetse that is searching for food; instead, the tsetse is forced out into the open, where the climate in the dry season is intolerable, and presumably the unsuccessful fly rapidly succumbs from water-loss.The effect of obstructive clearing on the vegetation is as follows. Within a few weeks the mound of trash is overgrown with creepers, Mucuna pruriens becoming dominant. In the first year's heavy rains the mound of trash tends to sink down in the stream-bed; on larger streams, spates do some temporary damage to the creeper growth and gaps may appear in the obstruction. The impression gained is that the blockage will persist for many years on small tributaries, but will disintegrate within a few years on larger streams. In very hilly country, with a rapid run off, the obstruction is likely to be displaced. In perennial streams of the type dealt with, the annual fires make only small inroads into the obstruction.The technique evolved for the obstructive clearing of streams is described. The cost of this method worked out at 390 man days per mile, which is about half the cost of the present methods.Should large-scale undertakings in the field confirm the efficacy of this new method, the biggest saving will be the elimination of the present necessity to re-slash streams that have been partially cleared. Observations will be continued to ascertain how long it will be before the vegetation again becomes suitable for G. palpalis.
An Investigation into the Effect of Cultural Conditions on Populations of the Vectors of Virus Diseases of Cacao in Ghana with an Evaluation of seasonal Population Trends
Authors: Cornwell P. B. 
Published: July 2009

SummaryA comparison is made of the populations of mealybugs, ants, predators and parasites on cacao growing in dense secondary bush and under well-cultivated conditions in Ghana, West Africa. The percentage of cacao trees infested (termed the infestation rate), the number of colonies and the populations of the vectors were similar under the two cultural conditions. Populations of ants of the genus Crematogaster and of COCCINELLIDAE were higher in bush areas than in cultivated ones. Populations of ants of the genus Pheidole, though smaller than those of Crematogaster, were greater in areas of well-maintained cacao.Correlations of infestation rates and populations were compared under the two cultural conditions for mealybugs, ants, predators and parasites. The field data showed an exponential relationship between these factors, which was rendered linear by suitable transformations. The correlation of mealybug populations with infestation rate and with populations of parasites and predators was equally high in both habitats. The correlation of mealybug populations with those of Crematogaster was closer in the bush than in well-maintained cacao, but the implications of this are not fully understood.There was a higher infestation rate of cacao during the first three months of the year. In contrast with previous work, the present survey has demonstrated significant changes in the vector population during the year, of a five- or six-fold order. These seasonal changes are based on mean mealybug populations per infested tree, and were largely the result of changes in the numbers of colonies; populations showed a decline during the first six months of the year and then rose to a maximum during October–November. The data suggest that these trends may be brought about largely by changes in the abundance of predators and parasites.
A Study of the Blackfly, Simulium ornatum Mg. (Diptera), with particular Reference to its Activity on Grazing Cattle
Authors: Davies L. 
Published: July 2009

SummarySamples of aquatic stages, taken from a small lowland stream near Durham, England, showed that the blackfly, Simulium ornatum Mg., emerged in quantity from April to October (7 months) and that oviposition took place between May and October. Oviposition was confined to the period between sunset and dusk.Flies emerging in the early summer of 1952 were smaller than those emerging in the spring and late summer of that year.S. ornatum landed on cattle from dawn to dusk, with usually a small peak 2–4 hrs. after dawn, and a large peak between sunset and dusk on warm, sunny days. On cool, cloudy days the number of flies landing showed irregular fluctuations throughout the day.The number of flies landing on untethered cattle was not markedly dependent on air temperature or saturation deficiency. Winds of over 5 m.p.h. markedly decreased or inhibited landing activity.On average about 70 per cent, of all blackflies landing spent less than 10 min. on cattle after landing, and this interval sometimes decreased as the total number of flies landing per unit time increased.Of the flies which landed, some 8 to 25 per cent, were calculated to bite the cow, and the proportion which bit varied significantly from day to day. The number of bites sustained by cattle in the district appeared to cause no ill-effect, apart from the formation of scar tissue in the navel region where most bites were inflicted.
The Cumulative Toxicity of Diniteo-O-cresol applied in Small Doses to Locusts
Authors: MacCuaig R. D. , Sawyer K. F. 
Published: July 2009

SummaryBy the method of attacking flying swarms of locusts with insecticides sprayed directly into the swarm by relays of light aircraft, a proportion of the swarm receives a sub-lethal dose from each sortie. For successful operation it is essential that a substantial contribution to the final mortality should be produced by the accumulation of these sub-lethal doses on individual insects over a period of time. The object of the present experiments was to determine whether such doses applied at intervals are wholly additive in their effects. The poison used was dinitro-o-cresol (Mk. IV DNC solution) and to shorten the experimental procedure, the locusts, Schistocerca gregaria (Forsk.) and Locusta migratoria migratorioides (R. & F.), were dosed by means of a single drop of poison applied to the ventral surface of the abdomen by a micro-drop syringe.When locusts are given regular daily doses of DNC the doses are not wholly cumulative in their effect. After the second or third day the lethal effect of each dose becomes steadily less, and after the fourth or fifth day it tends to zero, representing a steady state in which the rates of application and loss of insecticidal activity in the survivors are equal.When the dose is applied in two halves with various time intervals between them, the cumulative effect during the first 24 hours is less in S. gregaria than in L. migratoria. In the latter species it is possible that sensitisation occurs. After three days, the first half-dose has fallen to an estimated 20 per cent, of its initial effectiveness in each species.These two species are equally susceptible to a single dose expressed as μg. DNC/g. body weight. The females are more resistant than the males to daily doses (relative susceptibility in S. gregaria, 1·54) but probably not to single doses (relative susceptibility, 1·09).Resistance to a daily dose correlates roughly with resistance to a single dose, the total dose required to produce 50 per cent, mortality in four days being about twice the LD50 for a single dose.If flight activity does not materially alter the present results, it is evident that the non-cumulative effects of sub-lethal doses could cause a serious loss in the efficiency of an air-spray operation if it were unduly prolonged. Thus a quantity of insecticide sufficient to kill over 99 per cent, of the locusts if applied as a single dose would kill less than 40 per cent, if the application were spread over four days.
Studies on Wheat Bulb Fly (Leptohylemyia coarctata (Fall.)). IV.—The Distribution of Damage in England and Wales in 1953
Authors: Gough H. C. 
Published: July 2009

SummaryIt is estimated that in 1953, as a result of attack by Wheat Bulb Fly, Leptohylemyia coarctata (Fall.), 59,000 acres of wheat were re-drilled and 58,000 acres were patched with spring-sown wheat; another 85,000 acres were affected without any action being taken by the farmer. The cost of new seed and the reduction of yield of spring wheat as compared with winter wheat represent a minimum financial loss of about £1,200,000. With the aid of maps it is shown that the distribution of damage is similar to the distribution of wheat and to the area with less than 30 in., rainfall annually. In districts where over 5 per cent. of the combined crops and grass acreage is in potatoes, there is a tendency for the amount of damage by Wheat Bulb Fly to increase with increasing potato acreage.It is tentatively suggested on circumstantial evidence that high rainfall on the west side of the country is partly responsible for the absence there of damage by Wheat Bulb Fly. Many of the variations in the distribution of damage on the eastern side of the country could be accounted for by differences in cropping.In Scotland, the distribution of the fly is also confined to the eastern side. There are a few records of the fly in the Republic of Ireland.
The seasonal incidence of biting flies (Diptera) in Rwenzori National Park and Kigezi Game Reserve, Uganda
Authors: Kangwagye T. N. 
Published: July 2009

AbstractBetween January 1965 and August 1967 49 species of biting flies were caught in Langridge and Fredeen traps and from bait animals in western Uganda. Catches were recorded daily, and monthly catches (geometricmeans) of the species most frequent on bullocks were plotted as percentages of the year's catch. Haematobia minuta (Bez.) was the only species to show a unimodal peak; this is attributed to maintenance of soil conditions suitable for the larvae during the short rains (September-November). Bimodal peaks are shown by Haematopota brunnescens Ric, H. patellicorne (End.),Tabanus par Wlk., Stomoxys inornata Grünb., S. nigra nigra Macq. and Haematobosca squalida (Grünb.) (adversely affected by severe dry conditions), by T. taeniola P. de B. and T. thoracinus P. de B. (emergence from pupae coincides with the beginning of the rainy seasons (March-May and September-November)), by Stomoxys omega Newst. and Haematobiaspinigera Mall, (minimum numbers in the wet months September-October), and by species of Haematopota, Tabanus, Chrysops, Stomoxys and Haematobosca(breeding occurs in the rainy seasons). Ill defined cycles are shown by Chrysops distinctipennis Aust, C. longicornis Macq., S.ochrosoma Speiser and females of S. calcitrans (L.) ; Glossina fuscipesNewst., G. fuscipleuris Aust. and G. pallidipes Aust. showed minimum numbers in September-October.
The range of attraction of birds as baits for Some West African mosquitoes (Diptera, Culicidae)
Authors: Gillies M. T. , Wilkes T. J. 
Published: July 2009

AbstractThe long range orientation of West African mosquitoes to birds was studied using ramp-traps set up 3–23 m from the bait. The baits comprised chickens, ducks, pigeons and the carbon dioxide equivalent of the chickens. From the pattern of convergence of mosquitoes to the baits, it was shown that Anopheles melas Theo. and Culex thalassius Theo. were orienting to all the bird-baits from distances of at least seven metres. Responses to carbon dioxide were only apparent at a distance of three metres indicating the greater range of effect of the chickens over their carbon dioxide equivalent. Mosquitoes of the largely bird-biting C. decens group showed no long range response to any bait, even though they were entering pigeon-baited traps and to a limited extent feeding on the birds. Catches of A. melas in bird-baited traps were larger at the foot of a tall tree than in the foliage at 5·33 m; for Culex spp. the converse was true. Catches of Culex at 5·33 m outside the tree were smaller than within the foliage.
Effects of light-trap design and illumination on samples of moths in an English woodland
Authors: Taylor L. R. , French R. A. 
Published: July 2009

AbstractOperated in sheltered woodland, the samples obtained by Rothamsted tungsten-filament and Robinson mercury-vapour traps are best described by a spatial model different from that used in a site exposed to wind. Differences between the proportions of Noctuidae and Geometridae were accountable to differences in height of flight. The Rothamsted traps gave more consistent samples than the Robinson traps and averaged about onequarter the number of moths.
Life-cycle variation ofMyzus persicae(Sulz.) (Hom., Aphididae) in different parts of the world, in relation to genotype and environment
Authors: Blackman R. L. 
Published: July 2009

AbstractLife-cycle variation, involving alternative methods of overwintering (holocycly and anholocycly), is found in many important pest aphids, and may have considerable ecological, genetic and economic significance. The occurrence of life-cycle variation in Myzus persicae (Sulz.) in different parts of the world is reviewed. The holocycle ofM. persicae, with sexual reproduction and overwintering of eggs on Prunus, occurs in the temperate regions of every continent, and although anholocycly is widespread in warm climates there are indications that the potential for sexual reproduction may be retained throughout the whole range of the species. The environmental factors involved in the determination of sexual morphs are considered. Photoperiodism provides the timing mechanism for sexual morph production, and the photoperiodic response is probably tuned to different regional conditions and buffered against other environmental variables within certain limits. The only other environmental factor clearly implicated in sexual morph production is temperature, and an attempt is made to correlate the global pattern of life-cycle variation inM. persicaewith temperature differences between regions, by dividing the world into six zones delimited by selected isotherms. The overall pattern of life-cycle variation can be explained largely on the basis of climatic differences between zones, and the effects of these differences on gene and genotype frequencies within the species. Clones of androcyclic character seem to be widespread and, although genetically isolated anholocyclic biotypes undoubtedly exist, androcyclic clones could be the principal source of parthenogenetic overwinterers in all parts of the world where life-cycle differences exist within populations.