摘要:

Abstract.1Resistance to desiccation and body size were studied in the drosophilid fliesZaprionus vittigerandZ.tuberculatus.2Populations in a hot dry low altitude area were compared with those in a nearby cooler wetter high altitude area in the north‐eastern Transvaal of South Africa, using laboratory strains established from these populations.3No between‐area differences were found for either body size or resistance to desiccation considered separately.4However, inZ.tuberculatus, regression analyses using strain mean values showed a strong positive correlation between the two characters amongst strains derived from low altitude populations but not amongst strains derived from high altitude populations.5It is concluded that differences of genetic organization have evolved between low and high altitude populations ofZ.tuberculutus.6From differences between species and sexes it is concluded that both body size and some unknown factor related to sex may influence resistance of desiccat

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1980.tb01155.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Abstract.1Seasonal reproductive development was investigated in four obligate fungivorous species,D.phalerataMeigen,D.transversaFallen,D.camerariaHaliday andD.confusaStaeger.2Samples of females taken from woodlands over a 2 year period were scored for reproductive status and fat content.3Populations ofD.phalerataandD.camerariamaintained in an outdoor insectary provided information on developmental time and adult mortality throughout the year.4Experiments in controlled environmental chambers gave percentage diapause curves against day length for all four species.5InD.phaleratathe influence of temperature and fungus upon diapause behaviour was also investigated.6InD.phaleratathe optimal strategy for reproductive development can vary from month to month. Maturation of females may be immediate, dependent upon a fungal cue or completely prevented.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1980.tb01156.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Abstract.1Details of a reintroduction of the swallowtail,Papilio machaon, to Wicken Fen are given.2The introduced population expanded at first, but crashed as a result of the 1976 drought. It then failed to recover and is probably now again extinct on the Fen.3The changes in the habitat and the status of the butterfly's food plant,Peucedanum palustre, caused by the drying out of the Fen are discussed, and it is concluded that there is no chance of reestablishing the butterfly permanently at Wicken, unless the Fen can be made wetter.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1980.tb01157.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Abstract.1The population dynamics ofBlepharidopterus angulatus(Heteroptera: Miridae), preying on the lime aphid, were investigated from 1965 to 1974. Numbers increased or remained stable until 1969, then declined, at least intermittently.K‐factor analysis showed that the key factor wask5+6(loss of adult females, eggs and newly‐hatched nymphs).2Detailed study of numbers and mortalities from 1968 to 1971 showed that loss of adult females was the largest part ofk5+6. Studies of flight activity showed most females probably emigrated from the trees before laying eggs, butk5+6was not related to aphid numbers at the time of peak migration. However, variation ink5+6depended on the length of time that aphid numbers remained favourable for egg‐laying.3Because of the consistently high emigration of adult females,B.anguhtusnumbers increased on average by only 10% when aphid numbers favoured egg‐laying. Nett emigration was usually high, probably because the trees were isolated or in rows, with few sources of immigrants to the South‐West (direction of prevailing wind). Since the population declined by 85% in years when aphids favoured egg‐laying for ≤ 20 days, recovery would be slow after a bad year. Since 1969, 1971 and 1973 were all bad years, this explains the intermittent decline inB.angulatusnumbers after 1969.4Simulation showed that neither increased numbers nor faster population growth ofB.angulatuswould enhance stability of predator and prey populations, but would lead to over‐exploitation of the latter. Given its low observed rate of increase, it is unlikely thatB.angulatuscould persist on lime at levels much above

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1980.tb01158.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Abstract.1The distribution of infestation levels of the coccidIceryu seychellarumon bushes ofScuevola taccuduand its population fluctuations over a 10 month period on Aldabra atoll show that individual plants ofS. taccadaexhibit differential susceptibility to attack.2Coccids on heavily and lightly infested bushes show no important differences in growth rate, fecundity or plant induced death rate. There were also no demonstrable differences in bush exposure, food quality (total and soluble nitrogen levels) or settlement behaviour of first instar larvae (crawlers).3Detailed examination ofIceryupopulations on individual leaf clusters showed that mortality caused by leaf fall is density dependent and can be avoided only if a large proportion of the population frequently moves from senescing to mature leaves. The proportion of the population required to move to younger leaves in order to complete development is greater in low densityZceryupopulations.4The effects of leaf fall are discussed with reference to the maintenance of differential susceptibility within the plant population.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1980.tb01159.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Abstract.1Ecological segregation was studied inAphaenogaster rudisEmery,Paratrechina melanderi(Wheeler) andPrenolepis imparis(Say), the three commonest surface‐foraging ants in a Maryland (U.S.A.) hardwood forest community.2P.imparisretreats from the surface during mid‐summer, but shows more cool‐season activity than do the other two species.P.melanderiis most active during the warmest months of the years.A.rudisis the most generalized of the three species in its seasonal activity pattern.3P.imparisis a highly aggressive species which forms large mobilizations at rich food sources.P.melanderiis a timid species which forms small mobilizations.A.rudisis intermediate in both respects.4Based on the results of baiting trials,P.imparisshows an apparent preference for protein‐fat food,P.melanderiprefers carbohydrate food, andA.rudisexhibits no significant preference for either fclod type.5As a result of its extended seasonal activity, weak circadian periodicity, and lack of food specialization,A.rudishas the broadest annual niche of the three species studied.6The unusual seasonal activity patternof P.imparisresults in a relatively low degree of annual niche overlap between this species and either of the other two. Overlap betweenA.rudisandP.melanderiis substantially higher.7Experimental manipulations confirm that rates of resource removal by a behaviourally subordinate species(Amdis)are reduced in the presence of a dominant species(P.imparis).8Persistence of these three widespread, abundant, relatively generalized ant species in local sympatry may in part reflect their differential success in: (a) finding food, (b) defending food, and (c) handling food items of differen

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1980.tb01160.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Abstract.1The temporal and spatial distribution of parasitism inEpinotia tedellawas investigated within two spruce stands.2Most eggs were laid by the host female early in the season. The parasitoid,Pimplopterus dubius, was subjected to a temporal stress, and it also exhibited a greater oviposition rate early in its life. The temporal distribution of attack frequencies byP.dubiusandApanteles tedellaeshowed a good adaptation to the phenology of the host.3The spatial distribution of flight activity indicated a preference to exposed sub‐habitats byP.dubiusand to dark and sheltered sub‐habitats byA.tedellae.The distribution of host larvae showed an aggregation in the lower and central parts of the canopy, and so did the attacks byA.tedellae— even more pronounced. The attacks byP.dubiusshowed a slightly inverse aggregation pattern. Apparently, the distribution of attacks was caused by preference to physical conditions, rather than local host densities.4The decreasing log. area of discovery on increasing log. parasitoid density is obviously a ‘pseudo‐interference’ phenomenon caused by the aggregation ofA.tedellae, and temporal asynchrony inP.dubius.5P.dubiusdominated in young stands and its importance decreased with increasing age of the stands. The importance ofA.tedellaewas greatest in stands between 20 and 40 years old, and it dominated in those stands that were especially dense and dark, due to absen

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1980.tb01161.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Abstract.1Interactions between insect sex attractant traps are of ecological interest in themselves, but may cause problems in field experiments in which attractants, or control measures, are compared quantitatively.2Some of these problems are solved by experimental designs based on the Latin Square.3The applicability of the designs to research involving comparison of attractants, effectiveness of control measures and attractant trap interactions is discussed, and examples are given with field data.4Efficiencies of different designs are compared using data from fifteen experiments.5Disadvantages and extensions of the design are discussed.6Latin Square designs are simple, practical, and usually more efficient than other designs.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1980.tb01162.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Abstract.1Ptinella apteraandPtinella errabundaoften coexist where their distributions overlap.2The ecological requirements ofP.apteraandP.errabundaare similar. Both are generalized mycetophages restricted to the same subcortical habitat of trees in a particular state of decay. Relative humidity appears important in determining habitat suitability for both species, neither of which survived in laboratory regimes below approximately 100% relative humidity.3In laboratory studies the beetles differed in their response to temperature. Recorded maxima for activity and rate of increase were at higher temperatures forP.apterathanfor Perrabunda.4Temperatures which ‘Ptinellawere exposed to in the laboratory occur in natural conditions under bark. Their effects on the species’ distributions are considered.5The differential temperature adaptations ofP.apteraandP.errabundawere probably evolved in allopatry, in response to different environmental conditions. In view of this, it is unreasonable to infer past interspecies competition from these niche differences.6The niche difference between coexistingPtinellaspecies is discussed in the light of current ideas concerning the relative importance of competition and other factors in natural communit

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1980.tb01163.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY