摘要:

Abstract.1The species number, the abundance per species and the body length of arthropods foraging within the crowns of an over‐storey rainforest tree from Australia,Argyrodendron actinophyllum(Sterculiaceae), were investigated by interception trap sampling and restricted canopy fogging. Emphasis was placed upon the interpretation of trap data. Arthropods were trapped continuously day and night, over a 2‐year period and the final analyses examined the attributes of 759 species which represented 20,500 individuals.2The proportion of‘rare’species (Le. collected once) intercepted was high (35.7%), although lower than in other similar rainforest surveys. Neither the α log‐series nor the log‐normal distribution could be fitted to the relationship between number of species and number of individuals, since the number of rare species was much higher than predicted and the mode of the distribution could not be identified. The proportion of rare species was higher in fogging collections (452%) than in trap collections.3The data are compared with a study of Bornean arboreal beetles, obtained by fogging trees during a single sampling event. Several patterns were common to both data sets. However, the three‐dimensional plot of the variables describing the structure of the arthropod community showed a notably rougher surface than in the case of Bornean beetles.4Although several factors may complicate the interpretation of the three‐dimensional plots, long‐term and continuous sampling may alter our perception of complex arthropod communities. This methodology is imperative for a proper understanding of arthropod community structu

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00232.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1We tested switching behaviour in four species of aphidiid parasitoids, using a two‐aphid experimental system consisting of second‐instar nymphs of pea aphid (Acyrthosiphon pisum(Harris)) and alfalfa aphid (Macrosiphum creeliiDavis) feeding on broad beans in the laboratory.2Aphidius erviHaliday,A.pisivorusSmith,A.smithiSharma&Subba Rao, andPram pequodorumViereck showed an innate preference for pea aphid when both host species were provided in equal numbers.3Wasps encountered both aphid species equally but differed in their acceptance of alfalfa aphid. Females ofA.pisivorusandP.pequodorumaccepted alfalfa aphids when few pea aphids were available, butA. smithialways concentrated attacks on pea aphid.Aphidius ervisuper‐parasitized an increasing proportion of pea aphids as their availability declined.4Switching to the alfalfa aphid occurred inA.erviandP.pequodorum(but not inA.pisivorusandA.smithi) under the condition of a 1:3 ratio of pea aphids:alfalfa aphids. Wasps did not switch when more pea aphids than alfalfa aphids were provided (3:1 ratio).5Alfalfa aphids were more likely than pea aphids to escape from parasitoid attack.6Switching to the most abundant host may not be adaptive in these four species of aphid parasitoids. A foraging wasp incurs a potentially higher cost in lost opportunity time when attacking (and failing to oviposit in) alfalfa aphids. In addition, alfalfa aphids may have lower host quality than pea aphids, a difference that could influence offspring fi

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00233.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1It is shown that the size distribution and degree of overlap between individual queens of the two forms ofMyrmica ruginodis, microgyna and macrogyna, is exactly the same in southern England as was originally described from Scotland.2Distinguishing colonies of the two forms is not as easy as distinguishing between individuals, both types can be polygynous and approximately 25% of colonies contain a mixture of queens.3Males of the two forms can be distinguished solely on the basis of size and, in general, macrogyna colonies produce larger males, workers and gynes than microgyna colonies. There is little correlation between the sizes of males, workers and gynes in colonies within the macrogyna and microgyna groups.4If the two forms are separate species and mixing is a parasitic association (as suggested elsewhere), then there should be breeding isolation between the forms. This is tested by examining data from nine mating‐swarms.5All the swarms contain a significant proportion of the microgyna form. There is no evidence of assortative mating, although larger males are more likely to get a mate than smaller ones. This behaviour, combined with the possibility that microgynes mate near to the nest, might prevent complete mixing during mating.6The status of the forms is discussed. Besides the possibility of a‘pre‐parasitic’relationship it is suggested that the forms might represent a polymorphism, present in all populations, the balance between them being the result of selection determined by local environmental

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00234.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1Butterflies ofBattus philenorwere tested for their preferences for nectar sugars and amino acids in an outdoor cage experiment.2The butterflies clearly preferred both sucrose and fructose over glucose. They also preferred sucrose over fructose.3No other preferences were found to be statistically significant, although male butterflies tended to prefer a plain sugar solution over a sugar solution containing a mixture of amino acids: females consumed both of these solutions in almost equal proportions.4The results are discussed with respect to nectar composition of butterfly pollinated flowers, flower preferences, physiological and reproductive aspects of butterflies.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00235.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1When freshly eclosed females of the primitively eusocial waspRopalidia marginata(Lep.) are isolated, only about 50% of them build nests and lay eggs thereby suggesting a pre‐imaginal biasing of caste.2Wasps that lay eggs take a very variable amount of time after eclosion to start doing so.3Females eclosing from nests where larvae are fed at a relatively higher rate are more likely to become egg‐layers and are likely to take less time after eclosion to begin to lay eggs.4Thus, both forms of pre‐imaginal biasing of caste, namely, differences in egg laying capacity and differences in the time taken to attain reproductive maturity, appear to be influenced by larval nutr

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00236.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1New Zealand was colonized by the German wasp,Vespula germanica(F.), in the 1940s and it subsequently became established throughout the country. The common wasp,V.vulgaris(L), colonized in the late 1970s and is still spreading.2The common wasp has replaced the German wasp in some habitats in New Zealand. Samples from a nationwide postal survey indicate that the common wasp is now the more abundant species in honeydew beech forests (Nothofagusspp.), and to a lesser extent in other native forests. The German wasp is still the more abundant wasp in rural areas (excluding forest). The two species are at present co‐dominant in urban areas, although this may be a transient phase.3In honeydew beech forest the two species show different foraging patterns that provide the potential for local coexistence. Although both species are generalist feeders, the German wasp is more commonly found foraging for protein amongst the forest litter, whereas the common wasp forages more on shrubs and tree saplings. Despite this difference, the common wasp can still replace the German wasp in honeydew beech forest within a few years of invasion.4In honeydew beech forests in which the German wasp is the more abundant species it dominates honeydew trunks (sugar resource), whereas the common wasp dominates honeydew trunks in areas where it is the more abundant species. The change from German to common wasp domination of honeydew trunks is more rapid than the change in dominance in other microhabitats. Aggressive interactions may be taking place on this high quality, potentially defensible sugar resourc

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00237.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1The population dynamics of a natural population ofSympetrum danae(Sulzer) were studied, by means of a mark—release—recapture method, to find indications of dispersal by mature adults. Additional information on orientation and the influence of phenotype (including age), density and weather was obtained by observations under natural conditions and in a large outdoor field cage.280% of all mature adults caught around the natural pond were estimated to be immigrants. Considerable immigration was confirmed by the abdomen length of unmarked matures which did not accord with that expected from the locally emerged population. Total numbers captured and the minimum number known to be alive fell sharply at the time when most individuals were mature. At the same time, new matures continued to enter and disappear from the study area at an increasing rate.3Dispersive behaviour (escape flights) in the field enclosure was primarily age dependent in both sexes: it occurred from an age of 25–30 days onwards. This coincides with the time‐lag between the emergence peak and increased dispersal in the field. Secondary effects on escape flights suggested that males tended to abandon low density areas.4Males flew relatively more southward than

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00238.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1Point estimates of parasitoid behaviour indicated that braconid parasitoids of the bark beetle,Leperisinus varius, spend 70% of their host searching time stationary on the bark surface, in sharp contrast to the chalcidoid parasitoids which spend 60–70% of their host searching time moving across the bark surface.2Aggressive encounters between searching parasitoids are common and the data suggest that they do not occur at random.3The chalcidoid parasitoids,Cheiropachus quadrumandEurytoma morio, are more frequently involved in aggressive encounters than expected and can displace ovipositing individuals of other species.4Attack rates for the parasitoids were estimated to vary from two hosts per day for the braconidCoeloides filiformisto four hosts per day forE.morio, and net reproductive rates vaned from 6.3 forC.filiformisto 0.8 forCoeloides melanotus.5These data suggest that while all parasitoids of the scolytid can act as primary parasitoids, at least some of the chalcidoid parasitoids are facultative cleptoparasitoids and should be avoided in classical biological control introduction

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00239.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1A case study is presented of the autumn migration of the brown planthopper,Nilaparvata lugens(Stål), in the area of Nanjing in the People's Republic of China. The study was made using a high frequency (8 mm wavelength) radar and a net suspended from a kytoon.2The observations confirmed that long‐distance return migrations occur in China in mid and late September, withN.lugensbeing carried on the prevailing north‐easterly wind towards the autumn infestation and overwintering areas of the species.3After mass take‐off in the late afternoon or at dusk, the migrants flew for several hours during the evening, often in a dense layer which formed at heights between about 400 and 1000m above ground. These layers often had well‐defined ceilings corresponding to an air temperature of about 16°C. The migration height was above the top of the surface temperature inversion, i.e. the migrants did not fly at the height of the warmest air.4The dense layer concentrations overflying the radar were backtracked to source areas up to 240 km away in the north‐east of Jiangsu Province. Planthoppers observed emigrating from the Nanjing area would reach areas in south Anhui Province or north Jiangxi Province if they flew for 12 h.5There was a second period of mass take‐off at dawn. Insect layers sometimes formed but did not last longer than 1–2h.6The present results were strikingly different from those previously observed in the dry season in the Philippines, where migratory flight durations were largely confined to periods of about 30min at dusk and dawn.7Our observations are discussed in relation to the equator‐wards return migrations undertaken in autumn by other insect species, and the importance of these migrations for the maintenance of long‐flying genotypes in the overwintering popula

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00240.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1In European and American apple orchards the insect species richness, calculated from our own, and published data, varied widely (30–940 species). The dominance of insect orders was similar to that found in natural communities.2To test the predictions of the‘resource diversity hypothesis’(RDH) and the‘intermediate disturbance hypothesis’(IDH) of insect diversity, we analysed the simultaneous impact of vegetational diversity and intensity of orchard management practice on the species richness of characteristic insect categories in six types of apple stands, over 5 years, in Hungary.3The more diverse was the vegetation adjacent to the orchard and the less intensively was the orchard managed, the greater was the total insect species richness, supporting both hypotheses.4The number of agricultural pest species found in the apple orchards depended above all on the diversity of adjacent agricultural vegetation, supporting only the RDH.5The species richness of specialized apple pests was limited only by the intensity of pest control, supporting only the IDH.6Within the category of generalist natural enemies species richness mainly varied with the diversity of adjacent vegetation, supporting the RDH.7The aeroentomofauna constituted a surprisingly high percentage (>50%) for both total species and agricultural pests, but was poorly represented within the natural enemies category, and absent from the specific apple pest category.8A general conclusion is that the number of insect species in perennial orchard‐systems within agricultural areas is determined primarily by the regional extra‐orchard vegetational diversity and secondly by the degree of local intra‐orchard disturbances and plant diversity. Consequently, at the community level the predictions of both hypotheses can be simultaneously valid at different spatial scales and are not mutually exclusive. However, within the community, at the level of the different insect categories studied here, only one of the hypotheses pro

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00241.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY