摘要:

Abstract.1. A population ofCalopteryx aequabilisSay was sampled daily on a tributary of Canard River, Kings County, Nova Scotia, for the entire flight season in 1983 (29 May to 13 August), using capture–mark–recapture techniques.2. 2701 sightings of 678 individuals were obtained along a 635 m segment of the stream. A maximum daily count of 174 imagines was reached on 11 June, after which the population gradually declined.3. More females than males were marked but sexually mature males outnumbered females at the water on all but four days.4. Immigration rather than local emergence accounted for a large proportion of the population after 20 June.5. Females were consistently vagile; males were site–specific but occasionally moved long distances between captures.6. Males and females first marked as tenerals became reproductively mature after about 5 days.7. We experimentally increased female density on a partially isolated section of the study stream to see how increased female numbers affected the demographics and movement patterns of the population.8. Residence times for introduced and resident females were similar. In contrast, during a similar introduction of males a year earlier, most introduced males disappeared quickly.9. Males decreased the distance they travelled daily between captures, their total distance travelled and their range following the introduction, and females showed a tendency (not statistically significant) toward increased movements and dispersal, as pred

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1990.tb00792.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1990.tb00793.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.1. The hypothesis that the migratory tendency of macropters is correlated with proportion macropterous in wing‐polymorphic insects is tested by comparing the migration of macropters of three species of waterstriders (Heteroptera, Gerridae) under natural conditions.2. Migration of marked individuals among four permanent and seventeen ephemeral water bodies was recorded between 1 April 1986 and 2 June 1987, within an area of approximately 2 km2.3. The proportion of macropters migrating was significantly lower forG.buenoiKirkaldy than forL.dissortisDrake and Harris andG.comatusDrake and Hottes. Similar results were obtained in. comparisons of proportions captured on ephemeral sites.4. Distances measured in this study appear to be small relative to the migratory capacity of all of the species, and migration distance did not differ significantly among species. All species migrated primarily in early spring, and differences among species were most apparent at this time.5. The observed differences among species combined with the results of a similar study of macropters from the primarily apterous species,G.remigisSay, support the initial hypothesis. The implications of this for our understanding of the evolution and maintenance of wing polymorphisms are discusse

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1990.tb00794.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.1. Weekly samples of Malaise trapped Coleoptera from regenerating shrubland and an adjacent mature, podocarp‐broadleaved forest, in the North Island, New Zealand, were compared over one season. Three traps were monitored in each site.2. Diversity indices did not group samples by site whereas the divisive polythetic classification analysis TWINSPAN showed that the two sites possessed clearly different communities. In the classification, site was of primary importance, with time of year, and trap position within site of secondary and tertiary importance respectively.3. Samples were compared at different taxonomic levels and using different subsets of the database. Determination of the main families, morphotyped to species or species complex, was found to be sufficient to classify most samples to the appropriate community group.4. The divisive classification procedure applied to four consecutive weekly Coleoptera samples over early summer, is suggested as a means of describing and identifying terrestrial arthropod communities characteristic of site and year of collection. This approach provides a potentially sensitive tool for monitoring terrestrial ecosystem

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1990.tb00795.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.1. To examine ecological and evolutionary aspects of caterpillar foraging behaviour, this study focused on observation of the individual foraging behaviour of two lepidopteran species,Pieris rapaeL. andEuphydryas phaeton(Drury), on their respective host plants.2. Periodic observations over the course of a day showed that the larvae move considerable distances, forage on the upper surfaces of leaves, and often immediately leave areas from which they have fed, leaving a pattern of dispersed herbivory.3. Differences in foraging behaviour were not found between the two species, even though one species is aposematic and the other is cryptically coloured, but there were significant differences in the foraging patterns ofP.rapaeon the two host plants, broccoli and radish.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1990.tb00796.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.1. The relationship between responses of the insect parasitoidCotesia rubecula(Marshall) to kairomones produced by the feeding activities of its host,Pieris rapae(L.), and patterns of parasitism were investigated under field conditions.2. Parasitoid adults aggregated in patches with the highest densities of host larvae but there was no commensurate increase in the rate of attack in these patches.3. The rate of attack was not limited by the availability of eggs.4. The rate of parasitoid attack was highest where feeding damage by the host was highest, irrespective of current host density.5. The rate of parasitoid attack was further influenced by host age distribution. Late instar larvae were less susceptible to parasitism than were early instar larvae. The rate of attack on early instar larvae occupying the same plants as late instar larvae was reduced. This reduction in rate of attack was due to limitations on parasitoid search time imposed by the increased feeding damage associated with large host larvae and by the increased time the parasitoid required to recover from an attack on these large host larvae.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1990.tb00797.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.1. Experimental studies have shown that larvae of threePierisbutterflies,P.rapaeL.,P.meleteMènètriés andP.napiL., are attacked by a parasitoid wasp,Apanteles glomeratusL. AlthoughP.rapaelarvae are parasitized heavily in the field,P.meleteandP.napiare infrequently parasitized successfully because they possess mechanisms for encapsulating parasitoid larvae and for avoiding parasitism.2. This study examines spatial and temporal variation in rates of parasitism of the threePierisspecies byA.glomeratusin the field. We attempted to determine whetherP.rapaepossesses any means of avoiding parasitism by this wasp, and then to deduce why bothP.meleteandP.napihave more distinctive avoidance mechanisms thanP.rapae.3. Our results indicate that in temporary habitats, which are the main habitats ofP.rapae, P.rapaeis able to escapeA.glomeratusin time and space by colonizing new habitats before the parasitoid arrives. In permanent habitats, however, such escape is not possible.P.rapaelarvae lack physiological or behavioural avoidance mechanisms of reducing parasitism rates in permanent habitats.P.meleteandP.napi, in contrast, live only in permanent habitats, where the parasitic pressure is potentially high, and have evolved active avoidance mechanis

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1990.tb00798.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.1. Previous studies which attempt to relate oviposition by female monarchs,Danaus plexippus(L.), to the cardiac glycosides of their milkweed host plants are reviewed and found to be defective.2. Here we followed ovipositing females in the field and recorded their oviposition behaviour on individualAsclepias fruticosa(L.) plants. The cardenolide glycoside and per cent nitrogen of each of these plants and also of a control set of plants was recorded.3. Milkweeds accepted by females, on which egg laying took place, had significantly lower mean cardenolide levels compared with rejected plants and a control sets of plants.4. Most oviposition (c.70%) took place on plants with intermediate cardenolide (CG) levels (=200–300 μg/0.1 g DW).5. The mean CG level inA.fruticosawas 345 μg/0.1 g DW (SD = 138,n=122, range 119–719).6. There was no relationship between monarch oviposition behaviour and plant per cent nit

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1990.tb00799.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.1. The effects of prey density and temperature on the feeding and development rates of several late instars of the larvae of three common European damselflies (Lestes sponsa(Hansemann),Coenagrion puella(L.) andIschnura elegansvan der Linden) were investigated in a laboratory experiment.2. Functional responses were used to estimate maximum feeding rates. Maximum feeding rates were compared between species, instars and temperatures by expressing prey consumption in terms of prey biomass consumed per unit predator biomass.Lesteswas capable of feeding at almost twice the rate of eitherCoenagrionorIschnura.3. Higher feeding rates led to faster development rates and there was an interaction between species and temperature. With the exception of those with very low feeding rates, larvae maintained at higher temperatures, but similar feeding rates, developed faster. Under similar conditions of temperature and feeding rate,Lesteslarvae developed faster than larvae of eitherCoenagrionorIschnura.4. Faster development rates at similar rates of food intake were achieved at the cost of reduced size‐increases between instars.5. The differences in the responses of the three species are discussed in the light of their respective life histories, and with reference to a recent model of population regulation in damselflie

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1990.tb00800.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Abstract.1. Microhabitat use and background matching by adultHipparchia semele(L.) in a coastal sand dune site in south Wales were studied during the flight period of 1986.2. Microhabitat use by both sexes is related to temperature and activity. When settling substrates are cool, typically during the early morning, most individuals are located on the warmest basking substrate, lichen patches. After a period of warming, males perch to locate mates on exposed areas of sand where there is a large field of view and where they are visually apparent. Egg‐laying females tend to settle on lichen patches throughout the day.3. Overall, females are maximally visually cryptic when settled on lichen patches with unexposed forewings. Male crypsis on lichen is less effective, but greater on most other substrates, than that of females. It is argued that individuals match lichen patches because this substrate is used when they are most liable to detection and capture by vertebrate predators. Male crypsis is probably a compromise between maximizing protection on lichen patches and requirements for resemblance to other substrates.4. The underside hindwing phenotype does not match sand. Background matching to this substrate is probably not important because it tends to be used when individuals are active and can effectively use secondary defence mechanisms.5. It is suggested that the apical eyespot and orange patch on the forewing underside have a dual role in secondary defence, acting as a startling and deflective device, being exposed by disturbed individuals and by those engaged in activities which may disrupt the visual crypsis afforded by the hindwing undersid

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1990.tb00801.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY