摘要:

Abstract.1A naturally evolved arthropod community in a 6‐year‐old apple orchard was treated with three applications of permethrin; a second naturally evolved community was studied as an untreated control. Disturbance to the community was measured with Shannon's index of species diversity for the phytophagous and beneficial portions of the community.2Initially, there was a reduction in diversity of both phytophagous and beneficial arthropods because of the insecticide. Reduction in diversity was a result of both lower number of species and lower evenness of species abundance.3Two months after the last permethrin spray, there was no difference between diversity in the phytophagous community, but the beneficial community was more diverse in the treated orchard than in the untreated control.4The year after treatment there were few differences between the phytophagous communities, but the beneficial community was more diverse in the treated orchard than in the untreated orchard in May and early June; however, by September the beneficial community was less diverse in the treated orchard.5Although diversity statistics of the phytophagous communities were similar 15 months after treatment, differences still remained with the treated community being dominated by more r‐selected species and the control orchard dominated by more K‐selected species.6The arthropod community on apple has a high level of stability as reflected by its resilience to a severe external disturbance. This stability would allow for large, but infrequent, disturbances for pest management and still maintain long‐term ecological equilibrium in the

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01087.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1InDrosophila melanogaster, the cold‐shock tolerance of adult flies at ‐7°C increased 22% after a prior 2h exposure to 4°C as measured by LD50, the dose (degree minutes of exposure to subzero temperature) which resulted in 50% mortality.2Cold‐shock tolerance was further significantly increased by selecting cold resistant lines by exposure of adults (1) to 4°C for 2 h (short‐term chilling), or (2) to ‐7°C for 80–120 min (cold shock), or (3) to short‐term chilling followed by cold‐shock.3After ten generations of selection, the greatest increase in cold‐shock tolerance was found in flies selected using the combined exposure of short‐term chilling and cold shock. LD50s increased 33% in comparison with the unselected control strain when no chilling pre‐treatment was given prior to cold shock at ‐7°C.4The rapid cold‐hardening response increased 82% in the line selected by the short‐term chilling and cold‐shock regime.5The enhanced cold‐shock tolerance was relatively stable since no decrease was observed after four generations without selection.6This report shows the role of short‐term adaptation as well as selection in the capacity to survive low temperatur

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01088.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1Honey bees foraging for nectar on lavender (Lavandula stoechas) chose inflorescences with more of their flowers open. The number of open flowers predicted whether an inflorescence was visited by bees, inspected but rejected, or ignored. Inflorescences chosen arbitrarily by observers had numbers of open flowers intermediate between those of visited and ignored inflorescences.2Differences in morphological characters between types of inflorescence correlated with nectar volume and sugar weight per flower so that visited inflorescences had a disproportionately greater volume of nectar and weight of sugar per flower and greater variance in nectar volume.3Although there were significant associations between nectar content and the morphological characters of inflorescences, discriminant function analysis revealed discrimination on the basis of morphology rather than nectar content.4Visited inflorescences tended to have smaller than average flowers but bees tended to probe the largest flowers on visited inflorescences.5Choice of flowers within inflorescences is explicable in terms of the relationship between flower size and nectar content.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01089.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1The influence of fluctuating asymmetry on lifetime mating success of males of the damselflyCoenagrion puella(Odonata: Coenagrionidae) was investigated. Fluctuating asymmetry was measured as the difference in length of left and right fore and hind wings.2Males with more symmetrical wings enjoyed higher lifetime mating success.3Larger males, in contrast to a previous study of this species, also had higher mating success. This may be attributed to differences in the weather conditions prevailing at the time of the studies.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01090.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1The effects of superparasitism on the rate of development, adult size and mortality ofVenturia canescens(Hymenoptera: Ichneumonidae) were investigated. Parasitoids were reared from third (L3) and fifth (L5) instars of one of its hosts,Plodia interpunctella(Lepidoptera: Pyralidae) containing one, two or four parasitoid eggs.2Superparasitism increased the development time ofVenturiareared from both instars, but the developmental delay was more evident in wasps from L5 hosts.3The size of parasitoids from L3 hosts was unaffected by egg number, but wasps from both superparasitized L5 treatments were significantly smaller than those from singly parasitized hosts.4Parasitoid mortality was significantly higher in L5 than L3, but within instars did not differ significantly with egg number.5The results confirm that superparasitism may affect the fitness of both the adult female wasp and her progeny, and should therefore be incorporated into models of superparasitism as an adaptive foraging strategy.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01091.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1An examination of phenotypic variation in colour pattern was carried out on fourEristalishoverfly species using museum material.2The amount of phenotypic variation varied substantially among the species withE.arbustorumbeing the most variable. The other species showed a wide colour pattern range but less variation within that range (E.abusivusandE.nemorum), or a narrow range of colour variation (E.horticola).3Sexual colour dimorphism was apparent in all four species, but most pronounced inE.abusivusandE.nemorum.4There were good phenotype‐season relationships shown by both sexes in all species, except for femaleE.abusivusandE.nemorum, with paler insects being more abundant during the warmer summer months.5Female, but not male,E.arbustorumcollected at inland sites were on average paler than those collected at coastal sites. This observation is considered with respect to temperature during the developmental stages.6The function of colour plasticity in hoverflies is discussed with reference to the need to maintain optimal thermal conditions for activit

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01092.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1ELISA (enzyme‐linked immunosorbant assay) was used to identify the arthropod predators of two common herbivores of a desert lupine: the aposematic plant bugLopidea nigrideaand the ant‐mimetic plant bugCoquillettia insignis.2Despite the fact that the prey are closely related, the two antisera were sufficiently specific to distinguish between the antigen against which they were formed and the antigen of the other species: both antisera were 3 times as reactive against their homologous antigen as they were against their heterologous antigen.3In tests on gut contents of field‐collected predators, ELISA results were generally consistent with laboratory no‐choice data for the five most common arthropod species on lupine: there was a strong correlation between attack rates for each predator‐prey pair as measured in the laboratory, and per cent positive reactions in ELISA as measured using field‐collected predators. In particular,L.nigrideaantiserum was shown to be significantly less reactive against the crab spiderXysticus montanensiswhen compared toC.insignisantiserum, paralleling results of laboratory no‐choice experiments.4The usefulness of serological analysis as a tool for arthropod trophic link identification

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01093.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1Mortality and size variation (siphon length) inAedes cantanslarvae were examined in natural populations in northern England in 1989 and 1990.2Under crowded conditions, density‐dependent competition led to reduction in the size of both larvae and adults and increased larval mortality.3Larvae were also maintained in cages in the field at different densities. Results paralleled those for the natural populations in the ponds; larvae maintained at high densities showed increased mortality and reduced size.4Possible density‐dependent factors leading to mortality and size reduction include cannibalism and contact inhibition leading to food shortages.5The main density‐independent factor contributing to larval mortality was habitat desicc

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01094.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1Carpenter bees (Xylocopa californica arizonensis) in west Texas, U.S.A., gather pollen and ‘rob’ nectar from flowers of ocotillo (Fouquieria splendens). When common, carpenter bees are an effective pollen vector for ocotillo. We examined ocotillo's importance as a food source for carpenter bees.2The visitation rate of carpenter bees to ocotillo flowers in 1988 averaged 0.51 visits/flower/h and was 4 times greater than that of queen bumble bees (Bombus pennsylvanicus sonorus), the next most common visitor. Nectar was harvested thoroughly and pollen was removed from the majority of flowers. Hummingbird visits were rare.3Pollen grains from larval food provisions were identified from sixteen carpenter bee nests. On average, 53% of pollen grains sampled were ocotillo, 39% were mesquite (Prosopis glandulosa), and 8% were Zygophyllaceae (Larrea tridentataorGuaiacum angustifolium). Carpenter bee brood size averaged 5.8 per nest.4We measured the number of flowers, and production of pollen and nectar per flower by mature ocotillo plants, as well as the quantity of pollen and sugar in larval provisions. An average plant produced enough pollen and nectar sugar to support the growth of eight to thirteen bee larvae. Ocotillo thus has the potential to contribute significantly to population growth of one of its key pollinators.5Although this carpenter bee species, like others, is a nectar parasite of many plant species, it appears to be engaged in a strong mutualism with a plant that serves as both a pollen and as a nectar source during carpenter bee breeding peri

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01095.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1Competition in cattle dung pads between two dung beetles,Onthophagus feroxHarold andOnthophagus binodisThunberg, and the bush fly,Musca vetustissimaWalker, was investigated in laboratory experiments, to determine why spring fly abundance in the field did not fall following the introduction ofO. binodis.2At low beetle densities, the number of eggs laid by each species was reduced by the second species. A similar amount of dung was buried by each species alone or by both together.3At high beetle densitiesO. binodisegg production was substantially affected by each additionalO.ferox, butO.feroxegg production was not affected by each additionalO.binodis.Asymmetric competition occurred becauseO.feroxburied more dung thanO.binodis, and a greater proportion in day 1 (pre‐emptive dung burial).4O.feroxcaused greaterM. vetustissimaegg‐puparia mortality thanO. binodis.Mortality mostly occurred in youngM. vetustissimalarvae less than 1 day old. Total egg‐puparia fly mortality was correlated better with the dung buried on day 1 than dung buried on day 8 (pre‐emptive dung burial).O.binodisdid not add to fly mortality byO.feroxat high densities because of asymmetric competition between the

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01096.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY