摘要:

Abstract.1In the absence of aphids, adult females ofAdalia bipunctata(L.) showed a greater reluctance to eat eggs than males.2Eggs and young larvae were more vulnerable to cannibalism than older larvae and starved larvae were more vulnerable than well‐fed larvae.3Both egg and larval cannibalism is inversely related to the abundance of aphids.4Eggs are a better food, in terms of larval growth and survival, than aphids.5In the absence of aphids interspecific predation occurred, but not equally, between the coccinellidsA.bipunctata, A.decempunctata(L.),Coccinella septempunctataL. andC.undecempunctataL.6Larvae and adults ofA. bipunctataandC.septempunctatawere reluctant to eat conspecific eggs painted with a water extract of the other species' eggs and larvae ofC. septempunctatawere more likely to die after eating a few eggs ofA.bipunctatathan vice versa.7These results indicate that cannibalism occurs mainly when aphid prey is scarce and is adaptive in that it improves the chances of survival, and coccinellids, to varying degrees, are defended against interspecific predatio

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1992.tb01062.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract.1Arthropod densities and apparent leaf damage were compared within the canopy ecotone and the shrub layer of a lowland rain forest in Cameroon, using a branch clipping method.2Most of the individuals collected consisted of ants (average 44%) and various herbivores (31%). Overall arthropod densities amounted to 17 individuals per sample, which, on average, consisted of 0.85 m2of foliage area. Arthropod densities were lower than on temperate foliage.3Arthropod densities were about 3 times higher in the canopy than within the shrub layer. In particular, ants and herbivores were significantly more abundant in the canopy than within the shrub layer. Usually, layer effects rather than site effects appeared to cause greater variance in arthropod abundance.4Arthropod species‐richness, as estimated by the number of operational taxonomic units sorted, was higher in canopy samples than in samples obtained from the shrub layer. However, apparent leaf damage was higher within the shrub layer (10.9%) than on the canopy (5.2%).5Possible factors responsible for the high densities of ants and herbivores on the canopy and for the high leaf damage within the shrub layer are discusse

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1992.tb01063.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract.1Swarms ofCulicoides impunctatusmales were examined in the field in Scotland. Most swarms were close to midge emergence/breeding grounds over a variety of vegetation, some of which clearly acted as swarm markers. Low light (0–1000 lux) and still/humid conditions favoured swarming.2Swarm size ranged between less than 10 and more than one thousand midges. The modal size was 200 individuals. The smallest swarms were usually columnar in shape and the larger swarms ovoid.3Midges behaved individually within swarms, moving in an elliptical manner characteristic of other dipterans in swarms.4Swarms were classified as either ‘persistent’ or ‘transient’ in terms of their shape, size and stability. Wind was the most influential factor in disrupting swarms.5Swarms were confirmed as mating sites forC.im

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1992.tb01064.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract.1The relationship between the fluctuation in total quantity of sugar available in the nectar ofCarduus acanthoidesinflorescences and the foraging behaviour of honeybeesApis mellifera ligusticawas studied in a patch under natural conditions.2Every day, three inflorescence populations coexisted, one for each day of the inflorescence life‐span. The maximum availability of sugar occurred in second‐day capitula from 12.00 to 15.00 hours.3Bee arrivals at the patch were positively correlated with the total availability of sugar as determined by sampling.4Bees responded to variation in the availability of sugar by visiting the inflorescence stage that was most rewarding at that time of day. Early in the morning, when the frequency of visits was low, the bees worked the third‐day capitula, which were the best available choice at that time. Similarly, beginning at 12.00 hours, bees switched to second‐day capitula. At the end of the day, some bees switched to third‐day capitula where a slightly superior quantity of sugar could be obtained from a small number of florets although other bees continued to work the second‐day capitula.5Individual bees switched to another inflorescence stage after a high proportion of their visits to a small number of capitula of one kind had provided a low reward.6The number of florets visited per minute per bee varied throughout the day and was positively correlated with the availabili

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1992.tb01065.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract.1Population dynamics ofCheilosia fasciatawere described based on a sampling programme covering all developmental stages.2Failure to oviposit and mortality which was due to parasitization of pupae contributed most to total generation mortality.3Abundance of older larvae was regulated by density‐dependent intraspecific competition for food.4These findings were reinforced by a field experiment which manipulated food levels and suggested that losses in numbers on ‘low food’ plots were in part compensated for by producing low‐sized

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1992.tb01066.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract.1Monarch butterflies,Danaus plexippus, from two overwintering populations, were found to haveOphryocystis elektroscirrhaspores on their scales at rates between 53% and 68%. The frequency of butterflies withO.elektroscirrhaspores remained about the same between sites and throughout the winter.2The spores, recovered from all parts of the body of the butterfly, were most numerous on the abdomen, particularly near the posterior third.3Butterflies with spores survived as long as those without detectable spores at 10.1°C ±0.4 SE and 78.3% r.h. ±0.6SE. Insects with spores held at 19.4°C ±0.4SE and 44.9% r.h. ±1.5SE showed a significantly higher rate of moisture loss and survived a shorter period than monarch butterflies without detectable s

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1992.tb01067.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract.1In natural populations, colonies of bumble bees vary in many important life history traits, such as colony size and age at maturity, or the number and sex of reproductives produced. We investigated how the presence of parasites in field populations of the bumble beeBombus lucorumL. relates to variation in life history traits and reproductive performance. A total of thirty‐six colonies was placed in accessible nest sites in the field and monitored at regular intervals throughout a season.2Among the life history correlates, early nest foundation was strongly associated with large maximum colony size, old age and large size at maturity, and this in turn with successful production of males and queens, as well as with the number of sexuals produced. Overall, reproductive success was highly skewed with only five colonies producing all the queens. Sixteen colonies failed to reproduce altogether.3The social parasitePsithyruswas abundant early in theBombuscolony cycle and preferentially invaded host nests with many first brood workers and thus disproportionately large size, i.e. those colonies that would otherwise be more likely to reproduce or produce (daughter) queens rather than males. To prevent nest loss,Psithyrushad to be removed soon after invasion. Therefore, the effects reported here can only be crude estimates.4Parasitoid conopid flies are likely to cause heavy worker mortality when sexuals are reared by the colonies. Their inferred effect was a reduction in biomass that could be invested in sexuals as well as a shift in the sex ratio at the population level resulting from failure to produce queens. We suggest to group the inferred correlates into ‘early events’ surrounding colony initiation and social parasitism, and ‘late events’ surrounding attained colony size in summer and parasitism by conopid flies. Our evidence thus provides a heuristic approach to understand the factors that affect reproductive success ofBombu

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1992.tb01068.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1992.tb01069.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1992.tb01070.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1992.tb01071.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY