摘要:

Abstract.1The seasonality of arboreal arthropods foraging within the crown of the canopy treeArgyrodendron actinophyllum. Edlin (Sterculiaceae) was studied in a subtropical rain forest near Brisbane, Australia, during 2 years with interception traps and restricted canopy fogging.2Minimal air temperatures explained most of the seasonal variance in arthropod‘density activity'. However, the host phenology was important for several phytophagous groups. Rainfall, relative humidity and lunar phase influenced arthropod activity slightly.3Seasonal ranges were significantly different among arboreal guilds and were related to food resource availability in time, associated with both the host and the rainforest environment. Seasonal peaks of herbivores were more marked than in tropical rain forests, but less sharp than in temperate woodlands.'4Quantitative changes in arthropod density activity and abundance were important for most groups, with a marked trough during cool and dry months. The numerical contribution of most arthropod guilds to the arboreal community was not constant throughout the year.5Seasonal changes in the species composition of the arboreal community appeared not as a succession of well‐defined subcommunities throughout the year, but as a continuum of species of extended seasonal ranges.6This subtropical insect‐plant system presented several phenological features which were classified under tropical and temperate characteristics. This partition is open to discu

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00217.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1InTribolium castaneumHerbst, in which dispersal is genetically determined, it is possible to select for strains that are characterized by high and low dispersal, High dispersal (HD) beetles are better adapted than low dispersal (LD) beetles for colonization, as can be seen from differences that exist between the two groups with regard to several life‐history parameters.2Comparisons were made between the dynamics of seventy‐two HD and seventy‐two LD populations. Generation length in HD populations was significantly shorter than in LD populations. After 91/2weeks, in open treatments (from which dispersal away from the set was allowed), HD populations had more beetles than LD populations, whereas in closed treatments (from which dispersal away from the set was not allowed) the opposite was true.3These findings may explain the maintenance of the genetic variability of dispersal behaviour in natural populations ofT.cast

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00218.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1The defence capability of pine sawfly larvae reared on Scots pines with low or high concentrations of resin acids was determined in a field experiment, where larvae were exposed to predatory ants, and in a laboratory experiment in which the rate of defence droplet replenishment was measured.2Larvae on low resin‐acid shoots disappeared faster than larvae on high resin‐acid shoots when exposed to predatory ants.3Larvae fed high resin‐acid needles produced 50% larger defence droplets than larvae fed low resin‐acid needles.4In an additional experiment high predation pressure was simulated by repeatedly removing defence droplets. Larvae responded by feeding more on tissue rich in resin acids, but at the cost of a reduction in growth rate.5Based on these data and earlier findings that survival and development of sawfly larvae are negatively affected by high resin‐acid concentrations, we conclude that pine sawflies face a dilemma of conflicting demands, i.e. although high needle resin‐acid concentrations enhance defence capability, they also reduce growth and survival. Our data also suggest that it is not necessarily the ovipositing female that has to balance this trade‐off: plasticity in larval feeding behaviour provides larvae with a means to at least partly solv

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00219.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1Seasonal polyphenism is studied in a community of five African butterflies of the genusBicyclusat the transition between a wet and a dry season from May to July.2Butterflies characterized by large eyespots and, especially inB.sufitza(Hewitson), a pale band (the wet season form) are replaced over this period by butterflies lacking conspicuous wing markings (the dry season form, dsf). The latter butterflies also tend to be larger, but more variable in size. Butterflies of an intermediate phenotype are recruited over a comparatively short interim period.3This turnover coincides with a period of declining temperature and drying of the habitat, including the grasses on which larvae feed. Butterflies are progressively more likely to rest on brown leaf litter rather than on green herbage.4A relationship with temperature is supported by laboratory experiments withB.saJitzaandB.anynana(Butler) showing that increasingly extreme dsf butterflies develop with decreasing rearing temperature in the final larval instar.5Some differences in behaviour and activity were observed between the seasonal forms. Butterflies of the dsf develop ovarian dormancy and fat bodies. They can survive to reproduce at the beginning of the rains in November.6Capture‐recapture experiments showed that the adult butterflies have a comparatively long life expectancy and are quite sedentary.7The results are discussed in relation to a hypothesis linking the polyphenism to seasonal changes in resting background and selection for crypsi

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00220.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1Adaptation to life in caves, as a seasonally constant environment, is expected to affect several life history traits. In this paper we investigate the age structure and phenology of twenty‐sevenDolichopoducave cricket populations from artificial and natural caves subjected to different environmental regimes and to different availability of food resources.2Morphometric data clearly revealed the occurrence of different age structures and phenology, basically indicating two contrasting patterns.3In artificial caves, which have been colonized byDolichopodaonly in historical times and where food resources and climate are chiefly dependent upon surface environment, age structure was seasonal. In contrast, in most natural caves, where cricket colonization appears to be much older and stability of both climatic parameters and trophic resources is higher, age structure was diverse and aseasonal.4However, a seasonal age structure also occurs in natural caves characterized by either recent origin or by a low temperature regime. This suggests that age structure inDolichopodais influenced by historical factors, stability of food resources and also by environmental stres

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00221.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1The abundance, survival, and causes of mortality ofCameraria hamadryadella(Clemens) (Lepidoptera: Gracillariidae) were examined on four host plant species in Virginia, U.S.A.Quercus albaL. andQ.rubraL. are native within the geographic range ofC.hamadryadella, andQ.roburL. andQ.benderiBaenitz are exotic.Q.roburis native to Europe, North Africa, and Asia and was probably introduced prior to 1850, andQ.benderiis of hybrid origin and introduced to cultivation before 1900.Q.albaandQ.roburare in the subgenusLepidobalanus(white oaks), andQ.rubraandQ.benderiare in the subgenusErythrobalanus(red oaks).2Larval mines ofC. hamadryadellawere abundant on both white oak species, including the exoticQ.robur, but were rare on host plants in the red oak subgenus. Un‐hatched eggs ofC.hamadryadellawere not observed on red oaks. Other observations on host distribution indicate thatC.hamadryadellais rarely found on red oaks. These observations are interpreted as circumstantial evidence thatC. hamadryadellagenerally avoids ovipositing on red oaks.3Survival ofC.hamadryadellato the adult stage was similar among all host species, but larvae tended to survive longer on hosts in the red oak subgenus. The observation of higher survival rates of early instar larvae on red oaks suggests that no nutritional or secondary chemical barrier reinforces the observed pattern of oviposition.4Significant differences in the distribution of the causes of mortality were detected between native and exotic host plant species. Larvae and pupae on native hosts were more likely to die because of predation, while those on exotic host plants were more likely to die because of parasitism and host feeding by adult female parasitoids. This pattern could arise because parasitoids prefer to forage on exotic host plants or because predators avoid foraging on exotic plants.5This study shows forC. hamadryadellathat the only barriers to colonization and use of exotic hosts, in the white and red oak subgenera, are the presence of cues sufficient to stimulate oviposition and/or the absence of cues to deter oviposition. It also suggests that the presence of closely related native host plants in the region of introduction will increase the probability that exotic plants will be colonized by phytophagous insect

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00222.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1Highly productive and st,ructurally diverse angiosperm communities occur on sub‐Antarctic Marion Island, yet cryptogams are the main source of energy and nutrients for five of the six native weevil species (Curculionidae: Ectemnorhinini) that occur there.2Previously it has been hypothesized that low‐temperature regimes, during the Pleistocene, precluded angiosperm herbivory. This hypothesis was based,inter alia, on the assumption that at low temperatures feeding on bryophytes is more nutritionally advantageous than feeding on vascular plants.3This assumption was tested by comparing the consumption rate (CR) and approximate digestibility (AD) (mass and energy) of bryophytes and angiosperms in twoDusmoecetesspecies indigenous to Marion Island.4The approximate digestibility ofBlepharidophyllum densifolium(Scapaniaceae) energy and dry mass were similar forD.marioniJeannel adults at 5°C and at 10°C.D.similis(C. O. Waterhouse) adults fedAzorella selagoHook (Apiaceae) leaves also had similar AD for food dry mass and energy at 5°C and at 10°C. However, the performance ofD.similisonA.selagoleaves and flowers at 5°C was better than that ofD.marionion bryophytes at both temperatures.5Bryophyte feeding does not appear to be nutritionally more advantageous at low temperatures in the sub‐Antarctic, nor does angiosperm herbivory appear to be comparatively disadvantageous at low temperatures, althoughD.similisdoes not feed onAcaena magellanica(Lam.) (Rosaceae) at 5°C. It seems likely that moss‐feeding evolved in response to an absence of angiosperms during glacial periods, rather than because of a nutritional advantage associated with bryophagy at low

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00223.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1Males operate within a finite energy budget and cannot produce limitless supplies of sperm. On the other hand, when a female mates with a second male while still containing fertile sperm from a rival male, selection should favour the male that inseminates more sperm. Optimal strategy should thus be for males to exercise discretion in the allocation of sperm to individual females. Assuming the outcome of sperm competition to be based on either the raffle or kamikaze principles, the sperm competition hypothesis predicts a positive association between the probability that the sperm will find themselves in competition with sperm from rival males and the number of sperm inseminated.2The beetle,Tenebrio molitorL., behaves in accordance with this hypothesis. Males accompanied by a rival male before and during mating inseminate more sperm per ejaculate than unaccompanied males. Accompanied males are also faster to initiate mating and more likely to show post‐copulatory guarding. Adjustment of number of sperm inseminated was shown by males subjected to both long‐term (5 days) and short‐term (5 min) exposure to potential intrasexual competitors. Individual males exposed to both levels also demonstrated the ability to adjust their ejaculate according to socio‐sexual situation.3We conclude that maleT.molitoradjust the number of sperm they inseminate according to some perception of the risk of sperm comp

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00224.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1200 of 1137 species of British microlepidoptera make a single marked change in feeding habit as they grow.2Most numerous are species that change from leaf mining to one of case bearing, spinning, tying and rolling or concealed feeding, and species that change from concealed feeding to case bearing or spinning, tying and rolling.3Although in some instances numbers of closely related species make similar changes in behaviour, most changes observed are scattered among subfamilies.4Leaf miners have considerably smaller adults than concealed feeders, which themselves are smaller than external feeders and spinners, tiers and rollers. When case bearers are excluded from the analyses, species that remain as leaf miners or concealed feeders throughout larval development are on average smaller as adults than those that start out with these feeding habits but later change.5We suggest a number of reasons why larvae might make such fundamental switches.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00225.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1Egg‐size variation over the reproductive span of laboratory‐reared females is described in two species of cotton stainers:Dysdercus fasciatusSign. from woody Malvales andD.cardinalisGerst. from herbaceous Malvales.2Egg size increases with maternal age due to a decrease in clutch size as maternal age advances in both species.3The two species are similar in size, but egg size is about 28% larger and clutch size about 19% smaller inD.fasciatusthan inD.cardinalis. These contrasts may be related to the host‐plant biology which differs between the two sp

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00226.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY