摘要:

Abstract.1. The humidity responses of Asaphidion pallipes (Duftschmid) and Bembidion spp. were studied at various temperatures in choice chambers.2. Several species initially showed a hygropositive or indifferent response. Other species had a hygronegative reaction which later changed to a hygropositive one. The duration of the hygronegative reaction varied with species, age, temperature and relative humidity. B.litorale (Olivier) and B.semipunctatum (Donovan) change response when they have lost 8–9% of their initial body weight as water.3. The survival time of species of Bembidion under dry conditions was short compared with that reported for many other carabid beetles. Newly emerged adults of B.argenteolum Ahrens that had been kept away from sand for 3 weeks had lower transpiration rates than any other species. Young adult Bembidion had lower transpiration rates than those in the breeding phase, larvae and dead adults. Transpiration rate appeared to be inversely proportional to the relative humidity whereas there was a non‐linear increase in weight loss with increasing temperature.4. The species gain most water by drinking and/or from food.5. There was no correlation between humidity response and transpiration rate or ability to tolerate dry conditions of the species. There was, however, a correlation between behaviour/habitat affinity and humidity response. Diurnal species, living in sandy or silty, half shady‐exposed habitats had an initial hygronegative response, whereas those which hide among gravel/stones, leaves or vegetation were indifferent or hygropos

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1985.tb00734.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.1. Mallophaga and Acari were collected from 324 reed buntings (Emberiza schoeniclus (Linnaeus)) captured in a communal winter roost between October 1980 and March 1981.2. Frequency distributions of one of the mallophagan species, (Philopterus docophorulus (Zlotorzycka)), of the aggregated Mallophaga, and of the aggregated Acari, conform well with a negative binomial model. The remaining three mallophagan species collected were not present in sufficient numbers to describe a frequency distribution.3. The ratio of nymphs to adults in the mallophagan community increased significantly in the second half of the roosting period (January–March) indicating the onset of increased reproductive activit

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1985.tb00735.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.1. Time‐budgets are constructed from censuses of hoverflies. Larger species spend less time in flight.2. Most species are active under similar conditions of light intensity, but a shade‐tolerant (Melanostoma scalare Fabr.) and a sun‐loving species (Metasyrphus corollae Fabr.) were identified.3. Large species become active (i.e. move, by flying or feeding) at lower temperatures than small ones, except M.scalare, which is tolerant to cool temperatures. This means that, M.scalare apart, the order of species appearing during the day is size‐dependent, largest first.4. Previous claims about the diel periodicity of syrphids can be reconciled by considering the importance of individual thermal balance.5. Tolerance to low temperatures in small hoverflies is associated with feeding on anemophilous pollen; this may indicate a proline‐fuell

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1985.tb00736.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.1. Two species of parasitoids (Anisopteromalus calandrae (Howard) and Heterospilus prosopidis Vier) attacking the bruchid beetle, Callosobruchus chinensis (L.), show marked inverse density dependent relationships between per cent parasitism and host density per patch.2. These patterns are well described quantitatively using data on the spatial distribution of searching time by the parasitoids and their attack rates on patches of different host density.3. A model of optimal foraging predicts just the opposite (i.e. density dependent) patterns of parasitism.4. Both density dependent and inversely density dependent spatial patterns of parasitism can be explained mechanistically in terms of (a) the allocation of searching time in patches of different host density and (b) the maximum attack rate per parasitoid that constrains the extent of host exploitation within a patch.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1985.tb00737.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.1. Three species of Tanypodinae (Chironomidae) were found in an acid and iron‐rich stream in southern England. Maximum abundance was achieved in summer and they were sparse at other times. Individuals were aggregated on the stream bed and were overrepresented in accumulations of leaf litter.2. The diets of all three species consisted of a mixture of prey (prominently detritivorous chironomid larvae) and detritus. More detritus and fewer prey were taken in winter than in summer.3. When comparing large tanypod species with small and, intraspecifically, late instars with early, the proportion of guts containing prey increased with increasing body size.4. Stonefly larvae were more prominent in the diet of Zavrelimyia barbatipes (Kieffer) in summer than in winter but for the other two species the reverse was true. A bigger proportion of Trissopelopia longimana (Staeger) guts contained prey in early summer than in August whereas more Macropelopia goetghebueri (Kieffer) guts contained prey in August. This was apparently a consequence of seasonal differences in the distribution of body size among the populations of these two species.5. The stream contains two further common predators, Plectrocnemia conspersa (Curtis) and Sialis fuliginosa Pict. These are important predators of tanypod larvae but might also compete with them since they severely deplete populations of prey taken in common.6. Analysis of the food‐web in Broadstone Stream reveals remarkably high values of connectance (C and Cmax) and of species richness times connectance (SCmax). Such characteristics are theoretically associated with fragile and dynamically unstable food webs, and may be found in ‘constant’ environments. There is also an apparently unusual prevalence of omnivory in the co

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1985.tb00738.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.1. Field observations on the distribution of Philaenus spumarius (L.) on pearly everlasting (Anaphalis margaritacea) and alfalfa (Medicago sativa) showed that the range of feeding sites exploited increased with instar. Development of trichomes, depth of xylem elements, and tissue hardness were measured as possible factors determining the suitability of sites on food plants.2. Spittlebugs caged outside their normal feeding sites experienced difficulty feeding. Experimental removal of trichomes showed that trichomes prevented younger instars from feeding on the stem. The depth of the xylem elements and tissue hardness were not significant barriers to feeding near the stem apex.3. By caging fourth and fifth instar nymphs at increasing distances below the terminal bud on A.margaritacea stems, we showed feeding ability declined with distance below the apex, and feeding was more restricted in fourth compared to fifth instars. A similar decline was demonstrated in experiments with fifth instars on M.sativa.4. On A.margaritacea, this restriction was associated with increasing tissue hardness of the stem with distance from the apex and the presence of trichomes in regions with hard tissues. On M.sativa the associated barriers were a combination of tissue hardness and reduction in the availability of xylem vessels in the penetrable region of the stem. Although the tissues impeding stylet penetration differed in the two hosts, the critical factor in both species was the increase in the amount of lignification of those tissues at increasing distances from the terminal bud.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1985.tb00739.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.1. Two aphid species feed exclusively on pine needles, Schizolachnus pineti (Fabr.) occupying only the outer (curved) surface with Eulachnus agilis (Kalt.) showing a preference for the inner (flat) surface.2. Despite E.agilis favouring and S.pineti avoiding senescing needles, both species show a significant tendency to share shoots and needles in the field.3. The same association is also apparent under laboratory conditions, although E.agilis is randomly distributed between needles in the absence of S.pineti.4. E.agilis was found to benefit through increased survival and faster growth rates, by feeding on the same shoots and needles as S.pineti.5. It is suggested that E.agilis may be able to detect and exploit an improvement in the nutritive quality of needles brought about by the feeding activity of S.pineti colonies.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1985.tb00740.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.1. Aggregation and mating of Thrips major Uzel and Thrips fuscipennis Haliday (Thysanoptera: Thripidae) in the 1‐day flowers of Calystegia sepium (L.) R.Br. are described.2. The number of thrips per flower increased rapidly after flower‐opening at dawn and decreased during the evening and following morning.3. Males patrolled the corolla, attempting to copulate with any females that landed. Their movement was affected by the density of thrips on the corolla. Most females were among the stamens and style, apparently feeding on pollen.4. These thrips were also abundant in flowers of Filipendula ulmaria (L.) Maxim. They fed on pollen, and grains adhered to them. They may be significant pollinators because of their high frequency of flights.5. The aggregations appear to be a simple consequence of general flower‐finding responses to colour and scent that are particularly elicited by flowers of C.sepium and F.ulmaria. The ecological significance of male aggregations is disc

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1985.tb00741.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.1. A laboratory experiment was conducted to determine the outcome of competition between two species of carrion‐breeding Diptera for food at two levels of resource patchiness.2. Adults of Fannia howardi Malloch (Muscidae) and Megaselia scalaris Loew (Phoridae) were released into a large population cage and were given access to three 2g sections of pork kidney in one treatment (low patchiness) and to twelve 0.5g sections in the other (high patchiness).3. Increasing the patchiness of the resource resulted in reduced overlap in the distribution of the two species, and therefore less interspecific competition. However, this did not result in improved survival of the poorer competitor, F.howardi. Both species aggregated their eggs at high patchiness, and therefore suffered from increased levels of intraspecific competition.4. The experiment shows that increasing patchiness in this way could lead to prolonged coexistence, as has been predicted in other studie

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1985.tb00742.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.1. Overwintering of the mosquitoes Anopheles atroparvus van Thiel and Culiseta annulata Schrank, both of which feed on blood throughout the year, is compared.2 The aquatic stages, males and gonoactive females of A.atroparvus disappear before winter, leaving a generation of inseminated, nulliparous, diapausing females to overwinter. Blood meals taken by diapausing females merely serve to maintain fat reserves. After re‐activation in March–April, gonoactive life expectancy appears to be rather short. Aquatic development at this season is slow and eggs laid in the spring do not significantly affect adult densities until June.3. Aquatic stages, males and gonoactive females of C.annulata are present throughout the year. This species appears to be able to overwinter without recourse to diapause, females passing the winter in alternating, or lasting, states of cold‐induced quiescence or normal gonoact

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1985.tb00743.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY