摘要:

Abstract.1. An experiment is presented that tests the hypothesis that the extrafloral nectaries ofChssia fasiculatareduce herbivory by attracting pugnacious ants that deter herbivores, and tests the equivalence of two methods of ant exclusion: treatment with Tanglefoot, and nectary excision.2. The protectionist hypothesis is not supported; treatment plants produced as many pods as did control plants.3. Treatment with Tanglefoot is equivalent to nectary excision in terms of pod production4. A graphical model is presented that relates the efficacy of ant protection to plant density and ant activity.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1984.tb00848.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Abstract.1. Discrete patches of aphids were artificially created in winter wheat fields in 1982 and in 1983 using field cages.2. Aggregation by polyphagous predators at these patches following cage removal was measured using pitfall traps in patch and control areas.3. Several species of polyphagous beetle (Carabidae and Staphylinidae) aggregated in these patches while other species did not.4. The consequences of aggregation by polyphagous predators to a single prey species are discussed.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1984.tb00849.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Abstract.1. This study was conducted in Greece using a wild strain of medflies (Ceratitis capitata[Weidemann]) to assess age‐specific vital rates in adults, and development and survival in pre‐adults when reared on different host fruit. The results were used to construct life tables.2. The demographic analyses suggested that there are basically four aspects of the medfly's life history which are of major importance: (i) multiple, highlyoverlapping generations; (ii) high net reproduction while young; (iii) high larval fitness in certain hosts; (iv) lack of diapause.3. Reasons why these characteristics are felt to be important are briefly discus

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1984.tb00850.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Abstract.1.Atriplex canescens(Pursh) Nuttall andA.polycarpa(Torrey) Watson (Chenopodiaceae) support twelve morphologically distinct gall types in southern California. Thirty‐seven common species of parasitoids, predators and inquilines are associated with these galls.2. The galls incited by eight members of theAsphondylia atriplicisCockerell (Diptera: Cecidomyiidae) species complex are linked into a single, interacting community through shared hymenopterous parasitoids and inquilines.3. Cluster analysis (UPGMA) grouped the fifteen most common species of Chalcidoidea into three host guilds of five species each: (1) specialists in tumour stem and blister leaf galls onA.canescens, (2) specialists in woolly stem galls onA.poiycarpa, and (3) generalists that attack all galls. Guild 1 dominated the galls with which it was primarily associated, while guild 3 dominated the remainder.4. The abundances of the parasitoids of the tumour stem and blister leaf galls were negatively correlated with the abundances of two organizer species, a gall‐forming inquiline,Tetrastichus cecidobroterGordh and Hawkins, and an internal, larval—pupal parasitoid,Tetrastichussp. B. The abundances of nine of the twelve most common chalcidoids were not correlated with the abundances of all coaccurring species in six other galls.5. Host seasonality partly determines parasitoid population dynamics and guild structure. Parasitoid dominance increased with gall duration, suggesting that parasitoid competition depends on resource stability. The two continuously available galls were dominated by their specialist guild, while all seasonal galls were dominated by generalists. The subdominant specialists of woolly stem galls may represent competitively inferior species that utilize those galls opportunistically, because of the gall's widespread distribution and 9–10 month yearly availability.6. Sites in the Colorado Desert and chaparral that supported several gall types showed stable relative abundances of the major parasitoid species, whereas sites in the Mojave Desert that supported only woolly stem galls had unpredictable parasitoid species assemblages.7. The competitive success ofAtriplexgall parasitoids may depend primarily on voltinism (multivoltine species dominated univoltine species) and mode of feeding (phytophagous, mixed entomophagous—phytophagous and facultatively hyperparasitic species in general dominated strict primary par

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1984.tb00851.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Abstract.1.Puliciphora borinquenensis(Wheeler), a very small phorid fly in which the female is apterous, breeds in small patches of decomposing organic matter such as dead insects.2. Females leave the shelter of oviposition sites during the afternoon and ‘parade’ in exposed places making vigorous abdominal pumping movements which probably help to disperse a pheromone.3. Males exhibit one of four reproductive routines. In the first they perform rapid sequences of stationary copulations with different parading females, achieving rates of 0.66 females min‐1for periods of 30min (Al). In the second (A2) they wait on oviposition sites and grab non‐parading females which have recently arrived.4. In the third routine a male airlifts a parading femalein copulato an oviposition site (Bl); in the final type of routine, females are airlifted and then deposited randomly when oviposition sites cannot be found (B2).5. Males are able to learn the location of oviposition sites and this enables them to transport large numbers of females (up to thirty‐three per male) to sites at a high rate (0.5 females min‐1).6. Immediately a female is released after a B routine, the male follows her closely for up to 10s. This is thought to represent a phase of non‐contact guarding, suggesting the occurrence of sperm competition.7. Individual males persist with either A or B routines for long periods (c. 30 min), but they are able to switch between routines.8. Young males (<27 h after emergence) carry out A routines 18 times more commonly than B routines, whereas older males carry out A routines only 1.6 times more commonly than B routines. The choice between A and B routines in older flies does not depend on male or female density.9. Males benefit from B routines because the eggs they fertilize are likely to reach oviposition sites, but they pay a considerable energy cost. A routines, on the other hand, are energetically cheaper, but mated females are less likely to reach oviposition sites unless they are subsequently transported by B males. An A male can then benefit provided his sperm are not completely displaced by th

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1984.tb00852.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Abstract.1. Records of parasitism from the field and host choice experiments suggest that most parasitoids of syrphids are monophagous. A few are oligophagous.2. To elicit egg release, females require a stimulus from the host haemolymph. Differential response to haemolymph cues by females may account for the observed pattern of host relations.3. Differences in host ranges and timing of female flight periods probably characterize most of the parasitoids studied.4. In one case of two monophagous parasitoids,Diplazon pectoratorius(Thunberg) andSyrphophilus tricinctorius(Thunberg) attacking the same hostSyrphus ribesii(L.) no partitioning was found.Stricinctoriusis, however, a superior intrinsic competitor.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1984.tb00853.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Abstract.1. Animals and plants may gain protection by reminding would‐be aggressors of failure, or an unpleasant experience following an attempt at capture and ingestion. Thus they need not bemistakenfor noxious or dangerous prey; defence is adequate if the aggressor is forced to recall the attributes of such species, or the disagreeable sequela to a previous assault upon them.2. Batesian mimics and mildly toxic Mullerian mimics can also add to their repertoire by such defensive strategies.3. Several examples of this phenomenon, designatedaide mémoiremimicry, are describ

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1984.tb00854.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Abstract.1. An investigation was conducted to determine the effects of variation among individual plants ofRudbeckia laciniataL. on the distribution and abundance of the aphidUroleucon rudbeckiae(Fitch).2. Wild plants were examined repeatedly for up to 21/2years to obtain information about plant growth and flowering, and about aphid densities on individual plants.3. Aphid densities on individual plants were positively associated with several measures of plant vigour, including height, growth since previous year, and occurrence of flowers.4. The colonization of plants by alate aphids was more highly correlated with plant height than with plant exposure. Aphid densities on individual plants were more strongly associated with plant height than with number of colonists.5. In all years there were many hosts which were never colonized by aphids. Some of these plants produced shoots but did not flower. Experimental infestation of these plants showed that they were unsuitable for aphid growth and reproduction. Some plants which did flower and which escaped aphid infestation were nevertheless suitable hosts. Previously unsuitable host individuals were able to support aphids when grown under glass‐house condition

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1984.tb00855.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Abstract.1. Migration pattern and mass appearance of the hoverflyMetasyrphus corollae(F.) (Diptera, Syrphidae) were investigated on the SE coast of Sweden in 1981. In total, 4433 hoverflies, belonging to fifteen species, were collected in water traps during 4–6 August. All but 2.2% wereM.corollae, 3282 specimens being caught on 4 August, 1021 on 5 August and thirty‐five on 6 August.2. The sex ratios (♂/♀) on these dates were 1/1.6, 1/1.3 and 1/1.7. The average dry weights did not significantly differ between sexes (males 4.01 mg, females 4.02 mg).3.M.corollaefemales were reproductively immature.4. Females mostly hadSeneciopollen in their guts while males mainly hadRubuspollen. The average number of pollen grains per specimen was 210 for females and 1100 for males.5. In the summer 1980 aphids were numerous, forming a basis for a high abundance of adult hoverflies (with hibernating larvae) in 1981. Aphid density in 1981 was low and stimuli inducing egglaying were sparse. It is suggested that this pattern of aphid abundance triggers migration inM.corollaeand in other aphidophagous species at irregular in

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1984.tb00856.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Abstract.1.Nephila clavipes(L.), a common spider in neotropical forests, discriminates some unpalatable prey and releases them unharmed from its web. Release is not accidental but results from a specific behavioural sequence.2. Field trials with twenty‐seven butterfly species showed that spiders respond consistently to butterfly species and higher taxa. Ithomiinae and some Danainae are almost always released while Heliconiinae, Nymphalinae, Acraeinae, Pieridae and Papilionidae are usually eaten.3. Paired tests showed that an immediately preceding experience with a different butterfly did not reveal any change in the spider's usual response to a particular butterfly.4. Warning coloration is not involved in spider response. Spiders rejected the models but ate the mimics of two different butterfly species pairs. Distastefulness is probably signalled by chemical cues.5. Some unpalatable butterflies stay motionless when entangled and while the spiders release them. Motionlessness in webs seems to be a requisite to allow recognition of their distastefulness without being bitten by the spider.6. Spiders differ from vertebrates in the prey accepted and in rejection mechanics. Although there is no indication of learning, spiders may select butterflies for distastefulness, chemical signals and motionlessness, at the individual leve

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1984.tb00857.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY