摘要:

Abstract.1Juveniles of the Australian lycaenid butterfly,Jalmenus evagorus(Donovan), secrete to ants a solution of sugars and amino acids, primarily serine. The attendant ants protect the larvae and pupae from parasites and predators.2The effect of caterpillar nutrition on the defence provided by ants was investigated. Potted food plants ofAcacia decurrenswere either given water containing nitrogenous fertilizer or were given water alone. Fertilized plants had a higher nitrogen content than unfertilized plants.3Fifth instar larvae ofJ.evagorasfeeding on fertilized plants attracted a larger ant guard than those feeding on unfertilized plants. In the absence of caterpillars, ants were not differentially attracted to fertilized and unfertilized plants.4In the presence of ants, over a 10‐day period, larvae on fertilized plants survived better than larvae on unfertilized plants. In the absence of ants larvae survived equally on fertilized and unfertilized plants. It is concluded that larvae on fertilized plants attracted a larger ant guard, and thereby survived better, than larvae on unfertilized plants.5Adult females ofJ. evagoraspreferred to lay egg batches on fertiized, rather than unfertilized plants, but they did not lay larger egg batche

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00186.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1The oviposition behaviour ofSimulium reptansL. is described from two sites on the River Spey, Scotland. Female aggregations were observed immediately downstream of oviposition sites and were composed mainly of gravid flies (range 60–80%0) together with smaller numbers that were either freshly bloodfed (range 2–17%) or infected with mermithid nematodes (range 0–30%).2The time from landing on the oviposition sites to the onset of oviposition was recorded. The time in the presence of greater than 1‐day‐old eggs did not significantly differ from sites with no eggs present. However, the presence of freshly laid or I‐day‐old eggs significantly shortened the time to onset of oviposition. The cues that elicit oviposition are unknown but it is speculated that they may involv

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00187.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1Four species of staphylinids were caged separately on wheat and their effect on the population development of the grain aphid,Sitobion avenae(F.), was investigated over two seasons.2A novel field cage design was used to exclude all but the staphylinid species under investigation.3Predator effects were compared with total‐exclusion cages in which all predators and parasitoids were kept out.4During a high‐density phase of aphid population development onlyPhilonthus cognutus(Stephens) significantly influenced aphid population numbers.5At low aphid densities,Tachyporus obtusus(L.),T.chrysomelinus(L.) andP.cognatusreduced aphid population levels.6The experiments showed thatTachyporusspp. can reduce the numbers of cereal aphids prior to the exponential phase of aphid population increase and thatP.cognatuscauses some reduction at both the stages of aphid population growth investiga

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00188.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1Female eggs ofCoccophagus atratusare deposited within the haemolymph of coccoid scale insects. Male eggs are deposited on to late larval and prepupal stages of parasitoids of scale insects, including conspecifics.2When presented with either one host type or a combination of both host types, femaleC.atratusdeposit all their available eggs, assigning the appropriate sex egg to each host encountered. Brood sizes are not adjusted for different combinations of hosts.3Behavioural observations show that females do not move away from patches of hosts until all their eggs are laid, regardless of the host type.4Brood sex ratios varied with changes in the relative availability of hosts for males and hosts for females. When both host‐types were present in equal numbers, male biased sex ratios resulted (mean ±SEM =0.71 ± 0.009) and when 70% of hosts provided were suitable for female eggs, mostly female‐biased sex ratios resulted (mean ± SEM = 0.37±0.01).5Our results do not fit predictions based on the assumption that a sex ratio of 0.5 should be expected inC.atratus. Observed sex ratios indicate that the unusual life histories of these parasitoids need to be taken into account in explanations of their sex

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00189.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1Second instarFilippia geminade Lotto scale insects are the preferred hosts of femaleCoccophugus atrutusCompere larvae. These scale insects were found on their host plants,Chrysanthemoides moniliferaNorlindh andCliffortia strobiliferaMettenius, only at certain times during a 1 year sampling programme.2Late larval instars and prepupae ofC.atratus, and aMetaphycusspecies, are the preferred hosts of maleC.atratuslarvae. These hosts, although they occurred on the same host plants as hosts for femaleC.atratus, were most numerous at different times during the sampling period.3The ratio of hosts suitable forC.atratusvaried from a predominance of hosts suitable for females through to a predominance of hosts suitable for males. Sex ratios of adultC.atratusfollowed a similar trend but did not reflect, exactly, the ratio of available hosts. Differences in mortality between sexes and hyperparasitism may account for this anomaly.4Variable population sex ratios observed inC.atratusapparently result from the behaviour of individual females in which brood sex ratios are dependent on the relative availability of hosts for males and hosts for females. This behaviour, in turn, may result from variability in the host population structure but may also result from selection pressures operating at the time that heteronomous hyperparasitism evolved.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00190.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1This study investigates sperm competition inCullosobruchus maculatus(F.) (Coleoptera: Bruchidae), and is the first study to make a direct, controlled comparison of the sterile male and genetic marker techniques to estimate sperm precedence.2P2values (the proportion of offspring fathered by the second male) obtained from the two methods were similar: P2(sterile male) = 0.82, P2(genetic marker) = 0.85. Both methods are therefore suitable for studying sperm precedence if the appropriate correction factors are applied.3The importance of general fertilization ability, differential fertilizing capacity and differential zygote mortality are examined and discussed.

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00191.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1Atypical of the parasitoid Hymenoptera, femaleGoniozus nephantidisMuesebeck remain with offspring until they pupate. This behaviour will only have evolved if the consequent reduction in fecundity is outweighed by fitness returns.2G.nephantidiscompetes for hosts with conspecific and non‐conspecific parasitoids. The effectiveness ofG.nephantidisat deterring superparasitism and multiparasitism is tested. Brood survivorships were compared whenG.nephantidisandBracon hebetorSay intrude on hosts with the mother present and absent and with offspring at different developmental stages.3Laying by the intruder reduced brood survivorship. Guarding reduced oviposition on unparasitized hosts by intruding females, and prevented superparasitism of hosts with egg broods. Hosts with larval broods were rarely superparasitized. Multiparasitism was common except on hosts with guarded larval broods, but even here survivorship was reduced.4Competitive asymmetries determined the outcome of contests for possession of host resources.5The costs of remaining seem at least partially offset by the prevention of oviposition by competing parasitoid

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00192.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1The oak treehopperPlatycotis vittata(Fabricius) is bivoltine throughout its range with discrete generations in the early spring and autumn. Females of both generations diapause.2Latitudinal variation in the timing of life history exists among four populations ofP. vittataalong the eastern coastal plain of the United States.3We disrupted synchronization betweenP.vittatalife history and host‐plant phenology in the springs of 1984 and 1985 by placing southern populations on northern trees with a different phenology. This caused some females to oviposit abnormally in late spring, without entering diapause. The offspring of these females had reduced reproductive success.4Winter diapause can be broken by providing females with a newly flushing tree with high levels of amino nitrogen in the sap. Females terminated winter diapause on trees breaking winter dormancy while females on trees still in winter dormancy did not, under identical photoperiod and temperature regimes.5The role of host‐plant mediated life history variation as a process promoting intraspecific geographic differentiation in the arboreal sap‐feeding guild is disc

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00193.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1Foragers of the ant speciesLasius pallitarsis(Provancher) andMyrmica incompletaProvancher were given access to two food patches that differed in nutritive quality. In about half of the trials, the higher quality patch also had a mortality risk for the foragers in the form of a largeFormica subnudaEmery ant located along the trail. Colonies were given access to the food for 4 or 24 h, every second day.2Use of the higher quality patch byL.pallitarsisforagers was depressed by the mortality risk. In contrast to the predictions of a food stress hypothesis, foragers used the risky patch more in the longer access trials. This appears due to a decline in the activity level of theF.subnuda, which results in a significantly lower mortality risk per trip.3M.incompfetaalso significantly decreased their use of the higher quality patch when aF.subnudawas present. However, the length of time a colony had access to the patches had no effect on the use of the risky patch.M.incompletaforaging behaviour seems relatively insensitive to short‐term food stress or changing levels of mortality risk.4The differences between species in their exploitation of patches and reactions toF.subnudaare discussed in terms of the species’natural hist

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00194.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1The relationship between parasitization byEdovum puttleriGrissell and density of eggs of the Colorado potato beetle,Leptinotarsa decemlineataSay (Coleoptera: Chrysomelidae), was studied on two spatial scales (eggs mass and 6 m2cage).2For both scales, rates of parasitism were generally inversely related to host density for periods ranging from 2 to 8 days after parasitoid release. Thereafter, parasitism became independent of host density.3The initial inverse‐density relationship and subsequent shift to density independence may result from several factors: (1) ambient temperatures, (2) the parasitoid's limited egg production, (3) differential times of exposure of egg masses to parasitoids, and/or (4) the parasitoid's patterns of host feeding and oviposition.4Although overall levels of parasitism were relatively low, total mortality ofL.decemlineataeggs (including nonviable and cannibalized eggs, and those killed by parasitoid feeding) in parasitized egg masses was consistently high (˜70–

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1991.tb00195.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY