ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01189.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1. Ovipositing females should choose egg‐laying sites which maximize the growth and survivorship of their offspring. Accordingly, they should avoid habitats with high densities of competitors and predators and should choose sites with adequate food. We tested experimentally the oviposition response of the mosquito,Culiseta longiareolataMacquart, to extra food and two species which are both potential competitors and predators of its offspring: conspecific larvae and green toad (Bufo viridis) tadpoles.2. We conducted the experiment in outdoor artificial pools where wildC. longiareolatafemales were presented with choices of all combinations of the presence or absence of: (1)C.longiareolatalarvae, (2)B.viridistadpoles, and (3) extra food (a mixture of ground fish food and mouse chow).3. Oviposition rates averaged approximately 4 times greater in response to extra food.4. The presence of the tadpoles, particularly later in the experiment when they were larger, caused a significant reduction (approximately 50%) in oviposition rate.5. We did not detect a statistically significant effect of conspecific larvae on oviposition habitat selection.6. Our results indicate thatCulisetafemales choose habitats for oviposition based on food availability. They also tend to avoid habitats containingBufotadpoles, presumably to avoid predation and/or competitio

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01190.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1. Spectral analysis of 66 years of locust swarm abundance data failed to reveal any significant cycles although the dominant cycle detected in a de‐trended series, adjusted to take account of a significant partial autocorrelation for a lag of 1 year, had a periodicity of 16 years.2. Although some estimates of the intrinsic rate of increase (r) of desert locusts are indicative of chaos, reconstructions of locust dynamics using response surface methodology (RSM) suggested exponential stability. This was also true for data for the West African Region alone and inclusion of rainfall data from the Sahel improved the significance of an RSM model for West Africa.3. The observed positive relationship between locust abundance and rainfall in West Africa confirmed the importance of rain; but the variance of the locust abundance also increased with rainfall, making rainfall alone a poor predictor. However, this heteroscedastic pattern was reproducible by a simple logistic model with a chaoticrand a variableK.This was not the case when a stable value forrwas used.4. The available data and current methodologies are insufficient to provide unequivocal conclusions on locust dynamics, which are complicated by phase changes and associated switches inrvalue

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01191.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1. The floret inspection by honeybeesApis mellifera ligusticaon inflorescences ofCarduus acanthoideswas studied in a natural patch. First‐day stage capitula were protected with a net hood against insect visits. The next day, the net hood was removed at the time of maximal nectar accumulation, allowing a bee to visit the inflorescence. Walking trajectories on the capitula, the number of florets inspected and the duration of the visit were recorded. After the bee's departure, the inflorescence was cut off and analysed in the laboratory to determine the presence or absence of nectar in each of its florets.2. Bees made inspection trajectories without a defined systematic pattern.3. The number of floret inspections performed represented a high percentage of the available florets (57.37 ± 2.81%; mean ± SE;n =8).4. The number of depleted florets coincided with the number of floret inspections.5. The number of times a floret is visited in a bee's trajectory is non‐random.6. Strategies that might account for this high foraging efficiency are disc

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01192.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1. A recently introduced treehole mosquito from Asia,Aedes albopictus, is spreading throughout eastern North America, especially in tyre‐refuse piles. Previous studies have identified inhibitory effects of larvae on egg hatch as a potential population regulatory mechanism withinAedes.Larva‐egg interactions may also occur between species. This experiment assesses the ability of larvae ofA. albopictusand two possible competitors in North America,A.triseriatusandA.aegypti, to suppress hatching of conspecific and congeneric eggs.2. We exposed eggs of each species to varying combinations of larval species and density for 24h and assessed subsequent hatch rates.Aedes albopictuseggs exhibited the lowest level of inhibition when exposed to high larval densities; moreover, at the lowest larval density they imposed the most intense interspecific hatch inhibition.3. Discretionary hatching in response to larval density may influence community composition by promoting the spread ofA.albopictus, perhaps even leading to its dominance within North AmericanAedescommunit

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01193.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1. The ecology of the eulophid parasitoidMelittobia australicaGirault was studied in the laboratory and field in Jamaica. Further field observations were conducted in Trinidad.2. The sphecid, mud‐daubing waspSceliphion assimile(Dahlbom) was the main host in Jamaica, but nineteen out of twenty‐two investigated species of sphecid, eumenid and pompilid wasps, and apid and megachilid bees were attacked in Jamaica and Trinidad. The nineteen susceptible hosts suffered an average of 23.6% mortality due toMelittobia.Resin is a totally effective deterrent, spaces within the nest less so.3. Laboratory studies onSceliphronhosts estimated that developmental survival was greatest at 26°C and 83% r.h., duration of development shortest at 32°C and 72% r.h., longevity of adult fliers greatest (>13 days) at<25°C and 80% r.h., and fecundity greatest (454 eggs/female) at 28°C and 90% r.h. A separate experiment gave a maximum fecundity of 461.4. At 27°C and 71% r.h. the duration of development (egg‐adult) in the laboratory was 13.1 days for males, 13.9 days for crawlers and 17.4 days for fliers.5. Field studies showed that developmental mortality was low, while laboratory studies revealed it to be density dependent, ranging from 13% at the lowest densities to 39% at the highest. Estimated mortality at field densities was ∼25% onSceliphron.6. Field estimates of fecundity gave a mean of 429.5 eggs/female onSceliphronbut are positively biased by superparasitism. Fecundity is probably reduced to about 346 eggs in the field and further to about 289 as a result of superparasitism. Other hosts generally reduced the parasitoid's fecundity, and this always occurs whenMelittobiabecomes a hyperparasite.7. Superparasitism in the field onSceliphronwas 2.3 females/host for crawler morph females, 1.2 females/host for jumper females and 1.2 females/host for flier females.8. A cyclic budget using log10K; values (Freeman, 1976) revealed that the effect of superparasitism (K0= 0.124), the physical environment (K0= 0.078), developmental mortality (K1= 0.125), and the loss to males (K2= 0.020) to be small, but losses of dispersing females (k3= 2.326) to be massive.9. The individual chance for the three female morphs of finding a new host are very different. For crawlers (which search the natal host nest) it is 0.034 (1 in 29), for jumpers (which search the host nesting site) it is 0.0098 (1 in 102) and for fliers (which seek distant host nesting sites) 0.0021 (1 in 485). Risk is thus directly proportional to distance travelled (cm, m and km). Morph production is related

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01194.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1. In central Japan,Drosophila curvicepsOkada and Kurokawa was collected in spring and autumn but not in summer at lowlands (alt. 500–1200 m), while it was collected only in summer at highlands (1500–2000 m). Experiments on its thermal tolerance suggested that summer heat at the lowlands and winter low temperatures at the highlands were adverse to this species. It is considered that this species escapes from these extreme temperatures by undergoing seasonal migration between the lowlands and the highlands. This species had no photo‐periodic diapause and bred at both lowlands and highlands.2.D.immigransSturtevant was less cold‐hardy but more heat‐tolerant thanD.curviceps.It is considered that this species is unable to overwinter outdoors at least in the study areas (i.e. alt. 500m or higher in central Japan) and its populations in these areas originate with migrants from warmer areas.3.D.albomicansDuda, a subtropical species, was less cold‐hardy but more heat‐tolerant than the above two species.4. Climatic adaptations and distributions of these species are discussed with reference to their ther

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01195.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1. Early abscission of mined leaves was an important mortality factor of aPhyllonorycterspecies (Lepidoptera: Gracillariidae) onSalix lasiolepisBenth. (Salicaceae). A larger percentage of mined leaves abscised early (34.4% in 1990; 24.5% in 1991), andPhyllonoryctersurvival was greatly reduced in these abscised leaves.2. Leaf‐mining byPhyllonorycterwas associated with increased early leaf abscission. An egg removal experiment demonstrated that leaf mining induced this increase in leaf abscission.3. The induction of early leaf abscission was dependent upon the timing of herbivory and simulated herbivory (mechanical damage). Early mechanical damage induced leaf abscission, late mechanical damage did not. Mines which expanded early were more likely to induce leaf abscission than mines which expanded more slowl

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01196.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.1. In studies of insect‐host plant interaction it is often suggested that insects preferentially colonize host plants (or sites within plants) on which their fitness is maximized (a positive covariance of preference and performance). This suggestion stems from the assumption that natural selection has driven the system toward optimal use of resources.2. Our study of the galling aphidSmynthurodes betaeWestw. demonstrates that the distribution of galls on leaves is not due to preference, and can be altered by manipulating the aphid arrival time or the shoot growth rate.3. We found no correlation between gall density and performance (aphid clone size) at different positions along the shoot.4. Because leaves on the growing shoot are not equally responsive to aphid stimulation, the colonizers have no choice but to settle on leaves that are at the right stage when they arrive.5.S.betaecolonizers did not discriminate between shoots of their host and a congeneric non‐host, on which their fitness is invariably zero.6. Synchronization between galler and host plant phenologies seems to be the key to the observed distribution of galls on the tree. The data give no support to the preference‐performance hypot

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01197.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:0307-6946    

DOI:10.1111/j.1365-2311.1993.tb01198.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY