bluuebunny/crossref_metadata_2025 huggingface dataset:
Density‐dependent egg dispersion in flowers of Silene vulgaris by the seed predator Hadena confusa (Noctuidae)
Authors: PETTERSSON MATS W.
Published: March 2008

Abstract.

Hadena moths drink nectar from, pollinate, and oviposit into the flowers of the genus Silene. In the gynodioecious Silene vulgaris (Moench) Garcke (Caryophyllaceae), eggs were laid by Hadena confusa (Hufn.) females both in male phase flowers, which could not be pollinated by the moth at the time of oviposition, and in female phase and female flowers that allowed pollination.

Flowers in which an egg had been laid had a lowered probability of receiving a second egg laid by another female during the same night.

The degree of flower discrimination by the moth with respect to the presence of eggs was positively correlated with the proportion of flowers containing eggs.

The oviposition behaviour of H.confusa is moulded by four factors: (1) a high probability of chosen male phase flowers later becoming pollinated by other moths, (2) the presence of conspecific eggs and risk for larval competition, (3) probability of presence of conspecific eggs also in neighbouring flowers, (4) capability of larvae to move to adjacent flowers.
Heterogeneity and density dependence in a field study of a tephritid‐parasitoid interaction
Authors: REDFERN M. , JONES T. H. , HASSELL M. P.
Published: March 2008

Abstract.

The spatial distributions of two tephritid flies (Urophora stylata (Fabricius) and Terellia serratulae L.) attacking thistle flower heads and the levels of parasitism from their associated parasitoid guilds were studied over a 7‐year period.

Using these data it is possible to seek both temporal, density dependent relationships between average levels of parasitism and host density per generation, and also any spatial patterns of parasitism contributing to stability that may be operating within the same field system.

Parasitism by the two most important generalist parasitoids of T.serratulae is a direct function of average T.serratulae density per year. There is little evidence of any stabilizing heterogeneity arising from the spatial distribution of parasitism within generations.

Temporal density dependence of Urophora stylata cannot be confirmed from the 7 years of study but there is evidence of spatial heterogeneity which may have an important effect on the dynamics of the host population.
Nectarivore foraging ecology: rewards differing in sugar types
Authors: WELLS HARRINGTON , HILL PEGGY S. , WELLS PATRICK H.
Published: March 2008

Abstract.

Honey bees, visiting artificial flower patches, were used as a model system to study the effects of sugar type (sucrose, glucose, fructose, and mixed monosaccharide), caloric reward, and floral colour on nectarivore foraging behaviour. Observed behaviour was compared to the predictions of various (sometimes contradictory) foraging models.

Bees drank indiscriminately from flowers in patches with a blue‐white flower dimorphism when caloric values of rewards were equal (e.g. 1M sucrose in both colours; 1 M sucrose versus 2 M monosaccharide of either type), but when nectar caloric rewards were unequal, they switched to the flower colour with the calorically greater reward.

In yellow‐blue dimorphic flower patches, on the other hand, bees did not maximize caloric reward. Rather, bees were individually constant, some to blue, others to yellow, regardless of the sugar types or energy content of the rewards provided in the two flower morphs.

The results suggest that optimal foraging theory (maximization of net caloric gain per unit time) is a robust predictor of behaviour with regard to the sugar types common to nectars; such optimal foraging is, however, limited by a superstructure of individual constancy.
The first parasitic Trichoptera
Authors: WELLS ALICE
Published: March 2008

Abstract.

A parasitoid habit is confirmed in larvae of an Australian micro‐caddisfly, Orthotrichia muscari Wells, being the first known incidence of this habit in the order Trichoptera.

Larvae of O.muscari are non‐specific parasites of pupae of other caddisfly species.

O.muscari is in an Australian/New Guinean/SE Asian species group in Orthotrichia, all members of which probably share the habit. Their larvae and pupae have atypical features that are interpreted as adaptations to their uncharacteristic niche.
Correlates of reproductive success among field colonies of Bombus lucorum: the importance of growth and parasites
Authors: MÜLLER CHRISTINE B. , SCHMID‐HEMPEL PAUL
Published: March 2008

Abstract.

In natural populations, colonies of bumble bees vary in many important life history traits, such as colony size and age at maturity, or the number and sex of reproductives produced. We investigated how the presence of parasites in field populations of the bumble bee Bombus lucorum L. relates to variation in life history traits and reproductive performance. A total of thirty‐six colonies was placed in accessible nest sites in the field and monitored at regular intervals throughout a season.

Among the life history correlates, early nest foundation was strongly associated with large maximum colony size, old age and large size at maturity, and this in turn with successful production of males and queens, as well as with the number of sexuals produced. Overall, reproductive success was highly skewed with only five colonies producing all the queens. Sixteen colonies failed to reproduce altogether.

The social parasite Psithyrus was abundant early in the Bombus colony cycle and preferentially invaded host nests with many first brood workers and thus disproportionately large size, i.e. those colonies that would otherwise be more likely to reproduce or produce (daughter) queens rather than males. To prevent nest loss, Psithyrus had to be removed soon after invasion. Therefore, the effects reported here can only be crude estimates.

Parasitoid conopid flies are likely to cause heavy worker mortality when sexuals are reared by the colonies. Their inferred effect was a reduction in biomass that could be invested in sexuals as well as a shift in the sex ratio at the population level resulting from failure to produce queens. We suggest to group the inferred correlates into ‘early events’ surrounding colony initiation and social parasitism, and ‘late events’ surrounding attained colony size in summer and parasitism by conopid flies. Our evidence thus provides a heuristic approach to understand the factors that affect reproductive success of Bombus colonies.
Host behaviour modification by the endoparasitoid Aphidius nigripes: a strategy to reduce hyperparasitism
Authors: BRODEUR JACQUES , McNEIL JEREMY N.
Published: March 2008

Abstract. 1. One possible component of successful parasitism by insect parasitoids is the reduction of predation and hyperparasitism through the modification of host behaviour.

2. Just prior to death, potato aphids, Macrosiphum euphorbiae (Thomas), containing diapausing larvae of the parasitoid Aphidius nigripes Ashmead have been shown to leave the host plant to mummify in concealed sites, while those parasitized by non‐diapausing individuals generally leave the aphid colony to mummify on the upper leaf surfaces.

3. The present study examines the within plant distribution of aphids and mummies containing non‐diapausing A.nigripes, and compares parasitoid survival among microhabitats under field conditions.

4. On potato, Solunum tuberosum L., a significant proportion of aphids were found on lower leaf surfaces, whereas mummies were usually on the upper surfaces, particularly in the apical stratum of the plant canopy.

5. In both field surveys and experimental manipulations, parasitoid survival was higher on the upper surface of apical leaves than in other microhabitats, due to lower levels of hyperparasitism and, to a lesser extent, lower predation. This suggests that the pressure exerted by natural enemies has influenced the evolution of host behaviour modification.
The effect of superparasitism on development of the solitary parasitoid wasp, Venturia canescens (Hymenoptera: Ichneumonidae)
Authors: HARVEY JEFFREY A. , HARVEY IAN F. , THOMPSON DAVID J.
Published: March 2008

Abstract.

The effects of superparasitism on the rate of development, adult size and mortality of Venturia canescens (Hymenoptera: Ichneumonidae) were investigated. Parasitoids were reared from third (L3) and fifth (L5) instars of one of its hosts, Plodia interpunctella (Lepidoptera: Pyralidae) containing one, two or four parasitoid eggs.

Superparasitism increased the development time of Venturia reared from both instars, but the developmental delay was more evident in wasps from L5 hosts.

The size of parasitoids from L3 hosts was unaffected by egg number, but wasps from both superparasitized L5 treatments were significantly smaller than those from singly parasitized hosts.

Parasitoid mortality was significantly higher in L5 than L3, but within instars did not differ significantly with egg number.

The results confirm that superparasitism may affect the fitness of both the adult female wasp and her progeny, and should therefore be incorporated into models of superparasitism as an adaptive foraging strategy.
Phenotypic variation in colour pattern and seasonal plasticity in Eristalis hoverflies (Diptera: Syrphidae)
Authors: HOLLOWAY GRAHAM J.
Published: March 2008

Abstract.

An examination of phenotypic variation in colour pattern was carried out on four Eristalis hoverfly species using museum material.

The amount of phenotypic variation varied substantially among the species with E.arbustorum being the most variable. The other species showed a wide colour pattern range but less variation within that range (E.abusivus and E.nemorum), or a narrow range of colour variation (E.horticola).

Sexual colour dimorphism was apparent in all four species, but most pronounced in E.abusivus and E.nemorum.

There were good phenotype‐season relationships shown by both sexes in all species, except for female E.abusivus and E.nemorum, with paler insects being more abundant during the warmer summer months.

Female, but not male, E.arbustorum collected at inland sites were on average paler than those collected at coastal sites. This observation is considered with respect to temperature during the developmental stages.

The function of colour plasticity in hoverflies is discussed with reference to the need to maintain optimal thermal conditions for activity.
Density‐dependent regulation of Aedes cantans (Diptera: Culicidae) in natural and artificial populations
Authors: RENSHAW M. , SERVICE M. W. , BIRLEY M. H.
Published: March 2008

Abstract.

Mortality and size variation (siphon length) in Aedes cantans larvae were examined in natural populations in northern England in 1989 and 1990.

Under crowded conditions, density‐dependent competition led to reduction in the size of both larvae and adults and increased larval mortality.

Larvae were also maintained in cages in the field at different densities. Results paralleled those for the natural populations in the ponds; larvae maintained at high densities showed increased mortality and reduced size.

Possible density‐dependent factors leading to mortality and size reduction include cannibalism and contact inhibition leading to food shortages.

The main density‐independent factor contributing to larval mortality was habitat desiccation.
Asymmetric competition in cattle dung between two species of Onthophagus dung beetle and the bush fly, Musca vetustissima
Authors: RIDSDILL‐SMITH T. J.
Published: March 2008

Abstract.

Competition in cattle dung pads between two dung beetles, Onthophagus ferox Harold and Onthophagus binodis Thunberg, and the bush fly, Musca vetustissima Walker, was investigated in laboratory experiments, to determine why spring fly abundance in the field did not fall following the introduction of O. binodis.

At low beetle densities, the number of eggs laid by each species was reduced by the second species. A similar amount of dung was buried by each species alone or by both together.

At high beetle densities O. binodis egg production was substantially affected by each additional O.ferox, but O.ferox egg production was not affected by each additional O.binodis. Asymmetric competition occurred because O.ferox buried more dung than O.binodis, and a greater proportion in day 1 (pre‐emptive dung burial).

O.ferox caused greater M. vetustissima egg‐puparia mortality than O. binodis. Mortality mostly occurred in young M. vetustissima larvae less than 1 day old. Total egg‐puparia fly mortality was correlated better with the dung buried on day 1 than dung buried on day 8 (pre‐emptive dung burial). O.binodis did not add to fly mortality by O.ferox at high densities because of asymmetric competition between the beetles.
The frequency of detection of density dependence in insect orders
Authors: HOLYOAK M.
Published: March 2008

Abstract.

A priori, there are no obvious reasons why patterns should exist in the frequency of density dependence across insect orders. However, orders may reflect related factors which influence population regulation (e.g. life‐history patterns and ecology) and are difficult to quantify. The frequency of occurrence of density dependence is compared in 171 time series (of ten or more generations) from Lepidoptera, Hemiptera, Diptera, Odonata, Hymenoptera and Coleoptera. A posteriori attempts are made to identify the cause of observed patterns.

Buhner's (1975) test found non‐delayed density dependence more frequently in Odonata than Lepidoptera and Hymenoptera, which in turn showed non‐delayed density dependence more frequently than Diptera, Hemiptera and Coleoptera. Similarly, detection was greater for Odonata than other orders using Dennis & Taper's (1993) test for density dependence and Crowley's (1992) test for attraction. Varley & Gradwell's (1960) test found density dependence less frequently in Hemiptera than other orders. These differences were independent of time series length, temporal trends and numbers of generations per year.

The reasons for observed patterns in detection of density dependence (and attraction) in insect orders are not clear; however, plausible explanations are differences in: (i) intrinsic growth rate, which is correlated with body size (although evidence to support this hypothesis is weak); (ii) the sampling method used; or (iii) whether individuals come from a single population or many populations.

Using Turchin's (1990) test, delayed (lag 2) density dependence was detected most frequently in Hymenoptera, which often show delayed diapause or are parasitoids.
Predation and parasitism in a tropical herbivore community
Authors: MEMMOTT J. , GODFRAY H. C. J. , BOLTON B.
Published: March 2008

Abstract.

Crawling predators were excluded from bamboos attacked by three species of chrysomelid leaf miner in two plots of tropical dry forest in Costa Rica.

The percentage of predated mines declined from an average of 61 % to an average of 29% in plots where crawling predators had been excluded. There were concomitant increases in successful beetle emergence and in the numbers of beetles attacked by parasitoids.

The probability of a miner that had escaped predation being attacked by a parasitoid was the same in experimental and control treatments, indicating that the risks of predation and parasitism are statistically independent.

The results were consistent across species and plots with the exception of one species in one plot where emergence was lower in the exclusion treatment than in the control because of very severe parasitoid attack. This result is unexplained.

Limited observations, and evidence from the type of damage observed on predated mines, suggest that the most important crawling predators are ants.
Overdispersion of Allothrombium pulvinum larvae (Acari: Trombidiidae) parasitic on Aphis gossypii (Homoptera: Aphididae) in cotton fields
Authors: ZHANG Z.‐Q. , CHEN P.‐R. , WANG K. , WANG X.‐Y.
Published: March 2008

Abstract.

Dispersion patterns of the protelean parasite, Allothrombium pulvinum Ewing, among individuals of an aphid host, Aphis gossypii Glover, were examined during spring 1991 in several cotton fields in Jiangsu Province, China.

The variance‐to‐mean ratios (i.e. dispersion index) of larval mites per host were greater than 1, indicating that the mite parasites were overdispersed among aphid hosts. The variance increased with the mean according to the power law, variance = 1.51 mean106, which explained 99.7% of the variation in the data.

The negative binomial distribution adequately describes the patterns of larval mite dispersion among aphid hosts in eight out of ten populations. The degree of clumping (1/k) decreased curvilinearly with parasite density (mites per host).

Mites were more clumped among adult aphids than among immature ones.

Ecological and evolutionary consequences of mite overdispersion within host populations are discussed. The role of Allothrombium in pest control is also discussed.
Diversity and faunistics of small moths (Microlepidoptera) in Bornean rainforest
Authors: ROBINSON GADEN S. , TUCK KEVIN R.
Published: March 2008

Abstract.

Samples of Microlepidoptera (including Pyraloidea) collected at light in mangrove forest, lowland mixed dipterocarp forest, and montane oak‐laurel forest in Borneo are compared.

Diversity (Williams' alpha) is very high in lowland forest, with a value of 414; it is lower, 226, in montane forest and very much lower, 47, at the edge of mangrove forest.

There is some evidence that apparent diversity increases with accumulation of samples.

Samples from the three forest types have very few species in common and come from separate assemblages.

Pyraloidea in samples taken 1km apart in lowland forest represent an assemblage common to the two sites but Microlepidoptera samples appear to represent slightly different assemblages.

There are no abundant species in lowland or montane forest: species with more than ten individuals comprised less than 4% of the samples. Four common species in mangrove forest accounted for 34% of the sample.

The proportion of Tineoidea, Gelechioidea and Pyraloidea is lower in montane forest than in lowland forest, while that of Yponomeutoidea and Tortricoidea is higher.

Just eight families of Microlepidoptera account for 90% of the species in samples from all three forest types.

The number of species of moths in Borneo is suggested to be in excess of 8500.
Efficient floret inspection by honeybees in capitula of Carduus acanthoides
Authors: GIURFA MARTIN , NÚÑEZ JOSUÉ A.
Published: March 2008

Abstract. 1. The floret inspection by honeybees Apis mellifera ligustica on inflorescences of Carduus acanthoides was 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 discussed.
The community ecology of Aedes egg hatching: implications for a mosquito invasion
Authors: EDGERLY JANICE S. , WILLEY MICHELLE S. , LIVDAHL TODD P.
Published: March 2008

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 within Aedes. Larva‐egg interactions may also occur between species. This experiment assesses the ability of larvae of A. albopictus and two possible competitors in North America, A.triseriatus and A.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 albopictus eggs 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 of A.albopictus, perhaps even leading to its dominance within North American Aedes communities.
Effects of herbivory and genotype on growth and survivorship of sand‐dune willow (Salix cordata)
Authors: BACH CATHERINE E.
Published: March 2008

Abstract.

The response of different clones of sand‐dune willow, Salix cordata, to herbivory by a specialist herbivore, Altica subplicata, was studied in three glasshouse experiments. Plants were caged and exposed to three herbivory treatments: no beetles, low number of beetles, and high number of beetles.

Plants consistently had significantly higher growth rates in the absence of herbivory than under conditions of low or high herbivory (1.5–6 times higher).

Herbivore treatment influenced mortality from drought stress; more plants from the low and high herbivory treatments (40% and 80%) died from drought stress than did control plants (0%).

Clone genotype significantly influenced growth rates and the susceptibility of plants to drought stress. However, clones showed similar growth responses to herbivory, suggesting a lack of genetic variation in tolerance or resistance to herbivory.
Effects of extended and repeated exposures to low temperature on mortality of the peach‐potato aphid Myzus persicae
Authors: HOWLING G.G. , BALE J.S. , HARRINGTON R.
Published: March 2008

Abstract.

The survival of adult and first‐instar Myzus persicae reared at 20°C and 10°C was investigated after brief (1 min) exposure in the absence of plant material to temperatures between −5°C and −25°C, and extended exposures on plants of 1–10 days at a constant 5°C, 3°C and −5°C and a 24 h cycling regime between 5°C (18 h) and −5°C (6 h).

Life stage, rearing temperature, period of exposure and temperature regime all had a significant effect on the ability of aphids to survive cold. The effects of life stage and rearing temperature were most noticeable following exposure to cycling temperatures and extended exposures at −5°C, and least apparent after 1 min exposures at lower sub‐zero temperatures.

Mortality following exposure to temperatures cycling between −5°C and 5°C was greater than that at 3°C (the mean of the cycling temperatures) and less than at a constant −5°C, suggesting that when temperatures fluctuate by a few degrees around 0°C the minimum temperature may affect survival to a greater extent than the mean.

These results suggest that an overwintering population of acclimated M.persicae would persist without significant mortality after a period of 7–10 days with −5°C frosts each night.
Host‐plant influence on the population ecology of the jack pine budworm, Choristoneura pinus (Lepidoptera: Tortricidae)
Authors: NEALIS V. G. , LOMIC P.V.
Published: March 2008

Abstract.

Newly‐emerged, second‐instar jack pine budworm (Choristoneura pinus Freeman) establish spring feeding sites preferentially in the pollen cones of their host tree, Pinus banksiana Lamb.

Laboratory studies showed that the rate of establishment and survival of jack pine budworm on pollen cones was high throughout the entire spring emergence period of the insect.

In contrast, the rate of establishment and survival of jack pine budworm on vegetative buds was very poor early in the spring. Vegetative buds were only acceptable as feeding sites to the jack pine budworm for a relatively brief period in late spring.

Field studies showed that the change in population density of jack pine budworm during the spring emergence stage, as expressed by k‐values, was a function of the abundance of pollen cones in the stand. Population reduction was greatest in those stands with the fewest pollen cones.

Direct measurement of spring dispersal by jack pine budworm showed that dispersal and consequent losses to the budworm population were greatest in stands with the fewest pollen cones.

We conclude that changes in the density of jack pine budworm are strongly influenced by production of pollen cones in the host stand. Because pollen cone production is related to previous years of defoliation by the jack pine budworm, we propose that pollen cones act as a density‐dependent factor governing the density of early‐stage jack pine budworm.

The resulting dynamics are compared to those of other budworm species and used to explain observed regional and temporal patterns of jack pine budworm outbreaks.
Alternative seed defence mechanisms in a palo verde (Fabaceae) hybrid zone: effects on bruchid beetle abundance
Authors: SIEMENS DAVID H. , RALSTON BARBARA E. , JOHNSON CLARENCE DAN
Published: March 2008

Abstract.

We asked three questions about the patterns of relative abundance of insect herbivores across host plant taxa at a palo verde hybrid zone. (1) What is the morphological structure of the hybrid zone and does this suggest a certain pattern of introgression? (2) How are putative parental seed defence mechanisms expressed in hybrid plants? (3) Do ovipositing females prefer host plant taxa on which their offspring have best survivorship?

Morphologically, hybrids were either intermediate or tended to resemble one parental species. Previous studies have suggested that unidirectional introgression results in loss of parental defence mechanisms against herbivores. Hybrid plants in general lacked seed coat resistance and early pod abscission which are known to act as plant defence mechanisms against bruchid beetles in the parental palo verde trees.

All other sources of bruchid mortality that we examined did not vary across parental and hybrid taxa, with the possible exception of egg parasitism which occurred at a lower frequency on one parental palo verde species.

Thus, survivorship of bruchid offspring should be greater on hybrid palo verdes.

Patterns of egg densities suggested that females may prefer hybrid hosts in some years but not others. An oviposition choice experiment conducted in the field, however, showed bruchids have no preference for hybrids over one of the parental species.

These results suggest that some insect herbivores may have higher densities on hybrid host plants because they are less resistant.
Influence of inter‐tree variation in time of budburst of white spruce on herbivory and the behaviour and survivorship of Zeiraphera canadensis
Authors: QUIRING DAN T.
Published: March 2008

Abstract.

Field studies were carried out during 4 years to determine the effects of inter‐tree variability in the time of budburst of white spruce, Picea glauca Moench (Voss.), on the distribution, behaviour and survivorship of, and herbivory by, the spruce bud moth, Zeiraphera canadensis Mutt. & Free.

Differences between trees in herbivory, bud moth density and survivorship were inversely related to the mean date of budburst. The most and least susceptible half‐sib‘families’evaluated were the first and last to flush, respectively. Differences in herbivory for trees in two families with similar phenologies were partially due to oviposition preference.

Oviposition and larval survivorship were highest on trees in the most susceptible families. Although egg hatch was more closely synchronized with budburst in warm than in cool springs, between tree differences in the time of budburst were consistent over years.
Coastal insect herbivore populations are strongly influenced by environmental variation
Authors: STILING PETER
Published: March 2008

Abstract.

Pissonotus quadripustulatus is a brachypterous planthopper that feeds on the clonal salt marsh plant, sea oxeye daisy, Borrichia frutescens. Asphondylia borrichiae is a macropterous gall fly that creates galls on the apical meristems. Most Borrichia occurs in isolated patches consisting of more than one genotype.

Densities of Pissonotus and Asphondylia do not significantly differ within patches but they do differ between patches. I tried to find out why some patches of Borrichia support consistently higher densities of Pissonotus and Asphondylia than others.

Reciprocal transplants of Borrichia between patches showed that for both Pissonotus and Asphondylia recipient site (local environment) had a strong effect on population densities. However, the best sites for Asphondylia were generally the worst sites for Pissonotus and vice versa.

Donor site (local plant genotypes) was not significant for Pissonotus but was marginally significant for Asphondylia. However, for Asphondylia recipient site had a greater effect. Local plant genotype effects may be greater for gall‐forming insects, which tend to be specialists, than for more generalist sapsucking insects.
Within‐tree and among‐tree variation in growth of Epirrita autumnata on mountain birch leaves
Authors: SUOMELA JANNE , NILSON ANNA
Published: March 2008

Abstract.

We studied among‐tree and within‐tree variation in the growth of larvae of a geometrid, Epirrita autumnata, on mountain birch (Betula pubescens ssp. tortuosa) leaves at different hierarchical levels: among trees (genets), among ramets within trees, among branches within ramets, among shoots within branches and among leaves within shoots. We used only short shoot leaves, which burst simultaneously in spring.

Trees accounted for most of the variation in larval growth rate, but there was substantial variation also among ramets within trees, among branches within ramets, and among short shoots within branches. Variation among leaves within short shoots was negligible. When the probabilities from different experiments were combined, the differences were statistically significant at the tree, ramet and branch levels, and approached significance at the shoot level.

In different experiments, larval growth was from 9% to 54% lower on the worst tree than on the best tree of the experiment. On average, larval growth rate was in different experiments from 11% to 32% lower on the worst ramet than on the best ramet within tree, from 8% to 18% lower on the worst than on the best branch within ramet, and from 12% to 30% lower on the worst than on the best shoot within branch.

The amount of among‐and within‐tree variation shown by our results may have ecological and evolutionary implications: among‐tree variation should select for discrimination by ovipositing females and dispersing larvae, within‐tree variation should select also for optimal foraging behaviour of larvae.
Energy budget of swarming male mosquitoes
Authors: YUVAL BOAZ , HOLLIDAY‐HANSON MERRY L. , WASHING ROBERT K.
Published: March 2008

Abstract.

The objective of this study was to determine, in the field, the energetic costs of swarming for male Anopheles freeborni (Diptera: Culicidae). By comparing the caloric contents of resting males to marked males captured after swarming, we established when sugar feeding takes place, what energy source is used to fuel swarming flight, and how much energy is invested in this activity.

Sugar‐feeding takes place sometime during the night after swarming is concluded. Nectar sugars are therefore not immediately available to fuel flight. Stored sugars (trehalose and glucose) and glycogen are the primary sources of energy for flight. Lipids are not used to fuel flight but may be used in resting metabolism.

Male size is not related to feeding success. For males of all sizes, swarming consumes more than 50% of available calories. Accordingly, the ability of an individual to find and exploit nectar sources will greatly affect reproductive success.
Activity patterns of females of the solitary bee Anthophora plumipes in relation to temperature, nectar supplies and body size
Authors: STONE GRAHAM N.
Published: March 2008

Abstract.

Patterns of activity at a large nesting aggregation and at foraging sites are described for females of the solitary bee Anthophora plumipes (Pallas). Changes in the quality and quantity of the resource collected by females provisioning cells are related to variation in female body mass and microclimate.

Activity at the nest site demonstrated relationships with aspects of the thermal environment experienced by A.plumipes. Measures of temperature showing significant relationships differed for females in different stages in the nesting cycle exhibiting characteristically different behaviour patterns.

Larger females emerged from nest tunnels earlier in the morning and provisioned cells at lower ambient temperatures than smaller individuals. Body size therefore predicts reproductive success at low ambient temperatures.

Pollen and nectar loads carried by females increased with ambient temperature. Because only one cell is completed per day and the size of offspring is determined by the quality and quantity of resource provided by the mother, the body size of individuals emerging in the following season will depend on interactions between climate and body size, in addition to any heritable component.

Variation in activity levels at foraging sites is attributed not only to thermal considerations, but also to variation in the quality of rewards available at different floral sources.
The effects of crop diversification on herbivorous insects: a meta‐analysis approach
Authors: TONHASCA ATHAYDE , BYRNE DAVID N.
Published: March 2008

Abstract.

We used a meta‐analysis to evaluate the hypothesis that diversified crops are subject to lower density of herbivorous insects. This method consists of integrating findings of independent studies by calculating the magnitude of treatment effects (effect size).

A literature review covering a period of over 10 years yielded twenty‐one studies that contained sufficient information for the meta‐analysis. The data were analysed according to three criteria: yearly replications of the same study were considered independent data so that research repeated over time would have greater weight; a second meta‐analysis was conducted with results of only 1 year because of possible lack of independence between results of the same study; the third approach was to remove studies involving Brassica spp. from the analysis because they are redundant from the standpoint of testing a general hypothesis of crop diversification.

The three analyses resulted in effect sizes of 0.50, 0.35 and 0.27, respectively, and all were statistically significant. These results correspond to 69%, 63% and 60% differences between average insect densities for treatment (diversified crops) and control groups.

We considered the last criterion for data analysis as the most appropriate because of lowest bias from non‐independence between samples. Therefore we concluded that crop diversity caused moderate reduction of herbivorous insect populations.

The implications and limitations of meta‐analyses are discussed.
Intraspecific variability in host plant quality and ovipositionaI preferences in Eucheira socialis (Lepidoptera: Pieridae)
Authors: UNDERWOOD DESSIE L. A.
Published: March 2008

Abstract.

This study investigates interactions between Eucheira socialis (Pieridae: Lepidoptera), a strict monophagous herbivore, on Arbutus xalapensis (Ericaceae), a host plant with few herbivores. This tight association of insect on plant has many attributes conducive to reciprocal rather than diffuse evolution.

An indirect way of testing plant–insect coevolutionary theories is to test for the necessary conditions for reciprocal evolution in ecological time. Two conditions for coevolution were studied: (1) host plants vary in their suitability for larval growth and development, and (2) ovipositing insects discriminate among these plants based on their relative suitability.

Large differences in host plant suitability were found and relative differences were consistent from year to year.

There was no evidence that female insects based their ovipositional decisions on relative tree quality, which implies that factors other than host plant quality are involved in the maintenance and evolution of oviposition behaviour in Eucheira.

Of seven factors known to influence ovipositional preferences of insects among plants independent of potential larval success, the most likely causal factor in this system is the ability of females to balance a time/energy budget for finding potential oviposition sites, discriminating among them, and actually ovipositing.
Seasonal polyphenism in the wild: survey of wing patterns in five species of Bicyclus butterflies in Malawi
Authors: WINDIG JACK J. , BRAKEFIELD PAUL M. , REITSMA NICO , WILSON JOHN G. M.
Published: March 2008

Abstract.

For three successive years Bicyclus butterflies were caught on a daily basis at a field site in Malawi.

Over 5000 butterflies, belonging to five species, were captured. Eight characters describing their plastic wing pattern were measured and analyzed.

Broadly speaking, the plasticity is similar for all species, with the wet season forms having conspicuous wing markings (e.g. eyespots), and dry season forms lacking these markings.

However, at a more detailed level, each species has its own specific form of plasticity with especially clear differences in the number of intermediate forms.

Females generally show a higher degree of plasticity than males.

The relative frequencies of intermediate forms and the difference between the sexes are associated with differences between the species in their preference for more open habitats or forests.

The species with the most divergent plasticity is also ecologically and phylogenetically comparatively distant from the others.
Sex‐ratio bias in an aphid parasitoid‐hyperparasitoid association: a test of two hypotheses
Authors: MACKAUER M. , LARDNER R. M.
Published: March 2008

Abstract.

We tested the hypothesis that biased sex ratios in the aphidiid parasitoid, Aphidius ervi, are the result of sex‐specific mortality of immatures due to hyperparasitism. The solitary hyperparasitoid, Dendrocerus carpenteri, deposits its eggs on the prepupa or pupa of the primary parasitoid after its pea‐aphid host is mummified.

In dichotomous choice tests, females of D.carpenteri accepted immatures of both sexes of A.ervi with equal frequency. Independent of the sex of the primary parasitoid, the probability of a mummified pea aphid being hyperparasitized did not differ between large (adult at the time of death) and small (fourth nymphal instar) mummies.

As predicted by‘host quality’models of offspring sex allocation, D.carpenteri produced a higher proportion of female than male offspring in large mummies. These laboratory results were supported by field data.

Because hyperparasitism by D.carpenteri is random with regard to host sex, it should have no influence on optimal sex allocation by the primary parasitoid.
Bloodmeal evacuation from the midgut of Glossina pallidipes in relation to tsetse foraging activity and trappabiIity
Authors: MADUBUNYI L. CHUKA
Published: March 2008

Abstract.

Foraging for bloodmeals is the most frequently recurrent and probably the most targetable of all activities that render tsetse vulnerable to interception with static trapping devices.

Surgical monitoring of the rnidgut every 24 h during three successive days of food deprivation, showed that a full bloodmeal, irrespective of its size or source, vacated the rnidgut of both sexes of Glossina pallidipes Austen in eight progressive stages.

Probing responsiveness in both sexes increased exponentially during the first four stages of their midgut evacuation, reaching a peak between stages 3 and 5. Thereafter it decreased, also exponentially.

Most G.pallidipes caught by NG2G traps baited with cow urine and acetone had midguts in the last three stages (6–8) of bloodmeal evacuation. The same was true of the majority of those that failed to feed on a calf shortly after entrapment.

The implications of the foregoing for tsetse foraging activity and trappability as well as for the potency of cattle urine and acetone as odour‐bait for tsetse are discussed.
Dynamics of parasitism in the organ‐pipe wasp, Trypoxylon politurn: effects of spatial scale on parasitoid functional response
Authors: MOLUMBY ALAN
Published: March 2008

Abstract.

Life tables and rates of parasitism were tabulated from mud nests built by Trypoxylon politum (Hymenoptera: Sphecidae) at nine different nesting sites from Missouri and Mississippi.

Most developmental mortality occurred either during the first two instars of development, or during the inactive prepupal phase. The majority (76%) of deaths were caused by insect parasitoids and cleptoparasites. Levels of parasitism and survivorship varied among nesting sites, and among locations within the two sites surveyed at a fine spatial scale.

Total developmental mortality, K, was positively associated with the number of hosts (immature T.politum) per site. Within one of two sites sampled at a fine spatial scale, K was negatively associated with the local density of hosts. Levels of total parasitism were positively associated with host population size, and negatively associated with local host density within one of the two sites sampled at a fine spatial scale.

Levels of parasitism by Melittobia (Hymenoptera: Eulophidae) were positively associated with the number of hosts per site, but negatively associated with the local density of hosts within sites. Melittobia parasitism was also negatively associated with the local density of old nesting material within sites.

Parasitism by Melittobia was a function of both the numbers of nests per quadrat and the mean nest size per quadrat at one of the two sites surveyed at a fine scale. At the other site, parasitism by Melittobia was a function of mean nest size per quadrat.

The life cycle and nesting behaviour of T.politum, in relation to the regulation of its numbers, is discussed.
Foraging and courtship behaviour in males of the solitary bee Anthophora plumipes (Hymenoptera: Anthophoridae): thermal physiology and the roles of body size
Authors: STONE GRAHAM N. , LODER PHILIP M. J. , M.BLACKBURN TIM
Published: March 2008

Abstract.

The effects of climate and body size on male behaviour were examined in the solitary bee Anthophora plumipes (Hymenoptera: Anthophoridae), which shows resource‐based polygyny at floral food sources in Britain in spring.

Larger males are able to fly at lower temperatures than smaller males, and can therefore court females under conditions in which smaller males cannot fly. This is predicted from patterns of endothermic ability at low temperatures already demonstrated within this species.

Video analysis of male competition for opportunities to initiate courtship with tethered females showed that larger males are also competitively superior, and can displace smaller males from favoured flight positions immediately behind females.

The mating system shown by male A plumipes is strongly dependent on male density. At low densities, males show exclusive territoriality at floral sources. As male density increases, this strategy is abandoned in favour of patrolling with considerable spatial overlap between males, and opportunistic Polygyny.

Despite high endothermic abilities, male behaviour is highly dependent on weather, and particularly ambient temperature. Males bask in the early morning and maintain high thoracic temperatures. Temperature data from freshly killed bees show that thoracic warming from solar sources effectively doubles the thermogenic power generated by the bee alone at low ambient temperatures.

Male strategies in A.plumipes are compared to female responses to climate. Having controlled for differences in body size there is no difference in endothermic abilities between the sexes. Males do not, however, fly under conditions in which females of the same size would remain active. These results are discussed in the light of differential dependence of reproductive success on flight activity for the two sexes.
Correlates of male mating success in two natural populations of the damselfly lschnura graellsii (Odonata: Coenagrionidae)
Authors: CORDERO A.
Published: March 2008

Abstract.

Two natural populations of Ischnura graellsii were studied in north‐west Spain by means of mark‐release‐recapture techniques. Recaptured males were a random sample of the original marked population with regard to date of marking. At O Rosal a greater proportion of young males than old males disappeared after marking; at Lourizán recaptured males were larger than unrecaptured ones.

The number of matings observed in both populations showed great daily variation. Most of the variation is accounted for by climatic variables. Most males (56–65%) and many females (41–45%) were never observed to mate.

Male LMS was highly correlated with lifespan in both populations. At O Rosal, male LMS was also positively correlated with body length, and mated males were larger than unmated males. This surprising result for a non‐territorial species was due to the positive correlation between date of marking and size. There was a positive correlation between body size and mobility for males at O Rosal, but mobility was not correlated with male LMS.

As predicted by sexual selection theory, the standardized variance in male LMS was greater than in female LMS. Variation in mature lifespan explained 16% of variance in male LMS at Lourizán and 28% at O Rosal.
Flexible patch time allocation by the leafminer parasitoid, Opius dimidiatus
Authors: NELSON J. M. , ROITBERG B. D.
Published: March 2008

Abstract.

The ability to use flexible decision rules can be an advantage to parasitoid females searching for patchily‐distributed hosts. In a series of laboratory experiments the hypothesis that Opius dimidiatus, a solitary parasitoid of the chrysanthemum leafminer (Liriomyza trifolii), adjusts the time she allocates to searching for her larval hosts in response to both patch qualities and experiences with hosts was tested by varying such patch parameters as area, presence of host mines and density of host mines, and by allowing ovipositions and encounters with parasitized hosts.

Though leaf area was not a factor, the presence of host mines in a leaf did increase the time a female O.dimidiatus spent searching, over time spent on unmined leaves.

When host mine density was increased, females responded by increasing their search period in a density‐dependent manner, suggesting a perception of patch quality.

Ovipositions in hosts caused females to reset their‘giving‐up time’(GUT), or increase search intensity, by adding an amount of search time that increased with each successive oviposition. Conversely, encounters with parasitized (unsuitable) hosts incremented the GUT, but by an amount that decreased with each successive encounter.
Nocturnal activity and resource utilization in the aphid hyperparasitoid, Dendrocerus carpenteri
Authors: VOLKL WOLFGANG , KRANZ PETRA
Published: March 2008

Abstract.

Females of the aphid hyperparasitoid Dendrocerus carpenteri (Curtis) search successfully for hosts during both day and night. Oviposition numbers per host patch did not differ significantly between day and night.

D.carpenteri females also displayed a nocturnal flight activity, showing that they are not only capable of searching on a given host plant but also of dispersing between host plants.

Nocturnal oviposition activity was mainly influenced by egg load. Females with a high egg load laid more eggs at night than females with a comparatively low egg load. Thus, D.carpenteri females may use nocturnal foraging to compensate for the lack of oviposition opportunities during day.

D.carpenteri females which foraged continuously for hosts both day and night (= for 24 h per day) benefitted from an 1.4‐fold increase in lifetime reproductive success when compared to females which foraged only by day (= for 16 h per day).

The benefit of night foraging for this species is a significantly increased reproductive success.