bluuebunny/crossref_metadata_2025 huggingface dataset:
Life‐history responses of larviparous Boettcherisca formosensis (Diptera: Sarcophagidae) to larval competition for food, including comparisons with oviparous Hemipyrellia ligurriens (Calliphoridae)
Authors: SO PING‐MAN , DUDGEON DAVID
Published: March 2008

Abstract. 1 The effect of larval rearing density on life‐history parameters of Boettcherisca formosensis Kirner & Lopes (Sarcophagidae) was investigated. Increases in rearing density resulted in lowered larval survivorship, shortened larval development time and production of smaller, shorter‐lived adults with reduced fecundity.

2. B. formosensis is larviparous. Average brood size was 17.5±1.0 (mean±M) larvae, which was much less than the average number of mature larvae inside gravid females. Females apparently produced a series of small broods, distributing their offspring over a number of carcasses.

3. Compared with the oviparous species Hemipyrellia ligurriens (Wiedemann) (Calliphoridae), B. formosensis adults were larger and longer‐lived, with a longer larval development time but shorter larval feeding period. However, females had a shorter pre‐reproductive period, were less fecund, and had a lower life time reproductive investment.

4. B. formosensis had lower relative performance (measured by the composite index of performance, r') than H. ligurriens over the larval rearing density range, and was more sensitive to increases in density. Although the r' values suggest that the sarcophagid may be a competitively inferior species, other features which are not included in the index (such as larvipary, short larval feeding period and spreading of offspring from a single brood among carcasses) may be of significant adaptive value to B. formosensis.
Oviposition and host‐feeding patterns in Aphelinus asychis (Hymenoptera: Aphelinidae) at different aphid densities
Authors: BAI B. , MACKAUER M.
Published: March 2008

Abstract. 1. The patterns of host‐feeding and oviposition were examined in Aphelinus asychis Walker, which had been provided with second‐instar pea aphids as hosts.

2. Female wasps responded to increasing host density (between one and forty aphids for 24 h) with an increasing tendency to oviposit rather than to feed. Superparasitism occurred at all aphid densities, even when unparasitized aphids were available.

3. Aphids intended for feeding were paralysed and died. Wasps did not feed on and oviposit in the same aphid.

4. Feeding to satiation lasted between 4 min and 42 min. Females that had starved for ≰18 h generally deposited one or more eggs before feeding again, while the reverse was true in wasps that had starved for 21 h.

5. The host‐feeding behaviour of A. asychis is determined by a female's nutritional status. At low rates of host encounter, the anhydropic eggs may be resorbed. This reproductive strategy conforms to the destructive non‐concurrent type among the Hymenoptera.
Choice of host plant as a factor in reproductive isolation of the aphid genus Cryptomyzus (Homoptera, Aphididae)
Authors: GULDEMOND J. A.
Published: March 2008

Abstract. 1. Host plant preference experiments were conducted with closely related taxa of the aphid genus Cryptomyzus. Males, and presexual morphs (sexuparae and gynoparae), were used to determine the impact of host plant choice on reproductive isolation. In the case of host‐alternating species these morphs are migratory and so will select the host plant.

2. Host plant preference of two closely related taxa of C. alboapicalis (Theobald) was found to promote their reproductive isolation. The preference of sexuparae of these monoecious taxa was more pronounced than that of the males.

3. Host plant preference and subsequent production of oviparae showed that C. galeopsidis (Kaltenbach) consists of two host races restricted to Ribes rubrum L. and R. nigrum L., respectively. The existence of clones, intermediate in their preference and reproductive performance on these plants, suggests that hybridization occurs.
Mechanisms of predator accumulation in a mixed crop system
Authors: LETOURNEAU D. K.
Published: March 2008

Abstract. 1. In a previous study, Orius tristicolor (White), a generalist predator of soft‐bodied insects and mites, invaded patches with a mixed plant assemblage at a faster rate than it did single‐species stands. This study was designed to determine experimentally the underlying mechanisms of predator movement patterns that cause more intense colonization of crop mixtures.

2. Plots were established in a randomized complete block design. Treatments reflected different components of mixed crop patches: species richness, plant density, colour contrast, structural complexity, and volatile plant compounds.

3. O. tristicolor colonists were more abundant on squash intercropped with corn and cowpea than in squash monocultures even though early season prey densities were similar. Initial accumulation of the generalist predator was also higher in densely planted monocultures and in monocultures with artificially enhanced structural complexity than in normally‐spaced squash monocultures.

4. Therefore, mechanisms underlying rates of predator colonization in a stand initially depended upon aspects of plant architecture and density and were independent of prey density and plant diversity. O. tristicolor densities at the end of the colonization period, however, were greater on squash (Cucurbita pepo L.) in polyculture than in any other treatment.

5. These results suggest that attributes of the vegetation can influence the colonization rates of interacting organisms on different trophic levels and thus can alter predator‐prey interactions and the development of community structure.
Intraspecific aggression, colony identity and foraging distances in Sudanese Microtermes spp. (Isoptera: Termitidae: Macrotermitinae)
Authors: PEARCE MICHAEL J. , COWIE ROBERT H. , PACK ANGELA S. , REAVEY DUNCAN
Published: March 2008

Abstract. 1. Intraspecific aggression between termite major workers was used to obtain estimates of foraging distances for three Microtermes species in Sudan.

2. Maximum foraging distance recorded for M. sp. nr albopartitus (Sjöstedt) in Khartoum was 11.3 m, giving an estimated minimum colony area of 100 m2. This is probably an underestimate. In the Tokar Delta, individuals from single colonies of M. najdensis Harris were encountered up to 42 m apart, giving a colony area of 1390 m2.

3. Intraspecific aggression could not be used reliably to distinguish members of different colonies of M. lepidus Sjöstedt. Soil barrier formation between groups of workers in petri dishes may be of use as a supplementary technique, especially for species showing no clear aggression.

4. Experiments on isolated laboratory colonics of M. sp. Nr lepidus Sjöstedt, established from alates collected in Khartoum, further confirmed the value of inter‐colony aggression for indicating colony identity.

5. The complications introduced into estimation of subterranean termite foraging areas by overlap and interdigitation of colonies are discussed.
Plant water stress and gall formation (Cecidomyiidae: Asphondylia spp.) on creosote bush
Authors: WARING GWENDOLYN L. , PRICE PETER W.
Published: March 2008

Abstract. 1. Populations of creosote bush (Larrea tridentata (DC) Coville), were studied in Arizona to determine whether associated gallformers (Cecidomyiidae: Asphondylia spp.) were more abundant on water‐stressed or nonstressed plants. Gall densities were measured along a steep elevational gradient that extended from mesic, higher elevations to lower elevations in the desert; and in the Grand Canyon where severely water‐stressed and relatively unstressed plants occurred adjacently. At the Grand Canyon site, the responses of creosote bush to water stress were also studied.

2. The number and densities of Asphondylia species increased both at lower elevations and locally on water‐stressed plants in the Grand Canyon, indicating that climatic and local conditions influence gallformer abundance in the same way.

3. Five of the eight Asphondylia species studied at the Grand Canyon site were more abundant on stressed plants, two species were more abundant on nonstressed plants and one species showed no preference for either plant type.

4. Densities of most species on stressed plants were positively correlated with the number of meristematic terminals per branch, which were more numerous on stressed plants, due to a bushier architecture. Flower gallformers were more abundant on nonstressed plants, which produced more flowers. Gall densities did not correlate with chemistry measurements, although these parameters also varied with level of stress.

5. These results suggest that gallforming species respond variably to plant stress, even within a closely‐related lineage, and that there are effects of stress on plants, including architectural changes, that may be more important to herbivores than biochemical effects emphasized by White (1984) and others.
Diel changes in forager size, activity, and load selectivity in a tropical leaf‐cutting ant, Atta cephalotes
Authors: WETTERER JAMES K.
Published: March 2008

Abstract. 1. The leaf‐cutting ant Atta cephalotes (L.) in a Costa Rican tropical moist forest showed diel changes in foraging activity. In most colonies studied, foraging was primarily nocturnal, although in a few colonies it was primarily diurnal.

2. In all colonies studied, mean forager mass was larger at night than during the day.

3. At night, most foragers carried freshly cut leaf fragments, whereas during the day a large proportion carried dried fragments and other vegetable matter collected from along their trail.

4. Along one trail, where foraging was primarily nocturnal, the match between ant mass and load mass was compared for laden ants at night and during the day. Laden ants at night were larger, carried relatively heavier loads, and showed a higher degree of matching between their mass and load mass than those foraging during the day.

5. A comparison of load masses of ants coming down a local tree and of ants picking up marked fragments from along their trail suggested that the diel difference in load mass and in the match between ant mass and load mass were related to the greater proportion of ants carrying freshly cut leaf fragments at night. Fresh fragments weighed more due to higher water content, and the match between ant mass and load mass was greater for ants cutting fresh fragments than for ants picking up abandoned fragments from along their trail.

6. Possible explanations for the diel changes in forager size and activity are discussed.
Predation of the cereal aphid Sitobion avenae by polyphagous predators on the ground
Authors: WINDER LINTON
Published: March 2008

Abstract. 1. Polyphagous predator densities were manipulated in a wheat crop using polythene exclusion barriers.

2. The rates at which aphids fell to the ground and subsequently climbed and returned to the crop canopy were measured.

3. Peak aphid density was highest when polyphagous predator density was lowest.

4. Similar rates of aphid fall‐off were measured in each plot, but aphid climbing rate was highest when predator densities were lowest.

5. It was concluded that ground‐zone predators reduced the rate at which aphids return to the crop canopy.
Characterization of terrestrial insect communities using quantified, Malaise‐trapped Coleoptera
Authors: HUTCHESON JOHN
Published: March 2008

Abstract. 1. Weekly samples of Malaise trapped Coleoptera from regenerating shrubland and an adjacent mature, podocarp‐broadleaved forest, in the North Island, New Zealand, were compared over one season. Three traps were monitored in each site.

2. Diversity indices did not group samples by site whereas the divisive polythetic classification analysis TWINSPAN showed that the two sites possessed clearly different communities. In the classification, site was of primary importance, with time of year, and trap position within site of secondary and tertiary importance respectively.

3. Samples were compared at different taxonomic levels and using different subsets of the database. Determination of the main families, morphotyped to species or species complex, was found to be sufficient to classify most samples to the appropriate community group.

4. The divisive classification procedure applied to four consecutive weekly Coleoptera samples over early summer, is suggested as a means of describing and identifying terrestrial arthropod communities characteristic of site and year of collection. This approach provides a potentially sensitive tool for monitoring terrestrial ecosystems.
Factors affecting the rate of attack by Cotesia rubecula (Hymenoptera: Braconidae)
Authors: NEALIS VINCENT G.
Published: March 2008

Abstract. 1. The relationship between responses of the insect parasitoidCotesia rubecula (Marshall) to kairomones produced by the feeding activities of its host,Pieris rapae (L.), and patterns of parasitism were investigated under field conditions.

2. Parasitoid adults aggregated in patches with the highest densities of host larvae but there was no commensurate increase in the rate of attack in these patches.

3. The rate of attack was not limited by the availability of eggs.

4. The rate of parasitoid attack was highest where feeding damage by the host was highest, irrespective of current host density.

5. The rate of parasitoid attack was further influenced by host age distribution. Late instar larvae were less susceptible to parasitism than were early instar larvae. The rate of attack on early instar larvae occupying the same plants as late instar larvae was reduced. This reduction in rate of attack was due to limitations on parasitoid search time imposed by the increased feeding damage associated with large host larvae and by the increased time the parasitoid required to recover from an attack on these large host larvae.
Avoidance mechanisms of three Pieris butterfly species against the parasitoid wasp Apanteles glomerulus
Authors: OHSAKI NAOTA , SATO YOSHIBUMI
Published: March 2008

Abstract. 1. Experimental studies have shown that larvae of threePieris butterflies, P.rapae L., P.melete Mènètriés and P.napi L., are attacked by a parasitoid wasp, Apanteles glomeratus L. Although P.rapae larvae are parasitized heavily in the field, P.melete and P.napi are infrequently parasitized successfully because they possess mechanisms for encapsulating parasitoid larvae and for avoiding parasitism.

2. This study examines spatial and temporal variation in rates of parasitism of the three Pieris species by A.glomeratus in the field. We attempted to determine whether P.rapae possesses any means of avoiding parasitism by this wasp, and then to deduce why both P.melete and P.napi have more distinctive avoidance mechanisms than P.rapae.

3. Our results indicate that in temporary habitats, which are the main habitats of P.rapae, P.rapae is able to escape A.glomeratus in time and space by colonizing new habitats before the parasitoid arrives. In permanent habitats, however, such escape is not possible. P.rapae larvae lack physiological or behavioural avoidance mechanisms of reducing parasitism rates in permanent habitats. P.melete and P.napi, in contrast, live only in permanent habitats, where the parasitic pressure is potentially high, and have evolved active avoidance mechanisms.
The effects of temperature and prey density on the development rates and growth of damselfly larvae (Odonata: Zygoptera)
Authors: PICKUP JONATHAN , THOMPSON DAVID J.
Published: March 2008

Abstract. 1. The effects of prey density and temperature on the feeding and development rates of several late instars of the larvae of three common European damselflies (Lestes sponsa (Hansemann), Coenagrion puella (L.) and Ischnura elegans van der Linden) were investigated in a laboratory experiment.

2. Functional responses were used to estimate maximum feeding rates. Maximum feeding rates were compared between species, instars and temperatures by expressing prey consumption in terms of prey biomass consumed per unit predator biomass. Lestes was capable of feeding at almost twice the rate of either Coenagrion or Ischnura.

3. Higher feeding rates led to faster development rates and there was an interaction between species and temperature. With the exception of those with very low feeding rates, larvae maintained at higher temperatures, but similar feeding rates, developed faster. Under similar conditions of temperature and feeding rate, Lestes larvae developed faster than larvae of either Coenagrion or Ischnura.

4. Faster development rates at similar rates of food intake were achieved at the cost of reduced size‐increases between instars.

5. The differences in the responses of the three species are discussed in the light of their respective life histories, and with reference to a recent model of population regulation in damselflies.
Within‐plant distribution of a galling adelgid (Homoptera: Adelgidae): the consequences of conflicting survivorship, growth, and reproduction
Authors: FAY PHILIP A. , WHITHAM THOMAS G.
Published: March 2008

Abstract. 1. Adelges cooleyi (Gil.) was rarely found in the top‐most whorl of shoots in its host plant Engelmann spruce.

2. The survivorship of the few Adelges fundatrices which did colonize the top whorl was at or near zero for the 3 years in which survivorship was assessed, while survivorship in the bottom whorls was at least 60%.

3. In contrast, when an Adelges fundatrix did survive in the top whorl, her growth and reproductive output, and the growth of her progeny, the gallicolae, were at least double that of bottom whorl fundatrices.

4. The distribution of fundatrices within spruce trees was strongly correlated (R2=0.934) with fundatrix fitness (=survivorship × fecundity × growth).

5. We hypothesize that the vigorous growth of top whorl shoots promotes Adelges growth and fecundity, but the earlier growth of these shoots results in low temperature mortality of fundatrices.
Digestion rate in relation to alternative feeding in three species of polyphagous predators
Authors: LÖVEI GÁBOR L. , SOPP PAUL I. , SUNDERLAND KEITH D.
Published: March 2008

Abstract. 1. Disappearance of different amounts of aphid ingested by three species of polyphagous predators, the carabids Bembidion lampros (Herbst) and Nebria brevicollis (F.) and the staphylinid Philonthus cognatus Stephens, was monitored by a quantitative enzyme‐linked immunosorbent assay (ELISA). The effect on the rate of inactivation of prey antigens by the ingestion of subsequent, non‐aphid food was also studied.

2. Antigen inactivation was significantly more rapid in the staphyilinid than in the carabids.

3. No statistically significant differences were found in the rate of antigen inactivation between beetles which consumed only aphids and those which were given a different type of food after feeding on aphids; the detection period was longer in the former groups. A higher proportion of beetles with low levels of aphid antigen were found earlier in the latter group.

4. The results did not unequivocally support the prediction derived from optimal digestion theory that beetles without continuous access to food would retain an initial meal longer than beetles with unlimited access.
A functional classification for analysis of the structure of dung beetle assemblages
Authors: DOUBE BERNARD M.
Published: March 2008

Abstract. 1. Regional scarabaeid dung beetle assemblages in southern Africa may contain over 100 species, ranging in live weight from 10 mg to 10 g. These show a wide variety of dung‐use and reproductive strategies.

2. To facilitate analysis of these diverse assemblages, a system of classification analogous to guilds is proposed. Scarabaeid dung beetle species are allocated to one of seven functional groups (FGs) according to the way they use and disrupt dung. Each group therefore contains a set of species which are functional analogues of each other. This classification provides a conceptual framework within which to analyse the structure of dung beetle assemblages and the interactions between dung beetles and other dung‐breeding species such as coprophagous flies.

3. There is a clear hierarchy of functional groups in their ability to compete for dung. Competitively dominant groups such as the large ball rollers (FG I) and fast‐burying tunnellers (FG III) are mostly large, aggressive beetles which rapidly remove dung from the pad. The smaller ball rollers (FG II) are also effective competitors for dung. Subordinate groups are those which bury dung slowly over many days (FG IV and V) and those which breed inside the pad (FG VII, endocoprids). Kleptocoprids (FG VI) breed in dung buried by other beetles and so are not part of the hierarchy.

4. The use of this classification is illustrated by reference to three contrasting assemblages of dung beetles in a summer rainfall region of southern Africa. The potential of these beetles for biological control of dung‐breeding flies is discussed.
Insect responses to plant water deficits. II. Effect of water deficits in soybean plants on the growth and survival of Mexican bean beetle larvae
Authors: McQUATE GRANT. T. , CONNOR EDWARD F.
Published: March 2008

Abstract. 1. We examined the effect of water deficits in soybean, Glycine max [L.] Merr., on the growth and survival of Mexican bean beetle larvae, Epilachna varivestis Mulsant (Coleoptera: Coccinellidae).

2. Larvae were reared under growth chamber, glasshouse, and field conditions on foliage from plants that were either well‐watered or subjected to water deficits.

3. Larval survival, growth rate and pupal weight were reduced, and development time was increased when larvae were reared on foliage from plants subjected to water deficits. These results are contrary to White's (1974) hypothesis that water deficits in plants cause increased growth and survival of herbivorous insects.

4. Changes in foliage chemistry caused by water deficits, possibly in the concentration of free amino acids, are the most likely causes of the observed effects on growth rate and development time. However, under glasshouse and field conditions, physical changes in foliage and/or the foliage's environment that accompany water deficits are also important.
Bruchid egg mortality on Acacia farnesiana caused by ants and abiotic factors
Authors: TRAVESET ANNA
Published: March 2008

Abstract. 1. This study investigated the effect of arboreal ants on the bruchid beetles that prey upon the seeds of Acacia farnesiana (L.) Willd., a common shrub in the savannas of Santa Rosa National Park, in northwestern Costa Rica.

2. Experiments demonstrated that ants removed an average of about 50% of unhatched bruchid eggs that had been laid on the pods of this leguminous plant. Ants also removed shells of hatched eggs.

3. In addition to the mortality caused by ant predation, about 30% of the eggs disappeared before hatching, presumably due to the combined effects of temperature and wind.

4. The orientation of the branch on which a pod was located did not affect the proportion of eggs lost from that pod.
Competition, resource partitioning and coexistence of an endoparasitoid Encarsia perniciosi and an ectoparasitoid Aphytis melinus of the California red scale
Authors: YU D. S. , LUCK R. F. , MURDOCH W. W.
Published: March 2008

Abstract. 1. Laboratory experiments and field studies were conducted to explain the coexistence of an endoparasitoid, Encarsia perniciosi Tower, and an ectoparasitoid, Aphytis melinus DeBach, both of which were introduced into California to control the California red scale, Aonidiella aurantii (Mask.).

2. Encarsia parasitized all scale stages but it preferred first and second instar scales. This is in contrast to Aphytis melinus, in which previous studies have shown that it parasitizes second and third instar females and second instar males but prefers third instar female scales. Encarsia developed most rapidly when it parasitized an early second instar and slowest when it parasitized the mature female scale. However, on early second instar scales it was about 80% as fecund as a wasp that emerged from a mature female scale.

3. Second instar scales parasitized by Encarsia were accepted by Aphytis as readily as unparasitized scales.

4. Encarsia did not distinguish between unparasitized hosts and those previously parasitized by Aphytis.

5. Encarsia always outcompeted by Aphytis when both species parasitize the same host.

6. Encarsia prefers scale on stems whereas Aphytis prefers those on leaves and fruits. This, too, may be a result of interspecific competition with Aphytis.

7. The partitioning of the scale resource by the two species explains why they coexist in coastal southern California but it does not explain why Encarsia disappeared from citrus groves in the inland valleys coincident with the introduction of Aphytis melinus into southern California.
Field manipulation of populations of individual staphylinid species in cereals and their impact on aphid populations
Authors: DENNIS PETER , WRATTEN STEPHEN D.
Published: March 2008

Abstract.

Four 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.

A novel field cage design was used to exclude all but the staphylinid species under investigation.

Predator effects were compared with total‐exclusion cages in which all predators and parasitoids were kept out.

During a high‐density phase of aphid population development only Philonthus cognutus (Stephens) significantly influenced aphid population numbers.

At low aphid densities, Tachyporus obtusus (L.), T.chrysomelinus (L.) and P.cognatus reduced aphid population levels.

The experiments showed that Tachyporus spp. can reduce the numbers of cereal aphids prior to the exponential phase of aphid population increase and that P.cognatus causes some reduction at both the stages of aphid population growth investigated.
Brood sex ratios of the solitary parasitoid wasp,Coccophagus atratus
Authors: DONALDSON J. S. , WALTER G. H.
Published: March 2008

Abstract.

Female 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.

When 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.

Behavioural observations show that females do not move away from patches of hosts until all their eggs are laid, regardless of the host type.

Brood 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).

Our 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 ratios.
Brood guarding in a bethylid wasp
Authors: HARDY IAN C. W. , BLACKBURN TIM M.
Published: March 2008

Abstract.

Atypical of the parasitoid Hymenoptera, female Goniozus nephantidis Muesebeck remain with offspring until they pupate. This behaviour will only have evolved if the consequent reduction in fecundity is outweighed by fitness returns.

G.nephantidis competes for hosts with conspecific and non‐conspecific parasitoids. The effectiveness of G.nephantidis at deterring superparasitism and multiparasitism is tested. Brood survivorships were compared when G.nephantidis and Bracon hebetor Say intrude on hosts with the mother present and absent and with offspring at different developmental stages.

Laying 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.

Competitive asymmetries determined the outcome of contests for possession of host resources.

The costs of remaining seem at least partially offset by the prevention of oviposition by competing parasitoids.
Parasitization by Edovum puttleri (Hymenoptera: Eulophidae) in relation to host density in the field
Authors: RUBERSON JOHN R. , TAUBER MAURICE J. , TAUBER CATHERINE A. , GOLLANDS BRIAN
Published: March 2008

Abstract.

The relationship between parasitization by Edovum puttleri Grissell and density of eggs of the Colorado potato beetle, Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae), was studied on two spatial scales (eggs mass and 6 m2 cage).

For 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.

The 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.

Although overall levels of parasitism were relatively low, total mortality of L.decemlineata eggs (including nonviable and cannibalized eggs, and those killed by parasitoid feeding) in parasitized egg masses was consistently high (˜70–90%).
Estimating death rates from transect counts
Authors: ZONNEVELD COR
Published: March 2008

Abstract.

The time course of abundance of adult insects emerging in discrete generations is modelled, assuming the absence of net migration and a constant death rate. The time till emergence is assumed to be logistically distributed.

The qualitative features of the model depend on one dimensionless parameter only, namely the product of the death rate and a dispersion measure for the symmetric emergence distribution.

The model is fitted to data on the abundance of five butterfly species. The tit is excellent; moreover, the estimated death rates are well within the range given in the literature (mostly 0.1–0.2 day‐1). Death rates are generally obtained by mark‐recapture methods. The present model gives the opportunity to evaluate some assumptions of these methods.
Mechanisms of interference competition in the western tree‐hole mosquito, Aedes sierrensis
Authors: BROADIE KENDAL S. , BRADSHAW WILLIAM E.
Published: March 2008

Abstract.

Mechanisms of interference competition affecting Aedes sierrensis (Ludlow) were investigated in laboratory microcosms using reconstituted, natural tree‐hole detritus as food and substrate.

Pupation success, larval development time, and pupal weight were all affected by larval density but not by surface area:volume ratio of the microcosm.

Mature fourth instars affected pupation success, pupal weight, and development time of developing cohorts separated from them by a 2 μm pore membrane impermeable to bacteria, indicating that chemical competition is proportional to density of at least older instars.

Cannibalism does not occur, regardless of the presence or absence of food or physical complexity.

Fourth instars inhibited each other's feeding at densities of 64 larvae/ml or greater. Feeding inhibition due to physical contact (encounter competition) was abated but not eliminated by increasing physical complexity of the microcosm by the addition of leaves.

Levels of detritus and larval density both affect weight of day‐1 fourth instars. Resistance to encounter competition is proportional to fourth instar weight and weight‐specific resistance is correlated with rank weight within a developing cohort.

At densities around the population equilibrium in nature, encounter competition should be taking place, especially in tree holes with few leaves or other large litter.
Seasonal variation in generation time, diapause and cold hardiness in a central Ohio population of the flesh fly, Sarcophaga bullata
Authors: CHEN CHENG‐PING , DENLINGER DAVID L. , LEE RICHARD E.
Published: March 2008

Abstract.

Generation time, diapause phenology and cold tolerance of the flesh fly, Sarcophaga bullata, were examined under confined natural conditions in central Ohio. In this locality, the fly can complete a maximum of four generations annually.

Very few pupae entered diapause in the first and second generations (May to July in 1988). In the third generation (August) 37% of the pupae entered an overwintering diapause, as did all pupae from the fourth generation (September).

The adult eclosion date in the spring and annual generation time can be predicted accurately from degree day data.

Cold tolerance of the field‐overwintering portion of the population was high. After 30 days under field conditions, diapausing pupae readily survived a 7‐day exposure to — 17°C. Glycerol appears to be the major cryoprotectant in S.bullata, and glycerol concentrations in the field population (95–142 mm) remained high throughout the winter.

In contrast, diapausing flies reared under laboratory conditions (20°C, 12:12 LD) were less cold tolerant, and glycerol concentrations were lower (6.9–21.2 mm). Field conditions thus promote the acquisition of high levels of cold tolerance, presumably as a consequence of the accumulation of higher concentrations of glycerol.

In spite of differences in the cold tolerance of laboratory and field flies, the supercooling points of the two groups of flies were nearly the same, thus implying that the supercooling point is not a good indicator of cold tolerance.
Control of gall morphology: tephritid gallformers (Aciurina spp.) on rabbitbrush (Chrysothamnus)
Authors: DODSON GARY N.
Published: March 2008

Abstract.

Sibling species of tephritid flies occumng on separate subspecies of Chrysofhamizus nauseosus Hall and Clements have distinct gall moiphologies (smooth and cotton).

Cross matings of and subsequent confinement of the flies to particular host plants demonstrated that the insect's and not the plant's genotype dictated the morphology of the gall, although the plant genotype may determine whether or not a gall is produced.

The results implicate a possible single gene control mechanism for external gall morphology.
Intraspecific competition in larvae of the ant‐lion Morter sp. and interspecific interactions with Macroleon quinquemaculatus
Authors: GRIFFITHS DAVID
Published: March 2008

Abstract.

Intraspecific competition was investigated in the pit‐digging larvae of the ant‐lion Morter sp., which normally occurs at low density in a food‐rich habitat.

Morter larvae interact by displays, challenges, and sand tossing. Challenges/displays affected pit spacing while sand tossing affected pit size. Pit ownership determined the outcome of contests regardless of the relative sizes or feeding condition of the contestants.

Competition had no effect on the pit size of winners but losers showed a density dependent reduction in pit size. Interference competition caused a density dependent reduction in larval growth rates.

Macroleon quinquemaculatus (Hagen) always won contests with Morter, even when smaller. Cannibalism occurred in 60% of these contests.

Little intraspecific competition occurs in Morter in the field. Morter is more willing to incur energy costs than Macroleon.
Response of fire ants (Formicidae: Solenopsis invicta and S.gerninata) to artificial nectars with amino acids
Authors: LANZA JANET
Published: March 2008

Abstract.

The role that amino acids in extrafloral nectars play in attracting ants to plants was investigated. Workers from laboratory colonies of Solenopsis invicta Buren and S.geminafa (F). (Formicidae) fed from artificial nectaries containing mimics of the extrafloral nectar of Passiflora menispermifoh and P.caerulea; P.menispermifoh nectar contains higher levels of amino acids (1347.3 pdml) than does the nectar of P.currulea (125.2 μm/ml).

When sugar‐only and sugar—amino acid nectar mimics were presented simultaneously, more S.invicta workers were counted at sugar—amino acid nectar mimics than at sugar‐only nectars. S.geminatu did not discriminate between the two nectars.

When the two Pamiflora L. nectar mimics were presented simultaneously, S.invicta and S.geminata workers were more abundant at the nectaries containing high levels of amino acids (P.menispermifolia HBK mimic) than at the nectaries containing low levels of amino acids (P.cuerulea L. mimic).

The behaviour shown by S.invicta and S.gerninata suggests that plants with high levels of amino acids in their extrafloral nectars attract more ant protectors and might suffer less herbivory than plants producing nectars with low levels of amino acids. If so, ants may favour, over evolutionary time, plants that produce nectars with high levels of amino acids.

Day‐to‐day variability in ant behaviour was considerable even among laboratory colonies maintained on the same diet in similar environmental conditions. This variability will reduce the selective impact that ants have on plants and may help to explain why most ant‐plant interactions are facultative.
Is host‐plant quality responsible for the populational pulses of salt‐marsh planthoppers (Homoptera: Delphacidae) in northwestern Florida?
Authors: SILVANIMA JAMES V. C. , STRONG DONALD R.
Published: March 2008

Abstract.

Rare populational pulses of the sibling species of plant‐hoppers Prokelisia dolus Wilson and P.marginata (Van Duzee) occur along the Gulf Coast of Florida. Densities at least three standard deviations ahove the average number of adult planthoppers per stem host plant are exhibited during these pulses.

This context of rare local irruptions provides a basis for testing a component of T. C. R. White's hypothesis, which states that the trigger for insect outbreaks is an increase in the nutritional quality, in terms of available nitrogen, of host‐plant tissue.

In the field, over approximately five generations of these hoppers (9 months), we elevated foliar nitrogen in host plants substantially by fertilizing, six times, salt‐marsh plots of 10 m2 with ammonium nitrate. No densities approaching a populational pulse occurred in either fertilized or unfertilized plots during the course of this study or in the year following. Fertilization did increase adult densities in the spring but this increase deteriorated over the summer months and was lost in the autumn. Host plants in fertilized plots retained high levels of nitrogen for at least the second year.

Several very dense pulses, of more than thirty adult hoppers per stem, occurred at other sites during the course of this study. Host‐plant nitrogen in a pulse site did not differ from that found in host plants immediately adjacent to the pulse. We conclude that increased foliar nitrogen is not the proximate cause of the populational pulse behaviour exhibited by these planthoppers.

We speculate that these pulses result from behavioural aggregation of adult hoppers.
Sex ratios in field populations of Epidinocarsis lopezi, an exotic parasitoid of the cassava mealybug, in Africa
Authors: DIJKEN MARIANNE J. VAN , NEUENSCHWANDER PETER , ALPHEN JACQUES J. M. VAN , HAMMOND WINFRED N. O.
Published: March 2008

Abstract.

In cassava fields in Africa, population sex ratios of Epidinocarsis fopezi vaned from 0.44 (males to total parasitoids) at low host densities to highly male‐biased ratios of 0.70 at high host densities.

This variability is caused by the difference in allocation of sons and daughters to hosts of different sizes, through the following mechanisms: (a) small, i.e. second instar, hosts are mainly used for the production of male offspring, whereas in large, i.e. third instar, hosts a variable, female‐biased sex ratio is produced; (b) E.fopezi does not selectively oviposit into large hosts but always accepts both small and large hosts for oviposition upon encountering; (c) in the field, this parasitoid is time‐limited, and not egg‐limited. On the basis of an optimal diet model, such general host acceptance is shown to be the best strategy.

Thus, sex ratio increases with host density for three reasons: the proportion of small hosts encountered in the field increases with increasing host density, small hosts are used for male production, and hosts are always accepted when encountered.
Ecology of baculovirus‐infected and healthy adults of Oryctes rhinoceros (Coleoptera: Scarabaeidae) on coconut palms in the Philippines
Authors: ZELAZNY B. , ALFILER A. R.
Published: March 2008

Abstract.

Males and females of Oryctes rhinoceros (L.), a serious pest of coconut palms, congregate in decaying coconut trunks to mate, oviposit and prepare the wood for the young larvae. A baculovirus disease is often transmitted from beetle to beetle in this environment and transmission to and from larvae probably also occurs.

Young beetles are mainly found feeding on palms, where they also frequently contract the virus disease, presumably through mating with diseased partners.

Monitoring beetle populations in the Philippines with attractant traps and by collections from palms showed seasonal fluctuations which were often inversely correlated with the incidence of the virus disease. Disease prevalence matched closely the proportion of females in the population. Possible explanations for this correlation and for the seasonality of the disease prevalence are outlined.
The seasonality of arboreal arthropods foraging within an Australian rainforest tree
Authors: BASSET YVES
Published: March 2008

Abstract.

The seasonality of arboreal arthropods foraging within the crown of the canopy tree Argyrodendron actinophyllum. Edlin (Sterculiaceae) was studied in a subtropical rain forest near Brisbane, Australia, during 2 years with interception traps and restricted canopy fogging.

Minimal air temperatures explained most of the seasonal variance in arthropod‘density activity'. However, the host phenology was important for several phytophagous groups. Rainfall, relative humidity and lunar phase influenced arthropod activity slightly.

Seasonal ranges were significantly different among arboreal guilds and were related to food resource availability in time, associated with both the host and the rainforest environment. Seasonal peaks of herbivores were more marked than in tropical rain forests, but less sharp than in temperate woodlands.'

Quantitative changes in arthropod density activity and abundance were important for most groups, with a marked trough during cool and dry months. The numerical contribution of most arthropod guilds to the arboreal community was not constant throughout the year.

Seasonal changes in the species composition of the arboreal community appeared not as a succession of well‐defined subcommunities throughout the year, but as a continuum of species of extended seasonal ranges.

This subtropical insect‐plant system presented several phenological features which were classified under tropical and temperate characteristics. This partition is open to discussion.
The influence of the ability to disperse on generation length and population size in the flour beetle, Tribolium castaneum
Authors: BEN‐SHLOMO RACHEL , MOTRO UZI , RITTE UZI
Published: March 2008

Abstract.

In Tribolium castaneum Herbst, in which dispersal is genetically determined, it is possible to select for strains that are characterized by high and low dispersal, High dispersal (HD) beetles are better adapted than low dispersal (LD) beetles for colonization, as can be seen from differences that exist between the two groups with regard to several life‐history parameters.

Comparisons were made between the dynamics of seventy‐two HD and seventy‐two LD populations. Generation length in HD populations was significantly shorter than in LD populations. After 91/2 weeks, in open treatments (from which dispersal away from the set was allowed), HD populations had more beetles than LD populations, whereas in closed treatments (from which dispersal away from the set was not allowed) the opposite was true.

These findings may explain the maintenance of the genetic variability of dispersal behaviour in natural populations of T.castmeurn.
Pine sawfly defence and variation in host plant resin acids: a trade‐off with growth
Authors: BJÖRKMAN CHRISTER , LARSSON STIG
Published: March 2008

Abstract.

The defence capability of pine sawfly larvae reared on Scots pines with low or high concentrations of resin acids was determined in a field experiment, where larvae were exposed to predatory ants, and in a laboratory experiment in which the rate of defence droplet replenishment was measured.

Larvae on low resin‐acid shoots disappeared faster than larvae on high resin‐acid shoots when exposed to predatory ants.

Larvae fed high resin‐acid needles produced 50% larger defence droplets than larvae fed low resin‐acid needles.

In an additional experiment high predation pressure was simulated by repeatedly removing defence droplets. Larvae responded by feeding more on tissue rich in resin acids, but at the cost of a reduction in growth rate.

Based on these data and earlier findings that survival and development of sawfly larvae are negatively affected by high resin‐acid concentrations, we conclude that pine sawflies face a dilemma of conflicting demands, i.e. although high needle resin‐acid concentrations enhance defence capability, they also reduce growth and survival. Our data also suggest that it is not necessarily the ovipositing female that has to balance this trade‐off: plasticity in larval feeding behaviour provides larvae with a means to at least partly solve the dilemma.
Phenotypic plasticity, seasonal climate and the population biology of Bicyclus butterflies (Satyridae) in Malawi
Authors: BRAKEFIELD PAUL M. , REITSMA NICO
Published: March 2008

Abstract.

Seasonal polyphenism is studied in a community of five African butterflies of the genus Bicyclus at the transition between a wet and a dry season from May to July.

Butterflies characterized by large eyespots and, especially in B.sufitza (Hewitson), a pale band (the wet season form) are replaced over this period by butterflies lacking conspicuous wing markings (the dry season form, dsf). The latter butterflies also tend to be larger, but more variable in size. Butterflies of an intermediate phenotype are recruited over a comparatively short interim period.

This turnover coincides with a period of declining temperature and drying of the habitat, including the grasses on which larvae feed. Butterflies are progressively more likely to rest on brown leaf litter rather than on green herbage.

A relationship with temperature is supported by laboratory experiments with B.saJitza and B.anynana (Butler) showing that increasingly extreme dsf butterflies develop with decreasing rearing temperature in the final larval instar.

Some differences in behaviour and activity were observed between the seasonal forms. Butterflies of the dsf develop ovarian dormancy and fat bodies. They can survive to reproduce at the beginning of the rains in November.

Capture‐recapture experiments showed that the adult butterflies have a comparatively long life expectancy and are quite sedentary.

The results are discussed in relation to a hypothesis linking the polyphenism to seasonal changes in resting background and selection for crypsis.