bluuebunny/crossref_metadata_2025_split huggingface dataset:
Variance in number of eggs per patch: oviposition behaviour and population dispersion in a seed parasitic moth
Authors: THOMPSON JOHN N. 
Published: March 2008

ABSTRACT. 1. The relationship between oviposition behaviour and population dispersion was analysed for Grey a subalba Braun (Lep., Incurvariidae), a species in which females usually, but not invariably. lay eggs in only a few schizocarps (seed‐pairs) on each umbellet they visit on Lomatium dissectum (Umbelliferae). During each of four years females exhibited a constant probability of leaving an umbellet after each egg was laid. Hence, some umbellets received more eggs than others and the behaviour matched a geometric distribution of eggs among umbellets.2. The variance in number of schizocarps attacked per umbellet by individual females did not result from females choosing schizocarps of particular sizes or avoiding schizocarps that already contained eggs or larvae. A potential, but speculative, explanation of the variance is that females distribute their eggs among umbellets in a way that maximizes unpredictability on larval dispersion to a searching parasitoid, The pattern of oviposition by Greya females fits the truncated geometric distribution that is predicted if information, as indexed by the Shannon‐Wiener entropy measure, is minimized. None the less, other measures of unpredictability or minimum information are possible, and the results highlight the problem of how to identify patterns of movement that may result from selection for unpredictability to enemies.3. In systematic surveys of the L.dissectum population during three consecutive years, virtually all plants had between 10% and 65% of their seeds attacked. Hence, the separation of oviposition bouts between umbellets and the constant probability of leaving an umbellet after each egg was laid resulted in a broad distribution of Greya attack among L.dissectum plants.
Population density, phenotype and reproductive output in the grasshopper Chorthippus brunneus
Authors: WALL RICHARD , BEGON MICHAEL 
Published: March 2008

ABSTRACT. 1. The effects of population density on the reproductive output of individual female grasshoppers (Chorthippus brunneus Thunberg) and the relationships between reproductive output and component elements of each female's phenotype, were investigated.2. Reproductive output was primarily determined by the rate of egg‐pod production. Increased density led to significant reductions in the rate of egg‐pod production and reproductive output.3. Exoskeleton size (reflecting nymphal experience) was positively correlated with clutch size at both high and low densities, but condition (reflecting adult experience) showed no such correlation. At high density, exoskeleton size was more strongly correlated with the rate of egg‐pod production and reproductive output than condition. It is concluded that the nymphal aspects of size are more important than the adult aspects.4. At low density, females with small exoskeletons compensated for their smaller clutches by producing egg‐pods at a faster rate. Thus, there was no overall relationship between reproductive output and any of the phenotypic characteristics.5. The effects of competition were weakly asymmetric in high density populations. The weakness of the asymmetry suggests scramble‐like interactions for resources. It is concluded that not only are the effects of competition influenced by individual differences, but also that competition may reveal differences that would not otherwise be apparent.
Seasonal and individual variation in gregarine parasite levels in the field crickets Gryllus veletis and G.pennsylvanicus
Authors: ZUK MARLENE 
Published: March 2008

ABSTRACT. 1. Gregarines, debilitating protozoan gut parasites, were monitored in two species of field cricket, Gryllus veletis (Alexander and Bigelow) and G.pennsylvanicus Burmeister, in northern Michigan in 1983 and 1984.2. Gregarines were found in 31–51% of G.veletis individuals and 50–70% of G.pennsylvanicus.3. Males were more heavily infected than females in G. veleris, but G.pennsylvanicus males and females had nearly equal infection levels; this disparity resulted in an overall lower infection rate for G. veletis.4. Both species had fewer gregarines in 1983 than in 1984, possibly due to the adverse effect of drier conditions in 1983 on development of parasite cysts in the soil.5. Levels of infection were not constant throughout the breeding season for either cricket species.6. Body size was not correlated with parasite load in either G. veletis or G.pennsylvanicus.7. Adult age was unrelated to gregarine level in G. veferis, whereas G.pennsylvanicus showed a positive correlation between adult age and parasite load during two non‐consecutive weeks of the breeding season.
Role of host‐plant stimuli in sexual behaviour of small ermine moths (Yponomeuta)
Authors: HENDRIKSE ANS , VOS‐BÜNNEMEYER ELLY 
Published: March 2008

ABSTRACT. 1. Studies involving experiments with olfactometers and field experiments have shown that the release of sex‐pheromone by females of Yponomeuta spp. is stimulated by the presence of host plants.2. While in Y.evonymellus L. less females emitted pheromone in the absence of host plants, in Y.padellus L. the initiation of pheromone release was delayed.3. Females of Y.evonymellus, Y.cagnagellus Hüb., Y.padellus and Y.plumbellus D. & S. all preferred a place with host‐plant odour to one with non‐host odours for sex‐pheromone release.4. Male preference for host‐plant odour was demonstrated in the laboratory only for Y.cagnagellus.5. Trap catches in the field indicated a reinforcement of female attractiveness by host‐plant stimuli.
A comparative study of the relationship between host size and brood size in Apanteles spp. (Hymenoptera: Braconidae)
Authors: Le MASURIER A. D. 
Published: March 2008

ABSTRACT. 1. Current models of insect oviposition predict that clutch size in parasitoids should correlate with host size, with a continuum from solitary species at one end to large gregarious broods at the other. This prediction is tested for the genus Apanteles (sensu lato).2. The distribution of brood sizes in Apanteles is bimodal, with peaks at one (solitary species) and at about twenty (gregarious species).3. Brood size of gregarious species correlates with host size, but when a measure of the total volume of a parasitoid brood is plotted against host size, solitary species do not lie on the same regression slope as gregarious species.4. There is a relative shortage of gregarious species on small hosts, and a relative excess of solitary species on large hosts. Solitary species on large hosts do not fully consume the host resource.5. The possible role of evolutionary constraints to adaptive progeny allocation in Apanteles is discussed.
Egg hatching inhibition: field evidence for population regulation in a treehole mosquito
Authors: LIVDAHL TODD P. , EDGERLY JANICE S. 
Published: March 2008

ABSTRACT. 1. We investigated the influence of larval density on egg hatching in the treehole mosquito, Aedes triseriatus Say (Diptera: Culicidae) by submerging laboratory‐produced egg batches in natural habitats stocked with fixed densities of larvae.2. We found a significant decrease in hatching rate as larval density increased. The results suggest that inhibited eggs refrain from hatching into environments in which competitive effects of large larvae are potentially severe, and in which cannibalism may occur.3. The amount of time the egg batches were exposed to experimental conditions (between 2 and 16 days) had no significant influence on hatch rate.
Activity budgets, habitat use and body size in two coexisting species of sand wasps (Microbembex: Sphecidae, Hymenoptera)
Authors: TOFT CATHERINE A. 
Published: March 2008

ABSTRACT. 1. Two superficially similar species of Microbembex, M.monodonta (Say) and M.cubana Bohart (Hymenoptera, Sphecidae, Nyssoninae), occur syntopically on Staniel Cay, a small Bahamian island (15 km2).2. Nesting (female) and territorial (male) aggregations of M.cubana were smaller and more numerous than those of M.monodonta in the study site and on the island as a whole.3. Both species had regular patterns of daily activities that required them to use a variety of microhabitats in the study area.4. Males of both species defended territories from c. 09.00 to 12.00 hours EST (in May) and the left to feed on nectar until they retired to sleeping burrows, typically from 13.00 to 15.00 hours. Male M.monodonta were active longer each day and intermixed feeding and territorial defence more than did male M.cubana.5. Females of both species were active for longer each day, from c. 08.30 to 15.30 hours, and intermixed their respective activities – hunting for provisions, feeding, and nest digging and maintenance – during each day more than did males. Female M.monodonta were active longer each day, rising earlier and retiring later, than female M.cubana.6. In M.monodonta, females were larger (length, X =11.00 mm) than males (10.5 mm). In M.cubana, males were larger (11.1 mm) than females (10.4 mm). Although mean differences were small, they were highly significant (F=22.42; P<10−4) for the species‐sex interaction.7. Differences in activity budgets, habitat use, and sexual size dimorphism appear to be related. A combination of factors, particularly thermal constraints, possible competition, and different mating systems, could explain these patterns.
Deme formation in scale insects: a test with the pinyon needle scale and a review of other evidence
Authors: UNRUH T. R. , LUCK R. F. 
Published: March 2008

ABSTRACT. 1. Deme formation is the transformation of a generalist population into one which is adapted to its local conditions. This adaptation has been inferred from many things but should be inferred from higher survival or fecundity of scale insects on their natal tree compared to that of immigrant scales on the same tree.2. Transfers of the scale insect Matsucoccus acalyptus Herbert within and between infested host trees (Pinus monophylla (Torr. & Frem.) resulted in significant differences in scale survivorship among recipient trees. Survival on individual trees was correlated across years, indicating stable differences in tree susceptibility to scale.3. A significant natal tree colonized tree interaction was observed for late stage scale survival in one experiment but the interaction was not caused by superior survivorship of scales transferred back to the natal tree. Hence, we found no evidence of deme formation in M.acalyptus.4. Previous studies have concluded that deme formation occurs in the black pineleaf scale based on a significant natal tree by colonized tree interaction in scale survival. We question this conclusion because the experimental design employed did not include transfers back onto the natal tree. Other indirect evidence for deme formation in scale insects is critically discussed.
Growth, reproduction and mortality in marine littoral Collembola at different salinities
Authors: WITTEVEEN J. , JOOSSE E. N. G. 
Published: March 2008

ABSTRACT. 1. A comparative study was performed on growth, reproduction and mortality of three species of marine littoral Collembola: the grassland species, Isotoma viridis (Bourlet), the littoral Hypogastrura viatica (Tullberg) and the intertidal Anurida maritima (Guérin), at different salinities.2. I. viridis and H. viatica both occur in salt marshes that are only inundated by seawater at very high tides. The first species lives in the higher less saline area and the second in the lower area, where during summer brackish and even hypersaline conditions may occur. The intertidal A.maritima is mainly found at salinities similar to the local seawater.3. I.viridis and H.viatica both show maximal growth and reproduction and a very low mortality at low salinities, but the latter species is better adapted to higher salinities. A difference between A.maritima and the other two species is that A.maritima is unable to survive freshwater conditions; rather it has an ecological optimum at salinities similar to seawater.4. A salt‐marsh population of I.viridis showed a better survival and a slightly better growth at saline conditions than an inland population of this species.5. We suggest that H.viatica, living in a very unstable environment, can be considered as a typical r‐strategist, while A.maritima, living in a predictable habitat, is more a K‐strategist.
Why a gall former can be a good biocontrol agent: the gall wasp Trichilogaster acaciaelongifoliae and the weed Acacia longifolia
Authors: DENNILL G. B. 
Published: March 2008

ABSTRACT.

The pteromalid Trichilogaster acaciaelongifoliae (Froggatt) causes galls to develop in the place of inflorescences during the reproductive phase of its host Acacia longifolia (Andr.) Willd. (Fabaceae). After being introduced to South Africa during 1982 and 1983, this wasp reduced the reproductive potential of A. longifolia by >89% when only 50% of the branches on a tree were galled. In addition, vegetative growth of galled branches was reduced by 53% when the vacated galls had desiccated.
The wasp is able to manipulate its host so effectively because: (a) the dry mass of developing galls was significantly greater than that of the corresponding reproductive organs, peaking in spring (September) when galls were 25 times the mass of unfertilized inflorescences. (b) The large biomass diverted to gall production is accounted for by a high proportion (66–73%) of multiple‐chambered galls. The dry mass of multiple‐chambered galls was significantly greater than that of both single‐chambered galls and pods. (c) The extent of biomass diversion to gall production was relatively greater during the earlier part of the reproductive season, enhancing stress on the host. (d) The wasp sometimes forced the plant to produce up to 200% more galls per branch than the normal quota of inflorescences. This phenomenon, called forced commitment, further increases stress on the host plant. (e) Galls constituted up to 21% and 40% of the dry and wet biomass of above‐ground parts of infested trees, respectively. This caused breakage and mortality of large branches and stems. (f) Reproduction in A. longifolia has been shown elsewhere to be so energy consuming that vegetative growth is strongly inversely related to pod production. Because the stress from galling by T. acaciaelongifoliae coincides with and replaces reproduction with a greater stress, successful reduction of both reproduction and vegetative growth are achieved.
This biological control programme is the first in which a gall‐forming hymenopteran has been used to control a weed. Since the effects of gall‐formers are indirect compared with those of insects attacking vegetative plant parts, their potential as biocontrol agents has been underrated. This research provides ecologically based guidelines for the future selection of such agents.
Leaf age and larval performance of the leaf beetle Paropsis atomaria
Authors: LARSSON STIG , CSIRO CLIFFORD P. OHMART 
Published: March 2008

ABSTRACT.

Larval performance of the leaf beetle Paropsis atomaria Oliver was determined for larvae raised on both new and mature leaves of Eucalyptus blakelyi Maiden. Larvae were transferred to mature leaves at different ages; control larvae stayed on new leaves through all instars.
Only larvae reared on new leaves through the third instar survived to pupate on mature leaves; developmental time was prolonged by 20% and pupal weight was reduced by 50% in these larvae compared with larvae reared entirely on new leaves. Almost all larvae died when transferred to mature leaves as first, second or third instars.
Low survival and slow development on mature leaves was mainly due to failure by larvae to feed. Larvae palpated leaves and could discriminate among leaf ages immediately, without biting into the leaf tissue.
New leaves had higher concentrations of oil and tannins than old leaves, while there were no significant differences in nitrogen concentrations in the two types of leaves. Mature leaves were more than 3 times tougher than new leaves, in terms of g mm−2 of penetrometer force.
In drought years E. blakelyi may not produce sufficient new leaves to supply specialist herbivores with their preferred food resource. We infer that drought years reduce P. atomaria larval performance significantly, and influence the population dynamics of the insect.
Genetical and ecological differentiation across a hybrid zone
Authors: NICHOLS RICHARD A. , HEWITT GODFREY M. 
Published: March 2008

ABSTRACT.

There is a narrow hybrid zone between two chromosomal races of the grasshopper Podisma pedestris (L.) in the French Alps.
There are no gross differences in habitat across the zone, and a multivariate analysis of the vegetation composition detected no significant transition either.
The hatch and development rates of Podisma in hybrid populations were lower than those found in matched habitat types outside the zone.
The simplest explanation for the persistence of the parapatric distribution of the two races is that hybrid disadvantage is maintaining a tension zone between them.
Effects of predation on clutch size and egg dispersion in the codling moth Laspeyresia pomonella
Authors: SUBINPRASERT SUTAT , SVENSSON BO W. 
Published: March 2008

ABSTRACT.

The effects of predation on clutch size and egg dispersion in the codling moth Laspeyresia pomonella (L.) were experimentally studied in an orchard by recording survival of eggs glued onto different substrates.
Egg mortality due to sucking insects was readily distinguishable from that due to chewing insects.
In both the field and laboratory, females preferred to deposit eggs singly on the uppersides of leaves.
Eggs on the uppersides of leaves and on fruit survived significantly better than did those on the undersides of leaves or on twigs.
Egg losses were highest during the early part of the flight season.
The smallest (one egg) and largest (nine eggs) clutches, associated with one egg‐bearing leaf per twig, both suffered the lowest rates of predation. Factors selecting against oviposition on fruits and production of large clutch sizes are presented and discussed.
Activity patterns and egg production in Coccophagus bartletti, an aphelinid parasitoid of scale insects
Authors: WALTER G. H. 
Published: March 2008

ABSTRACT.

Daily patterns of oviposition and host‐feeding were examined in Coccophagus bartletti Annecke & Insley. Females began to host‐feed and oviposit during the second or third day after emergence. Thereafter, both activities occurred regularly.
During long observation periods (5 h) most oviposition (93%) and host‐feeding (90%) occurred within the first 3.5 h of wasps first encountering hosts. Experiments demonstrated that levels of activity were low for the rest of the day, and nocturnal oviposition occurred only if wasps had no alternative.
Dissection of female wasps that had been exposed to hosts, or withheld from them, for given periods of time, revealed that activity levels are governed by egg availability. Dispersal activity may also be influenced by the physiological state of the ovaries.
Production of a full complement of eggs (at 24±1°C (12 h L) and 18±1°C (12 h D)) took 48h or longer after host‐feeding, and if wasps were withheld from hosts and provided with honey, the effects of egg resorption could be detected after about 10 days. Trends in oögenesis and oösorption in C. bartletti females seem not to conform with interpretations of oögenesis‐oösorption cycles in other parasitoids.
The pattern of activity exhibited by C. bartletti females is not inflexible, but the major aspects mentioned above are species‐specific. In general, information is needed about daily and hourly patterns of parasitoid oviposition and host‐feeding before experiments are designed to test theories of parasitoid behaviour. Interpretation may otherwise rest on assumptions about their physiological condition.
Egg laying decisions by the bean weevil Callosobruchus maculatus
Authors: WILSON KENNETH 
Published: March 2008

ABSTRACT.

Previous work has shown that female Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) can accurately assess the number of eggs on a seed and use this information to produce a near uniform distribution of egg‐loads, so minimizing larval competition within hosts.
The decision to lay on a particular seed may be based on one of two possible rules: (i) a‘relative’rule, which compares the number of eggs on the present seed with that on previously encountered seeds; and (ii) an‘absolute’rule, which takes into account the current egg‐load alone.
This paper describes an experimental study of oviposition behaviour which concludes that an absolute measure of egg‐load probably determines egg‐laying decisions. The implications of this result are discussed.
Foraging rate of ants collecting honeydew or extrafloral nectar, and some possible constraints
Authors: DREISIG HANS 
Published: March 2008

ABSTRACT.

In a given ant species, the number of ants collecting honeydew in an aphid colony or extrafloral nectar on a plant is proportional to the productivity of the colony or plant. Thus, the number of ants per resource unit and the ingestion rate per ant are constant for a species.
Mean number of ants per resource unit and ingestion rate per ant differed considerably between the investigated species. The ingestion rate increases with the body size of the species and decreases with an increase of the mean number of ants per resource unit.
Ingestion rates were higher in ants foraging singly at the resource than in ants foraging in the normal way in a group.
It is suggested that the ingestion rate per ant is reduced below a maximum level by the number of ants present per resource unit because a certain number of ants is needed to defend the resource against alien ants. Small species need more individuals for this purpose than large species, and consequently suffer a larger reduction of their ingestion rate.
Determinants of foraging profitability in two nectarivorous butterflies
Authors: MAY PETER G. 
Published: March 2008

ABSTRACT.

I studied flower selection and foraging energetics of Agraulis vanillae L. (Nymphalidae) and Phoebis sennae (Pieridae), two butterfly species common to north central Florida. I identified the major nectar resources exploited by several populations of these butterflies and, for each plant species, measured available nectar volumes and concentrations, corolla lengths, and density. I quantified foraging behaviour of each butterfly species at each nectar source (flower visitation rate and percentage of foraging time in flight), and used these data to estimate the net rate of energy intake of each butterfly species at each nectar source.
Estimated mean energy contents of individual flowers of the eleven exploited plant species spanned three orders of magnitude, ranging between 0.015 and 9.27 joules. Mean energy content of individual flowers was strongly correlated with mean foraging profit of both butterfly species.
Mean nectar volume strongly influenced energy content and varied widely within and among species, ranging from 0.0076 to 1.853 μ1. Nectar concentration varied between 17.1% and 40.4% sucrose‐equivalents. Nectar volume was the best single predictor of foraging profitability (correlation coefficients of 0.994 and 0.984 for Phoebis and Agraulis respectively). Corolla length also strongly affected foraging profitability for both butterfly species; flower species with longer corollas were generally more profitable.
Flower density and nectar concentration showed weak or nonsignificant associations with foraging profitability.
The usefulness and limitations of these floral characteristics as bases for foraging selectivity, and the selective pressures foraging butterflies might place on the visited plants are discussed.