bluuebunny/crossref_metadata_2025 huggingface dataset:
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.
Refugia and habitat partitioning among midges (Diptera: Chironomidae) in rain‐pools
Authors: McLACHLAN ATHOL J.
Published: March 2008

ABSTRACT.

Rain‐pools on granite exposures are common in tropical Africa and they are inhabited by the larvae of two midge species, Chironomus imicola Kieffer and Chironomus pulcher Wiedemann.

These pools differ from other ephemeral island habitats such as carrion, fallen fruit, sap flows, mushrooms and dung in their high degree of spatial predictability. Most pools are predictably inhabited by either C.imicola or C.pulcher. This finding is considered in the light of contemporary competition theory.

An arrangement whereby the same species repeatedly invades the same temporary habitat indicates that there is something about the habitat itself causing the discrimination. I suggest that degree of exposure to sunlight may provide a cue allowing females to discriminate between pools as oviposition sites.

Both species survive the long dry season by retreating to pools of river water left by receding rivers. Dispersal to rain‐pools by emerging adults occurs during the following season with imicola occupying rain‐pools remote from shaded rivers. Appropriately, measured against pulcher, the biology of imicola is that of a colonizing species.

The possibility is discussed that the chironomids in rock‐pools do not survive to breed. Instead, these populations may be maintained externally, for example by invasions from breeding populations in the Great Lakes of Africa, where larval densities may be too low to be detected by sampling. The evolutionary implications of such a situation are considered.
Are galling insects better protected against parasitoids than exposed feeders?: a test using tenthredinid sawflies
Authors: PRICE PETER W. , PSCHORN‐WALCHER H.
Published: March 2008

ABSTRACT.

Data mostly from the published literature were used to assess the effect of galling on the number of parasitoid species per host species in the phylogeny of nematine sawflies from free external feeders (colonial and solitary) to leaf gallers and shoot gallers.

The strongest effects of galling were the total elimination of the species‐rich cocoon‐attacking guild of parasitoids, and eonymphal parasitoids, from the parasitoid community on shoot gallers, all of which are in the genus Euura.

All tachinid larval parasitoids were also eliminated by the galling habit.

The cumulative effects of these exclusions resulted in a decline in mean number of parasitoid species per host species from almost sixteen species on external colonial feeders to 4.0 species on shoot gallers.

General patterns in per cent parasitism by non‐tachinid and tachinid larval parasitoids, eonymphal and cocoon parasitoids, on exposed feeders to shoot gallers, showed declines in non‐tachinid attack and elimination of tachinid, eonymphal and cocoon parasitoids. But leaf gallers tended to be attacked more than exposed feeders by non‐tachinid larval parasitoids.

The galling habit had a long‐term impact by reducing the number of parasitoid species attacking nematine sawfly gallers and per cent mortality inflicted, so that natural enemies may have been important as a selective factor in the evolution of galling nematine sawflies.
Spatial and temporal patterns of predation by ants on eggs of Cactoblastis cactorum
Authors: ROBERTSON HAMISH G.
Published: March 2008

ABSTRACT.

Predation of Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae) eggs by ants was studied for a summer and a winter generation on prickly pear Opuntia ficus‐indica (L.) Miller plants in the field.

Egg Predation between plants was spatially density‐dependent in the winter but not in the summer generation.

To test for the presence of delayed density‐dependent mortality within generations, percentage egg Predation during 5‐day periods was plotted against the number of eggs available in each period. Data points joined in a time sequence moved in an anticlockwise direction in the summer generation, suggesting a delayed density‐dependent response by the ants, whereas in the winter generation the points moved in a clockwise direction.

The degree of coincidence of the C. cactorum eggs with the peak larval production periods of the ants is suggested as the main reason for the temporal changes in egg Predation.
Interspecific competition between insect herbivores: asymmetric competition between cinnabar moth and the ragwort seed‐head fly
Authors: CRAWLEY M. J. , PATTRASUDHI R.
Published: March 2008

ABSTRACT.

Removal field experiments and observational studies have been undertaken to determine whether feeding by cinnabar moth Tyria jacobaeae L. on the flower heads of ragwort Senecio jacobaea L. affects the abundance of the fly Pegohylemyia seneciella (Meade) that feeds in the flower heads as a larva.

Correlations between the population density of cinnabar moth and the population density of the fly were suggestive of habitat separation, but provided little evidence of exploitation competition.

Removal of cinnabar moth by hand from replicated plots over two years shows that, in years when ragwort flower production is consumed by cinnabar moth caterpillars, the fly may show no recruitment at all.

Fly populations persist in refugia, exploiting ragwort plants that grow in areas where there are no cinnabar moth.

Recruitment of ragwort is not seed limited, so the reduction in seed production caused by P. seneciella (maximum about 30%) has no impact on ragwort abundance, or on the abundance of cinnabar moth.

We conclude that there is strong interspecific competition between these two species, and that the competition is highly asymmetric. The cinnabar moth had a substantial effect on the recruitment of the fly in 1986, but the fly has no measurable impact on the recruitment of the moth. In six years out of seven in our long‐term study, cinnabar moth reduced flower production to levels comparable to those measured in 1986, and we infer that strong competition with the fly was likely in six years out of seven.

One reason why there are so few published examples of asymmetric interspecific competition may be simply that the experiments are thought too obvious to be worth doing. We argue that this is not a good reason for eschewing manipulative field experiments, and that few processes in ecology are at all obvious when investigated in detail.
Adaptive significance of wing dimorphism in the absence of dispersal: a comparative study of wing morphs in the waterstrider, Gerris remigis
Authors: FAIRBAIRN DAPHNE J.
Published: March 2008

ABSTRACT.

Gerris remigis Say (Hemiptera; Gerridae) is primarily apterous, but populations with up to 33% macropters have been reported. The macropters seldom fly, and field studies have revealed no detectable differences between wing morphs in movement or survival at any time of year.

In this paper, life history traits of macropterous and apterous G. remigis are compared in an attempt to determine the mechanisms responsible for the maintenance of macroptery in this species in spite of the very low flight capacity and infrequent flight of macropters.

Development time, proportion breeding without diapause, and overwinter survival do not differ between morphs. However, pre‐diapause macropterous females have a significantly shorter pre‐oviposition period than apterous females. In contrast, post‐diapause macropters begin reproducing later than apters, and have a lower cumulative fecundity.

These results suggest that macropters may be at a selective advantage in warm habitats which favour pre‐diapause reproduction, but that apters should be favoured in the preferred, cool, lotic habitats.

However, crossing and rearing experiments indicate that wing morphology is primarily environmentally controlled in this species, and that the heritability of wing morphology is low, at best. In light of this, the relative impacts of purely phenotypic (environmental) variation, random effects, and the observed fitness differences on the maintenance of macroptery in this species are discussed.
Field experiments on a new method for determining age in tsetse flies (Diptera: Glossinidae)
Authors: LEHANE M. J. , HARGROVE J.
Published: March 2008

ABSTRACT.

Data are presented which suggests that the accurate determination of the age of tsetse flies (Glossina morsitans morsitans Westwood and G. pallidipes Austen) in the field can be achieved by measuring the fluorescence content of the head capsule.

The way in which this can be achieved and further work which would improve the accuracy of the technique are discussed.
Euphorine phylogeny: the evolution of diversity in host‐utilization by parasitoid wasps (Hymenoptera: Braconidae)
Authors: SHAW SCOTT RICHARD
Published: March 2008

ABSTRACT.

New data on the phylogeny of the braconid subfamily Euphorinae supports the hypothesis that parasitism of adult insects by Euphorinae originated during parasitism of Chrysomelidae, a group whose larvae are ecologically coincident with adults.

Evolution of the habit of attacking the adult stage opened a new adaptive zone; subsequently the Euphorinae have diversified on to a phylogenetically greater variety of hosts than any other braconid subfamily.

Parasitism of eumastacid grasshoppers evolved from beetle parasitism in the tribe Perilitini.

The tribe Euphorini shows the greatest diversity of hosts utilized. Most attack Heteroptera; however, Chrysopopthorus diversified on to adult Chrysopidae, Euphoriella on to Psocoptera, and Cryptoxilos on to Scolytidae.

Parasitism of bark beetles (Scolytidae) has evolved independently in three genera: Cosmophorus, Cryptoxilos and Ropalophorus. This is the most specialized form of beetle parasitism by euphorines, since it involves direct parasitism of concealed hosts.

Parasitism of adult hymenopterans by the tribe Syntretini may be related to attacking hosts while they are foraging at flowers.

The pattern of diversification in the Euphorinae indicates several adaptive radiations within host orders, as well as a history of major host‐shifts between phylogenetically distantly‐related host groups: Coleoptera to Orthoptera; Coleoptera to Hymenoptera; Coleoptera to Heteroptera; Heteroptera to Neuroptera, Psocoptera, and back to Coleoptera. Both the‘host taxonomy’and‘host habitat’hypotheses of host‐shifting are supported. Host‐shifts have involved hosts occurring in the same micro‐habitat and usually having similar feeding habits. This is consistent with current theory of host‐location by means of host‐produced kairomones and visual cues.
Habitat quality and reproductive investment in aphids
Authors: WALTERS K. F. A. , BROUGH C. , DIXON A. F. G.
Published: March 2008

ABSTRACT.

Genetically identical vetch aphids, Megoura viciae (Buckton), showed a weak but significant positive relationship between reproductive investment (number of ovarioles) and weight, here used as an indicator of habitat quality.

Apterae reared on poor quality plants showed the same range in numbers (twelve to twenty‐two) but on average fewer ovarioles than those reared on high quality plants.

The variability in ovariole number was determined prior to birth.

Under constant conditions the age of a mother does not affect the range of ovariole numbers or the proportion of her offspring in each ovariole class.

Apterae reared on poor quality host plants gave birth to proportionately fewer offspring with a high ovariole number than apterae reared on high quality plants.

Winged individuals gave birth to proportionately more offspring with a high number of ovarioles than apterae.

The control and ecological significance of the intramorph variation in reproductive tactics shown by many species of aphids is discussed in the light of these results.
The distribution of risk and density‐dependent mortality in the galls of Eurosta solidaginis, the goldenrod gall fly
Authors: WALTON ROD
Published: March 2008

ABSTRACT.

This paper explores the net effect of a suite of mortality factors on a sedentary prey, the larvae of the goldenrod gall fly, Eurosta solidaginis Fitch (Diptera: Tephritidae).

Mortality is caused by unknown factors early in larval development, two species of parasitoid wasp (Hymenoptera: Eurytomidae), an inquiline beetle larva (Coleoptera: Mordellidae), and during the winter months downy woodpeckers Picoides pubescens (L.).

Distribution of mortality among galls relative to prey (gall) distribution was measured and discussed with respect to the distribution of relative risk of predation.

Galls are by and large contagiously distributed among quadrats, and mortality is distributed in a comparable pattern to that of galls.

The pattern of mortality on Eurosta larvae is neither density‐dependent nor aggregated independently of gall distribution. Persistence in the system is probably a result of a combination of other factors such as adult mortality and early larval death which may have intergenerational density‐dependent effects, and the linkage of locally unstable sub‐populations via migration.
Bionomics of Aphis chloris Koch (Hemiptera: Aphididae) for biological control of St John's wort in Australia
Authors: CSIRO D. T. BRIESE
Published: March 2008

ABSTRACT.

A parthenogenic strain of Aphis chloris Koch, imported into Australia for the biological control of St John's wort Hypericum perforatum L. was found, under laboratory conditions, to develop over a temperature range of 8.5–33°C.

Optimal performance, as measured by fecundity, survival and rm occurred in the range 20–30°C, and at temperatures above 26°C A.chloris performed better than the majority of aphids for which comparable data was available.

Under crowded conditions A.chloris produced smaller apterae, a high proportion of alatae, and a low number of oviparae, but no males. Sexually‐reproducing forms could not be induced under conditions of short photoperiod or low temperatures in the absence of crowding.

Apterae were larger and more fecund when fed on older flowering stems of the host‐plant, than when fed on new rosette growth.

The high potential rate of increase, ability to disperse, and good performance of A.chloris at high temperatures and on the phenological stage of the host‐plant present over summer, suggest that it could contribute to the biological control of St John's wort in Australia, especially during the warmer part of the year when the principal existing control agents (Chrysolina spp.) are inactive.
Coexistence of pseudogamous and sexual planthoppers of the genus Ribautodelphax (Homoptera, Delphacidae)
Authors: den BIEMAN C. F. M.
Published: March 2008

ABSTRACT.

The occurrence of pseudogamous triploid females in populations of the diploid species Ribautodelphax pungens (Ribaut) was studied throughout Europe.

Considerable differences in triploid frequencies were found between populations but no regular geographic pattern was discerned.

Within populations triploid frequencies proved to be stable from generation to generation.

The twofold reproductive advantage of the pseudogamous triploid females is counterbalanced by active mate discrimination by diploid males against the pseudogamous triploid females in populations with high triploid frequencies.

Sexual diploid and pseudogamous triploid females showed no differences in phenology.

Differential winter mortality was found between diploid and triploid larvae.
The intrinsic rates of increase of insects of different sizes
Authors: GASTON K. J.
Published: March 2008

ABSTRACT.

A negative relationship between intrinsic rate of increase, r, and body size has only clearly been shown using data for species drawn from a number of phyla and covering several orders of magnitude in size. Analyses for more closely related species are equivocal.

Data for ninety‐one species of insects, from nine orders, were used to examine the correlation between intrinsic rate of increase and size.

Intrinsic rate of increase was negatively correlated with both length and weight across orders, but no relationship could be shown within orders.

Generation times were positively related to body size, but there was no relationship between net reproductive rate (RQ) and size.

These results support the hypothesis that documented relationships between species size and colonization success in insects could be a consequence of the scaling of intrinsic rate of increase with size.
Body temperature regulation in desert robber flies (Diptera: Asilidae)
Authors: MORGAN KENNETH R. , SHELLY TODD E.
Published: March 2008

ABSTRACT.

We investigated effective thermal environments and behavioural and physiological mechanisms for thermoregulation in two sympatric desert robber flies, Promachus giganteus (Hine) and Efferia texana (Banks). Although similar in body shape and colour, P. giganteus are 4–8 times heavier than E. texana.

During midday, operative temperatures near the ground were substantially higher for P. giganteus (56–73°C) than for E. texana (54–63°C). Correspondingly, P. giganteus generally perched at greater heights above the ground than did E. texana.

Both species maintained thoracic temperatures between 40 and 45°C during most of the day. However, differences between thoracic and abdominal temperatures for individual flies were significantly lower in P. giganteus than in E. texana.

In the laboratory, P. giganteus regulated thoracic temperature by pumping haemolymph into the abdomen. This ability may have accounted for the smaller differences observed between thoracic and abdominal temperatures in P. giganteus and may have allowed this species to search for food and mates during midday when E. texana sought shade.
Endophyte fungus confers resistance to ryegrass: Argentine stem weevil larval studies
Authors: PRESTIDGE R. A. , GALLAGHER R. T.
Published: March 2008

ABSTRACT.

Conferred insect resistance arises from a mutualistic relationship between claviciptaceous endophytic fungi and various grasses. A number of secondary compounds are responsible for the insect resistance. This paper describes studies of the relationship between the endophytic fungus Acremonium lolii Latch, Christensen & Samuels and the Argentine stem weevil Listronotus bonariensis (Kuschel) (Curculionidae); in particular, the effects on larval feeding behaviour, growth and survival.

Larvae are stem borers. Tunnel length and distance bored into the basal sheath zone of ryegrass was reduced when the plants were infected by A. lolii.

Lolitrem B, a potent mammalian neurotoxin, levels were highest in A. lolii infected grasses and ranged from 2.61 to 7.08 μg/g dry wt, the higher value being recorded in summer.

Lolitrem B extracted from A. lolii‐infected perennial ryegrass reduced larval growth rates and survival.

Lolitrem B acted via the insect stomach rather than by absorption through the integument.

The potential role of endophytic fungi in plants is discussed briefly in relation to herbivory.
Honey supplementation and its developmental consequences: evidence for food limitation in a paper wasp, Polistes metricus
Authors: ROSSI A. M. , HUNT J. H.
Published: March 2008

ABSTRACT.

Polistes metricus Say (Hymenoptera: Vespidae, Polistinae) field colonies were supplemented with dilute honey during the pre‐emergence and early post‐emergence phases of colony development.

Supplementation did not increase number of nest cells constructed or rates of loss to predation or foundress disappearance compared with controls.

Colonies receiving honey supplementation produced first offspring earlier in the season than control colonies. The difference is due to a shorter time span between founding and first emergence.

Foundresses of supplemented and control colonies did not differ in wing length or per cent body fat.

Offspring of both supplemented and control colonies had shorter wing lengths than did foundresses of supplemented colonies. Offspring of control colonies had shorter wing lengths than did foundresses of control colonies but not foundresses of supplemented colonies.

The per cent body fat of offspring from control colonies was lower than that of all foundresses and of offspring from supplemented colonies.

The per cent body fat of offspring from supplemented colonies was higher than that of all foundresses.
Distribution and abundance of the intertidal saltmarsh beetle, Bledius spectabilis
Authors: WYATT T. D. , FOSTER W. A.
Published: March 2008

ABSTRACT.

The burrowing intertidal beetle Bledius spectabilis Kraatz (Coleoptera: Staphylinidae) occurs on all but the very youngest marshes on Scolt Head Island, Norfolk, U.K., and may reach densities of up to 4000 m−2 (combined adult and larval densities).

The beetles are restricted to a narrow band about 1m wide along the edges of creeks draining the low marsh areas of the island, and the vertical range is restricted to a zone between 0.8 and 1.55m above Ordnance Datum. The majority of the aggregations and the highest densities are between 1.2 and 1.3m O.D., that is between about 24 and 40cm below MHWN (mean high water at neap tides).

Poor drainage, in particular the presence of long‐standing pools of water over the soil surface, is important in restricting the beetles to well‐drained edge regions.

Transplant experiments suggest that displacement by saltmarsh vegetation, in particular Halimione portulacoides (L.) Aell., sets the upper limit of the beetles’distribution.

The zonation of B.spectablis fits well into the general scheme that has been proposed for the zonation of marine animals from rocky shores.

The beetles produce large (3–6 mm diameter), rapidly draining, abundant (up to 9% of soil volume) and persistent burrows. We suggest that these beetle aggregations may play an important role in the development of the saltmarsh.
Differences between the 7‐spot and 2‐spot ladybird beetles (Coccinellidae) in their toxic effects on a bird predator
Authors: MARPLES NICOLA M. , BRAKEFIELD PAUL M. , COWIE RICHARD J.
Published: March 2008

Abstract. 1. Experiments with nestling blue tits Parus caeruleus L. examined the effects of feeding them 7‐spot ladybird Coccinella septempunctata (L.), 2‐spot ladybird Adalia bipunctata (L.) or controls Tenebrio sp.

2. A feeding rate of 51/3 7‐spot ladybirds per day ‘killed’ nestlings within 2 days. Three of six nestlings fed at half this rate survived 4 days. In contrast, all experimental birds survived sixty‐four 2‐spot ladybirds fed over 4 days (equivalent by weight to the high 7‐spot diet).

3. Nestlings fed 7‐spot ladybirds also grew more slowly than birds fed 2‐spot ladybirds. The latter birds showed no difference in weight gain from the controls although they begged more strongly for food.

4. Cadavers of birds fed 7‐spot ladybirds showed evidence of severe liver damage.

5. The results indicate a substantial difference between the ladybird species in their toxicity to nestling blue tits. They support the hypothesis that 2‐spot ladybirds are largely‐edible, polymorphic Batesian mimics of well‐protected, monomorphic species such as the 7‐spot ladybird.
The roles of temperature and diapause in the life history of a temperate‐zone dragonfly: Argia vivida (Odonata: Coenagrionidae)
Authors: PRITCHARD GORDON
Published: March 2008

Abstract. 1. The life cycle of Argia vivida Hagen generally took longer to complete in the field than was predicted on the basis of the thermal sum accumulated in laboratory rearing.

2. The prediction of a bivoltine life‐cycle from geothermal sites with either a constant annual temperature of 26°C or thermal range of 11–31°C was not borne out because the intervention of short‐day induced developmental delays in later larval instars extended the life cycle to 1 year.

3. This diapause, which synchronizes adult emergence with favourable summer temperatures, was also present in larvae from sites with annual temperature ranges of 0–33°C and 5–20°C.

4. At these colder sites completion of the life cycle takes 2 and 3 years respectively and dragonflies must be in cold‐resistant stages during the winter. A long‐day diapause, principally affecting late‐instar larvae below a certain size during the summer, achieves this.

5. Large diurnal temperature fluctuations at the 0–33°C site markedly increase the useful thermal energy available to larvae for growth over that predicted by the thermal sum equation.

6. The interaction between the effects of temperatures favourable for growth and day‐length‐governed diapause, synchronize the emergence of the low‐temperature sensitive adult stage of this tropical dragonfly with northern‐latitude summers at a variety of habitats.
Oviposition site preference and larval mortality in a leaf‐mining moth
Authors: AUERBACH MICHAEL , SIMBERLOFF DANIEL
Published: March 2008

Abstract. 1. The univoltine leaf‐mining moth, Lithocolletis quercus Ams., is endemic to Israel, where it spends its 10.5 month larval period feeding only in the leaves of Quercus calliprinos Webb.

2. We compared patterns of egg deposition and sources of larval mortality to test whether oviposition patterns and site preferences confer an enhanced likelihood of larval survival.

3. Dominant sources of larval mortality were premature leaf abscission and death from unknown causes, whereas predation, parasitism and intraspecific interference accounted for relatively little larval mortality.

4. Eggs, and thus mines, were aggregated among leaves of host trees even though premature leaf abscission was positively correlated with density of mines per leaf. Interference competition among larvae was the only other density‐dependent mortality factor.

5. Oviposition patterns within leaves mitigated the probability of death from larval interference, and probably also from early leaf abscission.

6. Despite these density‐dependent mortality factors, overall probability of larval survival to pupation was independent of initial density of mines on a leaf.

7. The long larval period allows synchrony between oviposition flights and times of predictable resource availability.
The influence of host distribution, sex, and size on the level of parasitism by Itoplectis conquisitor (Hymenoptera: Ichneumonidae)
Authors: CRONIN JAMES T. , GILL DOUGLAS E.
Published: March 2008

Abstract. 1. Parasitism of the bagworm, Thyridopteryx ephemeraeformis Haw. (Lepidoptera: Psychidae), on red cedar was studied at Manassas, Va., U.S.A.

2. Fifteen parasitoids, five of which were hyperparasitoids, attacked the pupal stage of the bagworm. The Ichneumonid Itoplectis conquisitor alone accounted for 58% of the parasitized bagworms.

3. Parasitism by I conquisitor (Say) was inversely related to host size, but independent of host distribution within a tree. Male bagworms experienced disproportionately higher levels of parasitism than females. We conclude that it is small size that renders bagworms susceptible to parasitism rather than sex per se.

4. Ovipositor lengths of I.conquisitor were insufficient to penetrate the larger bagworm hosts (>57 mm); and in fact, as bagworm size increased, the proportion of the I.conquisitor population capable of penetrating the pupa declined abruptly. We suggest that the mechanical difficulties with oviposition, and perhaps the defensive capabilities of larger hosts, are responsible for the relationship between host size and per cent parasitism.

5. I.conquisitor could be an important selective agent for bagworm size at pupation, but it is not likely to act as a significant control agent of population density.
Dynamic information and host acceptance by a tephritid fruit fly
Authors: MANGEL MARC , ROITBERG BERNARD D.
Published: March 2008

Abstract. 1. Female apple maggot (Rhagoletis pomonella Walsh) flies held in field cages usually oviposited in an unparasitized (non‐pheromone marked) fruit when it was encountered.

2. Oviposition in a previously parasitized (pheromone marked) fruit depended upon the time since the last oviposition (TSLO) and the percentage of infested fruit encountered during search for oviposition sites.

3. Previous theories of host acceptance suggest that the acceptance or rejection of a host should depend dichotomously on time since last oviposition and the fraction of marked hosts in the last five encounters. The experiments, however, show considerable variability and are thus not consistent with the theory.

4. A new theory for the experiments is introduced. This model involves physiological (egg complement) and informational state variables and leads to intuitive understanding of the experimental results. In particular, the model shows how the plasticity in oviposition site selection may arise from fitness maximizing behaviour. Alternative models are also discussed. All of the models stress the importance of physiological and informational states.
Soil softness, nest initiation and nest sharing in the wasp, Cerceris antipodes (Hymenoptera: Sphecidae)
Authors: McCORQUODALE D. B.
Published: March 2008

Abstract. 1. The relationship between soil softness and nest initiation was studied at two aggregations of a ground nesting sphecid wasp, Cerceris antipodes Smith, in New South Wales, Australia.

2. Nests of C.antipodes were initiated throughout the active season. Nests were started more frequently during moist conditions and when more wasps were active.

3. Nest initiation was clumped on days after periods of rain. Nest initiation was only observed when the soil was soft.

4. Two experimental plots that were watered had significantly softer soil and more nests initiated on them than two control plots. Searching female wasps spent considerably more time on the watered plots than the controls.

5. Nest initiation through hard surface soils presents a problem to C.antipodes. Soil softness must be considered in any analysis of nest sharing in this species.
Effects of changing photoperiods in the life cycle regulation of the comma butterfly, Polygonia c‐album (Nymphalidae)
Authors: NYLIN SÖREN
Published: March 2008

Abstract. 1. Regulation of adult reproductive diapause and seasonal polyphenism was studied in two populations of the comma butterfly, Polygonia c‐album (L.) (Nymphalidae), from Stockholm, Sweden, and Oxford, England.

2. In the univoltine Stockholm population short and long constant day‐lengths (in the range 12–22 h) at 20°C were ineffective in averting the production of the dark, generally diapausing, morph, but the non‐diapausing light morph could be produced if daylengths were increased during larval development. The procedure was especially effective with increases from 12 to 22 h, but the tendency was the same with a more realistic increase, from 18 to 20 h.

3. In the partially bivoltine English population a critical constant day‐length for morph and diapause induction was found between 12 and 18 h. Decreasing daylengths above the critical daylength early or late in larval development resulted in production of the diapausing morph.

4. These results suggest a system for environmental control where day‐lengths which increase throughout the larval period indicate an early date before summer solstice, meaning that there is sufficient time for a second generation of offspring to reach the hibernating adult stage before winter. The ecological significance of the results is discussed.
An analysis of the deterrent effect of aphids on cabbage root fly (Delia radicum) egg‐laying
Authors: FINCH S. , JONES T. H.
Published: March 2008

Abstract. 1. The cabbage root fly, Delia radicum (L.), was deterred from laying eggs on brassica plants with >250 cabbage aphid, Brevicoryne brassicae (L.), or peach‐potato aphid, Myzuspersicae (Sulz.).

2. Flies did not lay on plants infested with >250 aphids.

3. Preparations of (E)‐β‐farnesene, the aphid alarm pheromone, deterred the flies from laying only at the extremely high dose of 32 mg/plant.

4. Although M. persicae secreted large (1 ng/insect) amounts of alarm pheromone and B. brassicae extremely small (<0.01 ng/insect) amounts, both aphids equally deterred D. radicum from laying.

5. The deterrent effect appeared to result from the aphids physically disturbing the flies during host‐plant selection.
Secretion‐grooming in the water bug Plea minutissima: a chemical defence against microorganisms interfering with the hydrofuge properties of the respiratory region
Authors: KOVAC D. , MASCHWITZ U.
Published: March 2008

Abstract. 1. The water bug Plea minutissima Leach (Hemiptera: Pleidae) from time to time crawls out of the water and distributes secretion from its metathoracic glands over the ventral part of its body. By this ‘secretion‐grooming’ antiseptic gland substances, mostly hydrogen peroxide, are applied to the hydrofuge hairs which hold the respiratory air bubble.

2. When the bugs are prevented from leaving the water, their mortality increases significantly, and individuals lacking the air bubble are observed. Examination of such bugs with Scanning Electron Microscopy techniques reveals bacteria growing on their hydrofuge hairs, whereas in bugs allowed to secretion‐groom the hairs are not contaminated by microorganisms.

3. Artificial application of diluted metathoracic gland secretion on the body surface of P. minutissima kills bacteria, while specific ciliates, which never colonize the respiratory region, are not harmed by the secretion.

4. It can be concluded that secretion‐grooming prevents the contamination of the hydrofuge respiratory region that leads to the wetting of the hydrofuge respiratory regions, resulting in the loss of the air bubble, and, finally, the drowning of the animals.

5. Other possible functions of the secretion, such as chemical defence against predators or wetting of the body surface, could not be demonstrated or seem unlikely.