bluuebunny/crossref_metadata_2025 huggingface dataset:
Increase in cold‐shock tolerance by selection of cold resistant lines in Drosophila melanogaster
Authors: CHEN C‐P. , WALKER V. K.
Published: March 2008

Abstract.

In Drosophila melanogaster, the cold‐shock tolerance of adult flies at ‐7°C increased 22% after a prior 2h exposure to 4°C as measured by LD50, the dose (degree minutes of exposure to subzero temperature) which resulted in 50% mortality.

Cold‐shock tolerance was further significantly increased by selecting cold resistant lines by exposure of adults (1) to 4°C for 2 h (short‐term chilling), or (2) to ‐7°C for 80–120 min (cold shock), or (3) to short‐term chilling followed by cold‐shock.

After ten generations of selection, the greatest increase in cold‐shock tolerance was found in flies selected using the combined exposure of short‐term chilling and cold shock. LD50s increased 33% in comparison with the unselected control strain when no chilling pre‐treatment was given prior to cold shock at ‐7°C.

The rapid cold‐hardening response increased 82% in the line selected by the short‐term chilling and cold‐shock regime.

The enhanced cold‐shock tolerance was relatively stable since no decrease was observed after four generations without selection.

This report shows the role of short‐term adaptation as well as selection in the capacity to survive low temperatures in non‐diapausing stages of insects.
Choice of flowers by foraging honey bees (Apis mellifera): possible morphological cues
Authors: DUFFIELD G. E. , GIBSON R. C. , GILHOOLY P. M. , HESSE A. J. , INKLEY C. R. , GILBERT F. S. , BARNARD C. J.
Published: March 2008

Abstract.

Honey bees foraging for nectar on lavender (Lavandula stoechas) chose inflorescences with more of their flowers open. The number of open flowers predicted whether an inflorescence was visited by bees, inspected but rejected, or ignored. Inflorescences chosen arbitrarily by observers had numbers of open flowers intermediate between those of visited and ignored inflorescences.

Differences in morphological characters between types of inflorescence correlated with nectar volume and sugar weight per flower so that visited inflorescences had a disproportionately greater volume of nectar and weight of sugar per flower and greater variance in nectar volume.

Although there were significant associations between nectar content and the morphological characters of inflorescences, discriminant function analysis revealed discrimination on the basis of morphology rather than nectar content.

Visited inflorescences tended to have smaller than average flowers but bees tended to probe the largest flowers on visited inflorescences.

Choice of flowers within inflorescences is explicable in terms of the relationship between flower size and nectar content.
Evidence for mutualism between a flower‐piercing carpenter bee and ocotillo: use of pollen and nectar by nesting bees
Authors: SCOTT PETER E. , BUCHMANN STEPHEN L. , O'ROURKE MARY KAY
Published: March 2008

Abstract.

Carpenter bees (Xylocopa californica arizonensis) in west Texas, U.S.A., gather pollen and ‘rob’ nectar from flowers of ocotillo (Fouquieria splendens). When common, carpenter bees are an effective pollen vector for ocotillo. We examined ocotillo's importance as a food source for carpenter bees.

The visitation rate of carpenter bees to ocotillo flowers in 1988 averaged 0.51 visits/flower/h and was 4 times greater than that of queen bumble bees (Bombus pennsylvanicus sonorus), the next most common visitor. Nectar was harvested thoroughly and pollen was removed from the majority of flowers. Hummingbird visits were rare.

Pollen grains from larval food provisions were identified from sixteen carpenter bee nests. On average, 53% of pollen grains sampled were ocotillo, 39% were mesquite (Prosopis glandulosa), and 8% were Zygophyllaceae (Larrea tridentata or Guaiacum angustifolium). Carpenter bee brood size averaged 5.8 per nest.

We measured the number of flowers, and production of pollen and nectar per flower by mature ocotillo plants, as well as the quantity of pollen and sugar in larval provisions. An average plant produced enough pollen and nectar sugar to support the growth of eight to thirteen bee larvae. Ocotillo thus has the potential to contribute significantly to population growth of one of its key pollinators.

Although this carpenter bee species, like others, is a nectar parasite of many plant species, it appears to be engaged in a strong mutualism with a plant that serves as both a pollen and as a nectar source during carpenter bee breeding periods.
Extreme adaptive life‐cycle in a high arctic aphid,Acyrthosiphon svalbardicum
Authors: STRATHDEE A. T. , BALE J. S. , BLOCK W. C. , WEBB N. R. , HODKINSON I. D. , COULSON S. J.
Published: March 2008

Abstract.

The year‐round biology of a high arctic aphid is described for the first time.

The life‐cycle is shown to be genetically determined, and thus markedly different to temperate species where the observed polymorphism is governed primarily by external environmental cues.

The fundatrix, which emerges from the overwintering egg, gives birth directly to sexual morphs, a phenomenon previously undescribed in the Aphidinae. This process is essentially prevented in temperate aphids by an endogenous mechanism, the interval timer.

In addition to the sexual morphs, the fundatrix produces a small number of parthenogenetic individuals (viviparae) that give rise to a third generation. This last generation consists exclusively of oviparae and males that would increase the number of overwintering eggs provided there is sufficient thermal budget for them to mature and oviposit before conditions become adverse.

The position of particular morphs in the birth sequences of the second and third generations maximize the chances of survival in harsh conditions, whilst enhancing the likelihood that individuals from the third generation will add to the number of overwintering eggs.

Guaranteed egg production combined with an in‐built flexibility to produce an extra generation in particularly favourable seasons, confer adaptations to the high arctic environment, and ideally suit this aphid to exploit elevated temperatures in an era of climate change.
Seasonality and life cycles of woody plant‐feeding noctuid moths (Lepidoptera: Noctuidae) in Mediterranean habitats
Authors: YELA JOSÉ L. , HERRERA CARLOS M.
Published: March 2008

Abstract.

The annual cycle of noctuid moths feeding as larvae on the foliage of eighteen woody plant species (belonging to ten different families) was studied at two southeastern Spanish Mediterranean forest habitats. Two questions were addressed in this study. (1) Does the rigorous (hot and dry) summer season characteristic of the Mediterranean‐type climate impose a constraint on noctuid life histories? (2) Are there detectable differences in abundance or phenological patterns between the noctuid assemblages feeding on evergreen and winter‐deciduous trees and shrubs?

Regardless of their leaf persistence habit, the majority of woody species studied had short shoot growth and leaf production periods in spring. Abundance of noctuid larvae peaked in May‐June, shortly after host plants started to produce new leaves. Virtually no noctuid larvae were found on the foliage of the woody species studied at other times of year. Abundance and seasonal pattern of occurrence of larvae were similar on evergreen and deciduous food plants.

In contrast with the unimodal seasonal pattern exhibited by larvae, the abundance of adult moths (assessed by light trapping) showed two distinct peaks in early summer and early autumn, and a marked minimum in mid‐summer.

Most woody plant‐feeding noctuids recorded in this study (86% of species, about 95% of individuals) were univoltine. Univoltine species fell into one of two distinct life history categories, corresponding to pre‐ and post‐summer flight periods. These two contrasting phenologies were associated with a bimodality in the duration of the pupal stage (‘short’ versus ‘long’), and were closely related to taxonomical affiliation at the subfamily level.

Within the ‘short’ pupal duration group, some species mate and oviposit shortly after emergence and pass the dry season in the egg stage, while others remain as potentially active, non‐reproductive adults over most of the summer and mate by the end of that season. Species in the ‘long’ pupal duration group pass the summer in pupal or prepupal stage.

In the Mediterranean habitats studied, the adversity of the summer dry season seems to have led to a woody plant‐feeding noctuid species assemblage almost entirely made up of univoltine species that concentrate their larval phases when suitable food (young leaves) is most abundant, and ‘avoid’ mid‐summer as a flight time by emerging either shortly before or shortly after the adverse summer drought period. Year‐round foliage availability afforded by dominant evergreen plants does not seem to have influenced the seasonal organization of noctuid cycles in any substantial way.
Effect of host availability on reproduction and survival of the parasitoid wasp Trichogramma minutum
Authors: BAI B. , SMITH S. M.
Published: March 2008

Abstract.

We tested the hypothesis that females of the egg parasitoid, Trichogramma minutum Riley (Hymenoptera: Trichogrammatidae), could adjust their fecundity schedule according to host availability and that there was a negative correlation between reproduction and survival in these wasps.

Newly‐emerged females were provided with an unlimited or limited number of hosts in the first trial and with either unlimited, limited or zero hosts in the second trial.

When hosts were unlimited, wasps had the highest rate of reproduction in the first day, which decreased dramatically thereafter. When hosts were limited, wasps from the two trials differed in their response. In Trial I, females with limited hosts had lower first‐day fecundity than, and the same subsequent‐day fecundity as, those with unlimited hosts. However, in Trial II, females with limited host had a lower first‐day but a higher subsequent‐day fecundity than those with unlimited hosts. This indicates variation in Trichogramma's ability to shift its fecundity schedule in response to host availability.

There was a positive (rather than a negative) correlation between reproduction and survival. Wasps that oviposited (in host‐unlimited treatment) had greater longevity than those that could not (in host‐unavailable treatment).

The sex ratio of the progeny produced by wasps in both host‐unlimited and limited treatments shifted gradually from a female to a male bias as the wasps aged.

We consider the ability of parasitoids to adjust their fecundity schedule as an adaptation to changing host resources and discuss our findings with regard to theories of life history evolution.
Mutual use of leaf‐shelters by lepidopteran larvae on paper birch
Authors: CAPPUCCINO NAOMI
Published: March 2008

Abstract.

Many species of birch‐feeding Lepidoptera make leaf‐shelters by tying leaves together with silk. Several species, or several instars of a single species, may be found together within a single leaf‐shelter.

Shelters made in June by the birch tube‐maker Acrobasis betulella (Pyralidae) are colonized throughout the season by other Lepidoptera. Artificial A.betulella shelters, made by tying leaves together with string, were colonized at a greater rate than nearby control foliage, indicating that secondary species are indeed responding to the presence of the shelter, and not to some other aspect of plant quality.

Several species in the families Oecophoridae, Gelichiidae and Stenomidae make ‘leaf‐sandwiches’ by tying two leaves together; these are later colonized by oviposition from adult A.betulella. Artificial sandwiches made by joining leaves together with paperclips were colonized by several species of sandwich‐makers, as well as by A.betulella. Colonization occurred mainly via oviposition, although some sandwiches may have been colonized by wandering larvae.

First instar A.betulella, which cannot form their own shelter, enjoyed greater survivorship when placed in artificial leaf‐sandwiches than when placed on leaves without sandwiches.
Superparasitism and mutual interference in the egg parasitoidAnagrus delicatus(Hymenoptera: Mymaridae)
Authors: CRONIN JAMES T. , STRONG DONALD R.
Published: March 2008

Abstract.

In nature, interference amongAnagrus delicatus(Hymenoptera: Mymaridae) parasitoids reduced the per‐capita number of hosts parasitized. Interference increased with parasitoid density.

Anagrus delicatusdid not avoid parasitizing hosts that had recently been parasitized by conspecific wasps. Evidence indicated that this superparasitism was largely a random process, increasing with the ratio of parasitized to unparasitized hosts.

Individual parasitoid efficiency, the number of hosts killed per wasp per unit time, decreased with increasing wasp density. This occurred whether wasps searched the patch together (simultaneously) or one by one (sequentially), and was the result of an increase in time spent superparasitizing hosts at higher wasp density. This is known as indirect mutual interference.

Increasing numbers of parasitoids together on the same patch caused a significant decline in the rate and per‐capita number of hosts parasitized. However, there was not a correspondent decline in searching efficiency with increasing wasp density (i.e. no direct mutual interference).

These forms of parasitoid density dependence should contribute to the stability of the host—parasitoid interaction.
Self and conspecific superparasitism by the solitary parasitoid Antrocephalus pandens
Authors: GATES SIMON
Published: March 2008

Abstract.

The fitness consequences of superparasitism for a solitary parasitoid depend on whether the host was first parasitized by itself (‘self‐superparasitism’) or a different individual (‘conspecific superparasitism’). Self superparasitism is usually expected to be avoided.

A.pandens females showed no difference in their probability of superparasitism between self‐parasitized and conspecifically‐parasitized hosts. The probability of superparasitism decreased as time from the laying of the first egg in a host increased, from about 0.29–0.46 at a time interval of 1 h to 0.10–0.14 at 72 h.

The egg distribution of wasps foraging alone on a patch showed significant avoidance of superparasitism, but that of wasps foraging in the presence of conspecifics was not significantly different from a random distribution. This suggests that wasps switch from avoidance of superparasitism when alone to acceptance of all hosts when in a group.

When wasps foraged in a group, the hosts had many more ovipositor puncture marks than when wasps foraged singly. This suggests that either hosts were attacked several times per encounter, or that the wasps' encounter rate with hosts was much higher when in a group. If the latter is true, it is possible that, although the egg distribution suggested a higher rate of superparasitism when wasps foraged in a group, the ratio of acceptances to contacts of parasitized hosts may in fact have been lower.
Mate finding, dispersal, number released, and the success of biological control introductions
Authors: HOPPER KEITH R. , ROUSH RICHARD T.
Published: March 2008

Abstract.

An analysis of published data and a mathematical model of the population dynamics of introduced parasitoids were used to explore the possibility that biological control introductions fail because an Allee effect drives small, introduced populations extinct. Such an Allee effect would arise because low densities, resulting from dispersal into a new environment, lead to failure to mate, which leads to a male‐biased sex ratio, which, if extreme enough, could cause population extinction.

For chalcidoids, ichneumonoids and tachinids, the proportion of parasitoid populations that established when introduced for control of lepidopteran pests increased with the number of parasitoids per release, the total number released, and the number collected when each variable was analysed separately. For chalcidoids alone, establishment increased with the number of releases for this variable analysed separately. However, stepwise logistic regression of establishment on these variables included only the total number released for chalcidoids and the number per release for ichneumonoids and tachinids. This suggests that an Allee effect may limit the establishment of introduced parasitoids more than stochastic environmental variation or lack of genetic variation.

A reaction‐diffusion model of parasitoid introductions was developed, which included mate finding, dispersal, reproduction and survival. Sensitivity analysis showed that the critical number of females needed to establish a population decreased hyperbolically as mate detection distance and net reproductive rate were increased, but the critical number increased linearly as mean‐square displacement was increased. The critical number of females did not change when the gross distance traversed per generation was varied. This was because increased area searched by males compensated for increased displacement. Changing from virgin females producing all males (arrhenotoky) to virgin females producing no progeny increased the critical number of females by over 30%.

The analysis of past introductions and the sensitivity analysis of the reaction‐diffusion model both suggested a threshold of about 1000 insects per release to ensure establishment of introduced parasitoids. The implications of our results for the design of biological control introductions are discussed. Limitations in retrospective analyses and current knowledge indicate the need for an experimental approach to introductions.
Leaf miners on Ochna ciliata (Ochnaceae) growing on Aldabra Atoll: patterns of herbivory in relation to goat browsing and exposure to the sun
Authors: LINFIELD MARK C. J. , RAUBENHEIMER DAVID , HAMBLER CLIVE , SPEIGHT MARTIN R.
Published: March 2008

Abstract.

The patterns of herbivory by leaf miners on the shrub Ochna ciliata growing on Aldabra Atoll were studied in relation to browsing by feral goats and exposure to the tropical sun versus shading.

Damage due to both tunnelling (Diptera) and ‘blotch‐making’ (Lepidoptera) leaf miners was statistically greater on trees that had been browsed and on those that received more extensive exposure to the sun.

Effects of exposure and browsing were additive, as evidenced by the lack of statistical interaction between these factors.

There was a significant negative correlation between the numbers of tunnelling and blotch‐making miners in trees that had been browsed, but not in unbrowsed trees.

Three geographical areas were sampled to test whether the effects of browsing on leaf mining were invariant or influenced by as yet unknown environmental factors. A statistically significant interaction between browsing and geographical region indicated that, while browsed trees had significantly more mines whatever the habitat, the extent of this effect differed across the habitats.
Influence of intra‐tree variation in time of budburst of white spruce on herbivory and the behaviour and survivorship of Zeiraphera canadensis
Authors: QUIRING DAN T.
Published: March 2008

Abstract.

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

There was significant variation in the time of budburst among whorls, shoots and buds. Budburst was acropetal, with buds in the interior of the lower crown bursting first and terminal buds on terminal shoots in the upper crown bursting last.

Bud moths laid the greatest proportion of their eggs in the middle of the crown and egg hatch was usually best synchronized to budburst in this region. Many eggs hatched before terminal buds on terminal shoots in the upper crown had burst and thus intra‐tree variation in budburst decreased the probability that first‐instar larvae would colonize the most important plant parts for growth.

However, many later instars dispersed upwards and outwards in the crown and colonized the late bursting buds in the upper crown. Such dispersal reduces the effectiveness of intra‐plant variation in budburst to reduce herbivory and permits Z.canadensis to eat young nutritious buds for a longer period of time.

Intra‐tree variance in the date of budburst was greater than that between trees but there were no consistent differences between the intra‐tree variance of trees in half‐sib families with high or low susceptibility to Z.canadensis. Differences between trees in herbivory, bud moth density and survivorship were not related to the amount of intra‐tree variation in budburst.
Population dynamics of the yew gall midge Taxomyia taxi and its chalcid parasitoids: a 24‐year study
Authors: REDFERN M. , CAMERON R. A. D.
Published: March 2008

Abstract.

The dynamics of three populations of Taxomyia taxi (Inchbald) (Diptera: Cecidomyiidae) and its chalcid parasitoids have been studied over a 24‐year period. Most individuals have a 2‐year life cycle but some develop in 1 year. Details of within‐generation mortalities in T.taxi are used for life table analyses.

Mortality in the period between emergence of adult T.taxi and larval infestation of buds appears to be density‐dependent and is the largest component of overall mortality. In 2‐year life cycles, this mortality and that caused by Torymus nigritarsus (Walker) contribute equally to variance in overall mortality. In 1‐year cycles, mortality caused by Mesopolobus diffinis (Walker) is density‐dependent and accounts for most within‐gall losses.

T. nigritarsus, which attacks only 2‐year galls, is absent from all populations for a number of years in the middle of the study period. Its searching efficiency declines as its density and that of its host increase.

Densities of M.diffinis are strongly correlated with those of available hosts. Percentage parasitism of 2‐year galls is less than that of 1‐year galls, suggesting the occurrence of enemy‐free space.

Although there are some correlations in densities and mortality between trees, the dynamics of populations on each are frequently different.

An earlier analysis of 10 years' data failed to demonstrate density‐dependent effects. The extension to a 24‐year run has revealed such effects, but also demonstrates long‐term fluctuations in population densities, with corresponding changes in the balance of advantage between 1‐ and 2‐year life cycles of T.taxi.
Oviposition habitat selection by the mosquito, Culiseta longiareolata: effects of conspecifics, food and green toad tadpoles
Authors: BLAUSTEIN LEON , KOTLER BURT P.
Published: March 2008

Abstract. 1. Ovipositing females should choose egg‐laying sites which maximize the growth and survivorship of their offspring. Accordingly, they should avoid habitats with high densities of competitors and predators and should choose sites with adequate food. We tested experimentally the oviposition response of the mosquito, Culiseta longiareolata Macquart, to extra food and two species which are both potential competitors and predators of its offspring: conspecific larvae and green toad (Bufo viridis) tadpoles.

2. We conducted the experiment in outdoor artificial pools where wild C. longiareolata females were presented with choices of all combinations of the presence or absence of: (1) C.longiareolata larvae, (2) B.viridis tadpoles, and (3) extra food (a mixture of ground fish food and mouse chow).

3. Oviposition rates averaged approximately 4 times greater in response to extra food.

4. The presence of the tadpoles, particularly later in the experiment when they were larger, caused a significant reduction (approximately 50%) in oviposition rate.

5. We did not detect a statistically significant effect of conspecific larvae on oviposition habitat selection.

6. Our results indicate that Culiseta females choose habitats for oviposition based on food availability. They also tend to avoid habitats containing Bufo tadpoles, presumably to avoid predation and/or competition.
Complex dynamics of desert locust plagues
Authors: CHEKE ROBERT A. , HOLT JOHNSON
Published: March 2008

Abstract. 1. Spectral analysis of 66 years of locust swarm abundance data failed to reveal any significant cycles although the dominant cycle detected in a de‐trended series, adjusted to take account of a significant partial autocorrelation for a lag of 1 year, had a periodicity of 16 years.

2. Although some estimates of the intrinsic rate of increase (r) of desert locusts are indicative of chaos, reconstructions of locust dynamics using response surface methodology (RSM) suggested exponential stability. This was also true for data for the West African Region alone and inclusion of rainfall data from the Sahel improved the significance of an RSM model for West Africa.

3. The observed positive relationship between locust abundance and rainfall in West Africa confirmed the importance of rain; but the variance of the locust abundance also increased with rainfall, making rainfall alone a poor predictor. However, this heteroscedastic pattern was reproducible by a simple logistic model with a chaotic r and a variable K. This was not the case when a stable value for r was used.

4. The available data and current methodologies are insufficient to provide unequivocal conclusions on locust dynamics, which are complicated by phase changes and associated switches in r values.
The natural dynamics of the eulophid parasitoid Melittobia australica
Authors: FREEMAN B. E. , ITTYEIPE K.
Published: March 2008

Abstract. 1. The ecology of the eulophid parasitoid Melittobia australica Girault was studied in the laboratory and field in Jamaica. Further field observations were conducted in Trinidad.

2. The sphecid, mud‐daubing wasp Sceliphion assimile (Dahlbom) was the main host in Jamaica, but nineteen out of twenty‐two investigated species of sphecid, eumenid and pompilid wasps, and apid and megachilid bees were attacked in Jamaica and Trinidad. The nineteen susceptible hosts suffered an average of 23.6% mortality due to Melittobia. Resin is a totally effective deterrent, spaces within the nest less so.

3. Laboratory studies on Sceliphron hosts estimated that developmental survival was greatest at 26°C and 83% r.h., duration of development shortest at 32°C and 72% r.h., longevity of adult fliers greatest (>13 days) at <25°C and 80% r.h., and fecundity greatest (454 eggs/female) at 28°C and 90% r.h. A separate experiment gave a maximum fecundity of 461.

4. At 27°C and 71% r.h. the duration of development (egg‐adult) in the laboratory was 13.1 days for males, 13.9 days for crawlers and 17.4 days for fliers.

5. Field studies showed that developmental mortality was low, while laboratory studies revealed it to be density dependent, ranging from 13% at the lowest densities to 39% at the highest. Estimated mortality at field densities was ∼25% on Sceliphron.

6. Field estimates of fecundity gave a mean of 429.5 eggs/female on Sceliphron but are positively biased by superparasitism. Fecundity is probably reduced to about 346 eggs in the field and further to about 289 as a result of superparasitism. Other hosts generally reduced the parasitoid's fecundity, and this always occurs when Melittobia becomes a hyperparasite.

7. Superparasitism in the field on Sceliphron was 2.3 females/host for crawler morph females, 1.2 females/host for jumper females and 1.2 females/host for flier females.

8. A cyclic budget using log10K; values (Freeman, 1976) revealed that the effect of superparasitism (K0= 0.124), the physical environment (K0= 0.078), developmental mortality (K1= 0.125), and the loss to males (K2= 0.020) to be small, but losses of dispersing females (k3= 2.326) to be massive.

9. The individual chance for the three female morphs of finding a new host are very different. For crawlers (which search the natal host nest) it is 0.034 (1 in 29), for jumpers (which search the host nesting site) it is 0.0098 (1 in 102) and for fliers (which seek distant host nesting sites) 0.0021 (1 in 485). Risk is thus directly proportional to distance travelled (cm, m and km). Morph production is related to this risk.
Climatic adaptations in the Drosophila immigrans species group: seasonal migration and thermal tolerance
Authors: KIMURA MASAHITO T. , BEPPU KATSURA
Published: March 2008

Abstract. 1. In central Japan, Drosophila curviceps Okada and Kurokawa was collected in spring and autumn but not in summer at lowlands (alt. 500–1200 m), while it was collected only in summer at highlands (1500–2000 m). Experiments on its thermal tolerance suggested that summer heat at the lowlands and winter low temperatures at the highlands were adverse to this species. It is considered that this species escapes from these extreme temperatures by undergoing seasonal migration between the lowlands and the highlands. This species had no photo‐periodic diapause and bred at both lowlands and highlands.

2. D.immigrans Sturtevant was less cold‐hardy but more heat‐tolerant than D.curviceps. It is considered that this species is unable to overwinter outdoors at least in the study areas (i.e. alt. 500m or higher in central Japan) and its populations in these areas originate with migrants from warmer areas.

3. D.albomicans Duda, a subtropical species, was less cold‐hardy but more heat‐tolerant than the above two species.

4. Climatic adaptations and distributions of these species are discussed with reference to their thermal tolerance.
The influence of Salix leaf abscission on leaf‐miner survival and life history
Authors: PRESZLER RALPH W. , PRICE PETER W.
Published: March 2008

Abstract. 1. Early abscission of mined leaves was an important mortality factor of a Phyllonorycter species (Lepidoptera: Gracillariidae) on Salix lasiolepis Benth. (Salicaceae). A larger percentage of mined leaves abscised early (34.4% in 1990; 24.5% in 1991), and Phyllonorycter survival was greatly reduced in these abscised leaves.

2. Leaf‐mining by Phyllonorycter was associated with increased early leaf abscission. An egg removal experiment demonstrated that leaf mining induced this increase in leaf abscission.

3. The induction of early leaf abscission was dependent upon the timing of herbivory and simulated herbivory (mechanical damage). Early mechanical damage induced leaf abscission, late mechanical damage did not. Mines which expanded early were more likely to induce leaf abscission than mines which expanded more slowly.
Resource limitation and the lethal and sublethal effects of a viral pathogen in the Indian meal moth, Plodia interpunctella
Authors: BOOTS MICHAEL , BEGON MICHAEL
Published: March 2008

Abstract.

The effects of resource limitation and the lethal and sublethal effects of a granulosis virus on a lepidopteran host, the Indian meal moth, Plodia interpunctella, were examined.

The food quality was manipulated by the addition of an inert bulking agent (methyl cellulose) which caused the size, development rate and fecundity of the moths to be reduced.

The resource quality had no effect on the mortality due to the virus. In contrast, sublethal effects of the virus on pupal weight were more apparent under conditions of resource limitation.

Considerable variation between the sublethal effects after challenge with different doses of the virus was found. The balance between deleterious sublethal effects of the virus and the selection of more robust individuals by the bioassays is proposed as a mechanism to explain this variation.

Implications for the dynamics of insect hosts and their pathogens are discussed.
Density‐related foraging behaviour in Closterocerus tricinctus, a parasitoid of the leaf‐mining moth, Cameraria hamadryadella
Authors: CONNOR EDWARD F. , CARGAIN MICHELE J.
Published: March 2008

We examined the foraging behaviour of the parasitoid wasp, Closterocerus tricinctus (Ashmead) (Chalcidoidea: Eulophidae), as it visited larvae of the leaf‐mining moth, Cameraria hamadryadella (Lepidoptera: Gracillariidae), in an outbreak population.

We tracked females of C.tricinctus, recording the time spent searching for mines and handling host larvae. The density of leaf‐mines (host larvae) and their condition were recorded for each leaf visited. A subset of leaves visited by C.tricinctus was enclosed in fine mesh bags so that foraging success could be determined by rearing or dissection. The average density of mines and the average leaf‐area mined was estimated for a random sample of leaves from each tree.

The selection of leaves upon which to forage appears to be density‐dependent. C.tricinctus visits leaves with leaf‐mine densities twice the average, and when switching leaves lands directly on leaf‐mines 5 times more often than expected assuming random landings.

The total time spent foraging on a leaf, the average time spent handling hosts, and the total search time within leaves tend to decline on leaves with many hosts, but the observed declines are not statistically significant.

The proportion of leaf‐mines visited within a leaf is strongly inversely density‐dependent. 30% of visits to leaf‐mines are re‐visits and 29% of handling time is spent re‐handling previously visited hosts. Furthermore, only 21% of visits to mines lead to successful parasitism. We suggest that self‐interference and the avoidance behaviour of the host may reduce the number of visits of leaf‐mines by C.tricinctus within a leaf.

The effect of the strongly inversely density‐dependent foraging investment within leaves is to offset the observed density‐dependent pattern of leaf visitation making the overall spatial pattern of visitation by C.tricinctus to mines of C.hamadryadella inversely density‐dependent.

We suggest that the uncertainty of C.tricinctus surviving on multiply mined leaves because of density‐dependent host mortality due to intraspecific competition in high‐density host populations, the rarity of high‐density host populations, and the rarity of multiply‐mined leaves in low‐density host populations combine to select against an aggregative response within leaves by C.tricinctus.
Defence and development in a gregarious leaf‐mining beetle
Authors: DAMMAN HANS
Published: March 2008

Abstract.

The gregarious larvae of the chrysomelid beetle Microrhopala vittata mine the leaves of goldenrods (Solidago spp.). These mines serve both as food and as shelter for the larvae.

Life‐table data and experiments indicated that mine initiation and moves to secondary mines represented especially vulnerable stages during larval development. Leaf mines effectively protected M.vittata against predators in the field.

Field experiments indicated that larvae hatching from larger clutches of eggs stood a greater chance of surviving to pupation, primarily because larvae hatching in groups proved more successful at initiating leaf mines. Once inside the leaf mine, however, larvae feeding in large groups attained lower adult masses, and were more likely to abandon the natal mine and did so earlier in development because large groups more rapidly destroyed a leaf.
Root disturbance of common ash, Fraxinus excelsior (Oleaceae), leads to reduced foliar toughness and increased feeding by a folivorous weevil, Stereonychus fraxini (Coleoptera, Curculionidae)
Authors: FOGGO ANDREW , SPEIGHT MARTIN R. , GRÉGOIRE JEAN‐CLAUDE
Published: March 2008

Abstract.

Bioassays were carried out to examine differences in the feeding of a folivorous weevil, Stereonychus fraxini De Geer, on leaves from ash saplings with undamaged roots, and those with damaged roots. Beetles ate significantly more of the leaves of root‐damaged saplings in a choice experiment.

A separate study of the effect of root damage on leaf toughness was carried out on a second group of ash saplings. Saplings with damaged roots had less tough leaves than control saplings. Decreased leaf toughness in hypothesized as a mechanism to explain the preference of weevils for leaves from damaged trees.

Both chemical and physical changes may occur in the tissues of ash trees in response to environmental stress such as drought and root damage.

Root damage caused by agricultural disturbance is hypothesized as a mechanism making mature ash trees in hedgerow ecosystems more susceptible to insect herbivores.
Patch‐leaving rules for parasitoids with imperfect host discrimination
Authors: ROSENHEIM JAY A. , MANGEL MARC
Published: March 2008

Abstract.

The solitary parasitoid Anagrus delicatus attacks hosts (plant‐hopper eggs) that exist in distinct batches and that are readily detectable to the foraging parasitoid. However, Anagrus delicatus attacks only a small fraction of the available hosts within a batch of eggs and then disperses (Cronin & Strong, 1993a). Here we address the question: Why is A.delicatus abandoning seemingly high quality patches?

A parasitoid with an imperfect ability to discriminate between unparasitized hosts and hosts that it has attacked earlier within the same patch experiences a risk of self‐superparasitism when attacking multiple hosts within a single patch. Self‐superparasitism can incur costs in the form of lost time and eggs. Early patch leaving can be favoured as a means of avoiding the costs of self‐superparasitism.

A simple static model demonstrates that patch leaving is favoured by low costs of travelling to a new patch, high error rates in discriminating previously self‐parasitized hosts, and high levels of parasitism in the currently occupied patch.

A more detailed dynamic state variable model, parameterized for A.delicatus, demonstrates that this parasitoid's seemingly enigmatic behaviour can be explained under our hypothesis. In order for this to be the case, we predicted that A.delicatus cannot recognize previously parasitized hosts. Subsequent to our prediction, Cronin & Strong (1993b) demonstrated that experienced A.delicatus do not avoid ovipositing in previously self‐parasitized hosts.

Optimal patch leaving rules can be highly sensitive to even very low host discrimination error rates, which may be widespread among parasitoids.
Intraspecific variation in sperm precedence in the bruchid beetle Callosobruchus maculatus
Authors: EADY PAUL
Published: March 2008

Abstract.

By examining potential sources of intraspecific variation in sperm precedence, the underlying mechanisms of sperm competition in Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) were investigated.

The extent of sperm precedence was not related to either copulatory behaviour or body size (male and female).

The extent of sperm precedence increased during the egg‐laying period, suggesting that the stratification of sperm within the spermatheca is not the mechanism of sperm precedence.

Direct removal of sperm from the female's reproductive tract was not observed.

Four other mechanisms (not mutually exclusive) are proposed to account for last‐male sperm precedence in this species.
Forager polymorphism, size‐matching, and load delivery in the leaf‐cutting ant, Atta cephalotes
Authors: WETTERER JAMES K.
Published: March 2008

Abstract.

This study examined the importance of forager polymorphism and division of labour among foragers of different size for the economics of load delivery in a leaf‐cutting ant, Atta cephalotes (L.). I collected A.cephalotes foragers coming down trees carrying leaf fragments to evaluate the degree of match between forager mass and the density (mass per unit area) of leaves being cut, and to quantify how this match affects whether the mass of leaf fragments cut by the ants are within the range which maximizes the rate and efficiency of load delivery.

Foragers ranged 23‐fold in mass (1.4–32.1 mg). On average, larger workers cut at denser leaf sources. Leaf fragment area increased with ant mass, but relative area (fragment area/ant mass) decreased with ant mass. The density of a leaf type had little or no effect on the area cut by ants of a given size. As a result, ants of a given mass cut heavier fragments from the denser leaves. The effect of leaf density, however, was partly counteracted at the colony level by recruitment of larger ants, which cut smaller area fragments relative to their body mass, to cut at denser leaf sources.

Despite a fairly high variance in the relationship between ant mass and fragment mass, overall 87% of the laden ants (74–100% for different trees) carried leaf fragments in the 1.5–6 times body mass range. Earlier studies indicate that loads in this range yield the highest biomass transport rate and transport efficiency. Thus, the variance falls within bounds such that it has little effect on load transport efficiency. Having a broad range in optimal load mass may be considered an adaptation to the expected variability in load masses.

If there were no correlation between ant mass and leaf density, mismatches between ant mass and load mass would be more common than observed. Thus, size‐matching of larger workers to cut denser leaves increases the rate and ergonomic efficiency of load delivery.
Life history traits related to resource partitioning between synhospitalic species of Colocasiomyia (Diptera, Drosophilidae) breeding in inflorescences of Alocasia odora (Araceae)
Authors: YAFUSO MASAKO
Published: March 2008

Abstract.

Two closely related species of Colocasiomyia alocasiae (Okada) and C.xenalocasiae (Okada) (Diptera, Drosophilidae) breed in inflorescences of Alocasia odora C. Koch (Araceae), a hermaphroditic understorey clonal herb.

The two drosophilid species form a synhospitalic pair in Okinawa with alocasiae breeding in the upper half of the inflorescence and xenalocasiae breeding in the lower half.

C.alocasiae also has the following combination of life history traits: small body size, many eggs, and early reproductive maturity. In contrast, xenalocasiae can be described as having larger body size, fewer eggs, and delayed reproductive maturity.

Resource partitioning between the two species on the same host may be affected by these life history traits which are associated with their larval habitats.
Population structure in the small ermine moth Yponomeuta padelus: an estimate of male dispersal
Authors: BROOKES MARTIN I. , BUTLIN ROGER K.
Published: March 2008

Abstract.

An extensive investigation was carried out into the structure of a large, effectively continuous population of Yponomeuta padellus Latreille, feeding on hawthorn, Crataegus monogyna, and blackthorn, Prunus spinosa.

Mark—recapture studies were used to obtain direct estimates of the male dispersal rate, σ, in two successive years.

Dispersal was found to be extremely localized with respect to the total area of the study population. Estimates of u ranged from a minimum of 2.47 m to a maximum of 12.5 m.

Limited dispersal could be an important factor governing the genetic differentiation of Y.padellus populations, and its implications for the supposed existence of host races in this species are discussed.
Geographical and developmental components of adult size of neotropicalAnopheles(Nyssorhynchus)
Authors: LOUNIBOS L.P.
Published: March 2008

Abstract.

Wing lengths were used as indicators of size of host‐seeking females of four species of malaria vectors captured at human or animal baits in South America.

Geographic variation in size was observed among populations ofAnopheles aquasalisandA.nuneztovari, but notA.albitarsisorA.triannulatus.

The frequency distributions of wing lengths in large collections of host‐seekingA.aquasalisandA.albitarsisexhibited significant negative skewness, suggesting that the preponderance of biting females approached maximum size.

Relationships between season or physiological state (parity, blood, eggs) and the sizes of host‐seeking females were not generally significant.

WhenA.aquasalis, A.albitarsisandA.nuneztovariwere reared separately at two larval densities, initial density, but not species, significantly affected wing lengths. Significant species × density interactions may be attributable to species‐specific responses to density.

Compared to other mosquitoes, the sizes of host‐seekingAnopheles(Nyssorhynchus) varied little within natural populations. Laboratory studies on the fitness of unnaturally small malaria vectors may bear little relevance to the fitness of host‐seekingAnophelesin nature.
Predation and avoidance of tough leaves by aquatic larvae of the moth Parapoynx rugosalis (Lepidoptera: Pyralidae)
Authors: MUELLER ULRICH G. , DEARING M. DENISE
Published: March 2008

Abstract.

Aquatic larvae of the pyralid moth Parapoynx rugosalis Möschler repeatedly construct protective cases by cutting portions (discs) from leaves of the waterlily Nymphaea ampla and sandwich themselves between the disc and the underside of the host leaf. Construction of a new case requires leaving the old case, thus increasing exposure to predators and parasites.

In an experiment, larvae with protective cases experienced no mortality due to predation by fish, whereas larvae without cases experienced substantial predation.

In a series of choice tests, larvae preferentially selected young, tender leaves over old, tough leaves for construction of cases, and larvae spent significantly less time completing their shelters when cutting discs from young, tender leaves.

A partial explanation of why larvae select young, tender leaves for construction of their protective shelters may be that exposure time to predators during construction is minimized.

The same mechanism linking preferences for tender leaves to reduced exposure to predators during construction may also apply to other insect herbivores exhibiting leaf‐rolling or case‐building behaviour.
Seasonal and spatial population loads of a tropical insect: the case of the coffee leaf‐miner in Mexico
Authors: NESTEL DAVID , DICKSCHEN FRANZISCA , ALTIERI MIGUEL A.
Published: March 2008

Abstract.

The effect of weather fluctuations in a tropical rain forest upon a leaf‐miner (the coffee leaf‐miner Leucoptera coffeella Guerin‐Meneville (Lepidoptera: Lyonetiidae)) was studied in Veracruz, Mexico. The combined effect of temperature and precipitation upon the leaf‐miner populations was investigated in coffee plantations located along an elevation transect and throughout the annual seasons. The effect of plant diversity, displayed by the presence or absence of shade trees in coffee plantations, upon the population loads of the leaf‐miner was also investigated.

The leaf‐miner population increased significantly during the period of intermediate temperature and low precipitation (spring season). Elevation also affected the population load of the insect: leaf‐miner populations were larger at low elevations (where temperatures are high and precipitation low) than at high elevations.

Plant structural diversity did not affect the population loads of the leaf‐miner.

The results indicate that the direct and indirect effects of temperature and precipitation are significant factors in the population dynamics of the coffee leafminer. It is suggested that even moderate fluctuations in climatic conditions in tropical and subtropical regions may also play an important role in the dynamics of tropical insect populations, similar to that found in temperate zones where climatic fluctuations are extreme.