bluuebunny/crossref_metadata_2025 huggingface dataset:
Colonization, survival, and causes of mortality of Camerariu hamadryadella (Lepidoptera: Gracillariidae) on four species of host plants
Authors: CONNOR EDWARD F.
Published: March 2008

Abstract.

The abundance, survival, and causes of mortality of Cameraria hamadryadella (Clemens) (Lepidoptera: Gracillariidae) were examined on four host plant species in Virginia, U.S.A. Quercus alba L. and Q.rubra L. are native within the geographic range of C.hamadryadella, and Q.robur L. and Q.benderi Baenitz are exotic. Q.robur is native to Europe, North Africa, and Asia and was probably introduced prior to 1850, and Q.benderi is of hybrid origin and introduced to cultivation before 1900. Q.alba and Q.robur are in the subgenus Lepidobalanus (white oaks), and Q.rubra and Q.benderi are in the subgenus Erythrobalanus (red oaks).

Larval mines of C. hamadryadella were abundant on both white oak species, including the exotic Q.robur, but were rare on host plants in the red oak subgenus. Un‐hatched eggs of C.hamadryadella were not observed on red oaks. Other observations on host distribution indicate that C.hamadryadella is rarely found on red oaks. These observations are interpreted as circumstantial evidence that C. hamadryadella generally avoids ovipositing on red oaks.

Survival of C.hamadryadella to the adult stage was similar among all host species, but larvae tended to survive longer on hosts in the red oak subgenus. The observation of higher survival rates of early instar larvae on red oaks suggests that no nutritional or secondary chemical barrier reinforces the observed pattern of oviposition.

Significant differences in the distribution of the causes of mortality were detected between native and exotic host plant species. Larvae and pupae on native hosts were more likely to die because of predation, while those on exotic host plants were more likely to die because of parasitism and host feeding by adult female parasitoids. This pattern could arise because parasitoids prefer to forage on exotic host plants or because predators avoid foraging on exotic plants.

This study shows for C. hamadryadella that the only barriers to colonization and use of exotic hosts, in the white and red oak subgenera, are the presence of cues sufficient to stimulate oviposition and/or the absence of cues to deter oviposition. It also suggests that the presence of closely related native host plants in the region of introduction will increase the probability that exotic plants will be colonized by phytophagous insects.
Changes in feeding habit as caterpillars grow
Authors: GASTON KEVIN J. , REAVEY DUNCAN , VALLADARES GRACIELA R.
Published: March 2008

Abstract.

200 of 1137 species of British microlepidoptera make a single marked change in feeding habit as they grow.

Most numerous are species that change from leaf mining to one of case bearing, spinning, tying and rolling or concealed feeding, and species that change from concealed feeding to case bearing or spinning, tying and rolling.

Although in some instances numbers of closely related species make similar changes in behaviour, most changes observed are scattered among subfamilies.

Leaf miners have considerably smaller adults than concealed feeders, which themselves are smaller than external feeders and spinners, tiers and rollers. When case bearers are excluded from the analyses, species that remain as leaf miners or concealed feeders throughout larval development are on average smaller as adults than those that start out with these feeding habits but later change.

We suggest a number of reasons why larvae might make such fundamental switches.
Egg size increases with maternal age in the cotton stainer bugs Dysdercus fasciatus and D.cardinalis (Hemiptera: Pyrrhocoridae)
Authors: KASULE F. K.
Published: March 2008

Abstract.

Egg‐size variation over the reproductive span of laboratory‐reared females is described in two species of cotton stainers: Dysdercus fasciatus Sign. from woody Malvales and D.cardinalis Gerst. from herbaceous Malvales.

Egg size increases with maternal age due to a decrease in clutch size as maternal age advances in both species.

The two species are similar in size, but egg size is about 28% larger and clutch size about 19% smaller in D.fasciatus than in D.cardinalis. These contrasts may be related to the host‐plant biology which differs between the two species.
The influence of habitat use and foraging on the replacement of one introduced wasp species by another in New Zealand
Authors: HARRIS R. J. , THOMAS C. D. , MOLLER H.
Published: March 2008

Abstract.

New Zealand was colonized by the German wasp, Vespula germanica (F.), in the 1940s and it subsequently became established throughout the country. The common wasp, V.vulgaris (L), colonized in the late 1970s and is still spreading.

The common wasp has replaced the German wasp in some habitats in New Zealand. Samples from a nationwide postal survey indicate that the common wasp is now the more abundant species in honeydew beech forests (Nothofagus spp.), and to a lesser extent in other native forests. The German wasp is still the more abundant wasp in rural areas (excluding forest). The two species are at present co‐dominant in urban areas, although this may be a transient phase.

In honeydew beech forest the two species show different foraging patterns that provide the potential for local coexistence. Although both species are generalist feeders, the German wasp is more commonly found foraging for protein amongst the forest litter, whereas the common wasp forages more on shrubs and tree saplings. Despite this difference, the common wasp can still replace the German wasp in honeydew beech forest within a few years of invasion.

In honeydew beech forests in which the German wasp is the more abundant species it dominates honeydew trunks (sugar resource), whereas the common wasp dominates honeydew trunks in areas where it is the more abundant species. The change from German to common wasp domination of honeydew trunks is more rapid than the change in dominance in other microhabitats. Aggressive interactions may be taking place on this high quality, potentially defensible sugar resource.
Characteristics of dispersal in sexually mature dragonflies
Authors: MICHIELS N. K. , DHONDT A. A.
Published: March 2008

Abstract.

The population dynamics of a natural population of Sympetrum danae (Sulzer) were studied, by means of a mark—release—recapture method, to find indications of dispersal by mature adults. Additional information on orientation and the influence of phenotype (including age), density and weather was obtained by observations under natural conditions and in a large outdoor field cage.

80% of all mature adults caught around the natural pond were estimated to be immigrants. Considerable immigration was confirmed by the abdomen length of unmarked matures which did not accord with that expected from the locally emerged population. Total numbers captured and the minimum number known to be alive fell sharply at the time when most individuals were mature. At the same time, new matures continued to enter and disappear from the study area at an increasing rate.

Dispersive behaviour (escape flights) in the field enclosure was primarily age dependent in both sexes: it occurred from an age of 25–30 days onwards. This coincides with the time‐lag between the emergence peak and increased dispersal in the field. Secondary effects on escape flights suggested that males tended to abandon low density areas.

Males flew relatively more southward than females.
Mating system of Bracon hebetor (Hymenoptera: Braconidae)
Authors: ANTOLIN M. F. , STRAND M. R.
Published: March 2008

Abstract.

We report on the mating system of a field population of the parasitic wasp, Bracon hebetor, on a corn pile infested by the Indian meal moth, Plodia interpunctella. We demonstrate that the mating system is based upon male scramble competition polygyny with male aggregations on high places on the corn.

The sex ratio among adults was greater than 80% males on the surface of the corn, whereas below the surface the sex ratio was less than 45%. Males actively courted females on the surface, but there were no aggressive interactions among males during courtship or mating.

Approximately 20% of the females found on the surface of the corn had no sperm in their spermathecae, regardless of age, but the numbers of unmated females decreased later during the day.

In laboratory studies we showed that females from this population oviposit a female biassed sex ratio, and that only 14% of females were mated before dispersing from their place of emergence.

Thus sib‐mating is unlikely in this gregarious parasitoid. This outcrossing mating system probably arose because of severe inbreeding depression that B.hebetor suffers via a sex locus: diploids that are heterozygous at the sex locus develop into females, but homozygous diploids are male and are generally inviable. The female biassed sex ratio may have evolved in B. hebetor in response to males being the more expensive sex, females dispersing more frequently from the population than males, or a fraction of females remaining unmated in the population.
Life cycle and food availability indices in Notiophilus biguttatus (Coleoptera, Carabidae)
Authors: ERNSTING G. , ISAAKS J. A. , BERG M. P.
Published: March 2008

Abstract.

Food demands of the predatory carabid Notiophilus biguttatus F. and their fulfilment were studied in the laboratory and field.

In the laboratory, larval consumption, growth, adult body size and egg production were established for different regimes of temperature and food, the springtail Orchesella cincta.

Temperature strongly influenced feeding rate of larvae and adults and consequently growth and oviposition rates. Accordingly, growth rate and ovi‐position rate increased with prey supply.

Prey supply also had an effect on fat content, but the number of ripe eggs in the ovaries was related neither to temperature nor to prey supply.

Adult body size was affected by temperature during the larval period but more so by food supply.

Dissection of field fresh females showed them to bear eggs for the whole year, except in late winter/early spring and in July.

Fat content was low in spring and, from July on, high in summer and autumn. Survivorship during starvation differed widely between samples and seemed to be related to reproductive status rather than to fat content.

Samples of beetles and springtails from eleven pine plantations revealed for the beetles significant differences in fat content and body size, the latter ranging between the maximum and minimum value obtained in the laboratory.

Conclusions about food limitation based on body size and fat content were not corroborated by a relationship of these indices with springtail density.
Taking a chance on moths: oviposition by Delia flavifrons (Diptera: Anthomyiidae) on the flowers of bladder campion, Silene vulgaris (Caryophyllaceae)
Authors: PETTERSSON MATS W.
Published: March 2008

Abstract.

Delia flavifrons Zetterstedt (Diptera: Anthomyiidae) visits flowers of Silene vulgaris (Moench) Garcke (Caryophyllaceae), where the adults feed, mate, lay their eggs, and the larvae feed on developing seeds. The objective of the study was to examine how an ovipositing female fly assures a food resource for her progeny.

Ovipositing females preferred young, non‐pollinated flowers over older pollinated ones. The flies did not pollinate the flowers and survival of the larvae depended on the flowers being pollinated by moths.

Flowers containing fly eggs were pollinated more often than expected from chance, probably as a result of both flies and moths visiting particular flowers.

Eggs were laid singly, and multiple oviposition occurred randomly. Although most eggs hatched, only about half produced larvae that made their way into the fruits. As a result, the probability of competition arising from multiple oviposition may be reduced to such an extent that selection does not favour females that avoid flowers with conspecific eggs.

Moth larvae of the noctuid genus Hadena also feed on the seed pods of S. vulgaris and will kill any fly larvae they encounter. However, there was no deviation from random oviposition by the flies in relation to eggs laid by the moths, but the competitively weaker fly usually started to lay eggs towards the end of the moth's egg‐laying period.

The relationship between Delia flavifrons and Silene vulgaris superficially parallels that for known pollinator/predator systems, but floral adaptations to hypothetically pollinating flies seems not to have taken place.
Host plant dispersion, leaf hopper movement and disease transmission
Authors: POWER ALISON G.
Published: March 2008

Abstract.

The plant‐to‐plant movement of the corn leafhopper, Dalbulus maidis Delong & Wolcott, and the spread of the leafhopper‐borne maize rayado fino virus were investigated in four patterns of maize (Zea mays) dispersion.

D. maidis was less abundant and the spread of the virus was slower in dense stands of maize than in sparse stands.

When plant density was held constant, leafhoppers were more abundant in maize stands with relatively equidistant plant spacing (uniform dispersion) than in stands with densely‐sown rows (linear dispersion) or double‐sown hills (clumped dispersion), but there was no difference in virus incidence among these plant dispersion patterns.

Leafhoppers were less likely to move to adjacent plants in uniform plant dispersion patterns than in either linear or clumped dispersion patterns. This result may explain the lack of higher virus incidence in uniform stands, despite higher leafhopper abundance.

Leafhopper movement was consistent with a simple rule: the shorter the distance to the next adjacent plant, the more likely a leafhopper is to move between plants.

These results demonstrate that host plant dispersion can affect the abundance and behaviour of highly mobile herbivorous insects even when plant density is constant.
The role of sugars in western spruce budworm nutritional ecology
Authors: CLANCY KAREN M.
Published: March 2008

Abstract.

The western spruce budworm, Choristoneura occidentalis Freeman, and Douglas‐fir, Pseudotsuga menziesii (Mirb.) Franco, have been used to test the hypothesis that variation in levels of foliar sugars form part of the basis for plant resistance to herbivore attack.

Budworm population growth was evaluated on artificial diets with 2–45% sucrose using a three generation bioassay. Diets with 1.2% and 3.9% N were tested to determine if responses to sugar were dependent on levels of protein. The 3.9% N diets were supplemented with a mineral salt mixture, so they had high levels of N and minerals.

The response of budworm population growth to sucrose concentrations ≤20% was convex at 1.2% N and flat for 3.9% N. Population growth on the 1.2% N diet, which had levels of N and minerals similar to host foliage, was good with only 2% sugar, but optimal at the 6% sucrose level; the number of F1, F2 and F3 larvae produced declined substantially when sugar was increased to 11% and 20%. On the 3.9% N diets, population growth was equivalent for diets with 2% and 11% sucrose. Sucrose concentrations ≥29% were detrimental to the budworm at both N levels.

Sugar concentrations in Douglas‐fir foliage varied between 5.7% and 18.4%. Thus, results from the 1.2% N experiment indicated that budworm performance was best on diets with sugar concentrations near the lower limit observed for host foliage. This implies that plants with higher foliar sugar may be inferior hosts for the budworm. Field observations supported this conclusion, as putatively resistant Douglas‐fir trees had significantly higher levels of sugars in their foliage than nearby paired susceptible trees. Variation in foliar sugars among individual trees may be part of the mechanism in Douglas‐fir resistance to C.occidentalis damage.
Guild structure in solitary spider‐hunting wasps (Hymenoptera: Pompilidae) compared with null model predictions
Authors: FIELD JEREMY
Published: March 2008

Abstract.

Three aspects of prey utilization are documented in a guild of spider‐hunting pompilid wasps at a Breckland heath site: female phenology, size, and microhabitat utilization.

Twenty‐four species were present at the site, 59% of the British fauna. Ten species individually represented more than 1% of the guild.

Pompilid abundance peaked in early July and mid‐late August. Anoplius viaticus had a different life‐history from other common guild members, making its inclusion in the guild questionable.

Most species represented by large samples occurred in all microhabitats and time intervals, and all species overlapped in size with all other species except A. viaticus. Arachnospila anceps was numerically dominant in all microhabitats and most time intervals.

Mean pair‐wise overlaps in phenology and microhabitat utilization were significantly lower than predicted by null models, consistent with the idea that interspecific competition has been important in determining guild structure.

Female size is highly correlated with prey size, but the distribution of mean female sizes did not generally differ from null expectations.

Interpretation of comparisons with null models is problematic, particularly because it is difficult to quantify evolutionary ‘favourability’ of different resource states. Null models are currently of limited use because the patterns expected to result from key processes such as competition are uncertain in multi‐dimensional systems.
Egg cannibalism by larvae and adults of the milkweed leaf beetle (Labidomera clivicollis, Coleoptera: Chrysomelidae)
Authors: DICKINSON JANIS L.
Published: March 2008

Abstract.

Egg cannibalism is a form of infanticide that has been implicated in the evolution of guarding of eggs and immatures in some species of insects. The milkweed leaf beetle, Labidomera clivicollis (Coleoptera: Chrysomelidae), exhibits three types of egg cannibalism in the field: siblicide, cannibalism of eggs by older larvae from earlier hatching egg clutches, and cannibalism of eggs by adult females. Unlike their close relative, L.suterella (Choe, 1989), female L.clivicollis do not guard their eggs or immatures. They move slowly about a patch of milkweeds laying multiple egg clutches.

First instar and older larvae cannibalized eggs in two geographically separated study populations (subspecies) in Austin, Texas, and Bridgeport, New York, U.S.A. Although adult females of both populations cannibalized eggs in the laboratory, only the Texas subspecies, L.c.rogersii, exhibited such cannibalism in the field.

In the field, correlates of siblicide varied both temporally (within subspecies) and spatially (between subspecies) in terms of whether they were statistically significant, but trends were all in the same direction. Group size was positively correlated with hatching success and siblicide, but negatively correlated with other types of predation. Siblicide was also positively correlated with egg density in a laboratory study of the Texas subspecies, L.c.rogersii.

In the laboratory, an average of 15–17% of L.c.clivicollis eggs never developed embryos. Although these were almost always cannibalized, some viable eggs were also eaten and there is no evidence that females increased the proportion of infertile eggs they laid to increase siblicide.

Field data and laboratory experiments showed that adult female L. c.rogersii cannibalized eggs while males rarely did. Females preferentially ate the eggs of other females over their own eggs in an experiment that removed spatial cues.

Although the selective context of cannibalism is not demonstrated here, I suggest that females may increase siblicide by increasing egg density and may cannibalize eggs to protect their own eggs from being eaten by second and third instar larvae produced by other females.
Interference competition in ant‐lion (Macroleon quinquemaculatus) larvae
Authors: GRIFFITHS DAVID
Published: March 2008

Abstract.

The effects of density, feeding regime, and body size on interference competition in the pit‐digging larvae of the ant‐lion Macroleon quinquemaculatus (Hagen) were investigated in laboratory experiments.

Competition had little effect on the pit size of winners but losers constructed much smaller pits than isolated larvae. Losers were less likely to dig or maintain pits and more likely to move than winners.

Competition was much stronger between well‐fed larvae than between hungry ones, and well‐fed competitors showed reduced growth rates. Well‐fed larvae orientated themselves so that they could throw sand into their neighbour's pit whereas hungry larvae faced away from each other. Differences in hunger level reversed the competitive advantage of larger larvae only when individuals were of similar size.

Cannibalism was density‐dependent and most frequent in hungry, similar‐sized, larvae; the smaller larva was usually the victim.

Displays/challenges between larvae affected the distance between pits. Body size was the main determinant of contest outcome though pit ownership and hunger level also had an effect.
Asymmetric larval competition between two species of solitary parasitoid wasps: the influence of superparasitism
Authors: MACKAUER M. , BAI B. , CHOW A. , DANYK T.
Published: March 2008

Abstract.

We test the hypothesis that a solitary parasitoid wasp may gain in fitness if she lays more eggs in a host.

Using heterospecific superparasitism (=multiparasitism) between the solitary aphid parasitoids, Aphidius smithi Sharma & Subba Rao and Ephedrus californicus Baker, we show that (i) a superparasitizing female's chance that her offspring will survive competition is an increasing function of egg density, and (ii) survival among same‐aged larvae is independent of the oviposition sequence.

These findings on asymmetric larval competition provide indirect evidence that supports two fundamental, but untested, assumptions underlying models of adaptive superparasitism between conspecific wasps.
Influence of egg load and host size on host‐feeding behaviour of the parasitoid Aphytis lingnanensis
Authors: ROSENHEIM JAY A. , ROSEN DAVID
Published: March 2008

Abstract.

Direct behavioural assays were used to investigate the influences of host size and parasitoid egg load on the decision to host feed versus oviposit made by the parasitoid Aphytis lingnanensis Compere. Egg load was manipulated without concurrent influences on the history of host contact by exploiting size‐related variation in fecundity and by holding parasitoids at different temperatures to vary the rate of oocyte maturation.

Host feeding comprised a series of feeding bouts, separated by renewed probing of the scale insect body. Successive feeding bouts were progressively shorter, suggesting that hosts represent ‘patches’ yielding resources at a decelerating rate.

Parasitoids were significantly more likely to host feed on smaller hosts and oviposit on larger hosts.

Neither egg load nor the treatment variables (parasitoid size and holding temperature) exerted significant influences on the decision to host feed versus oviposit on second instar (low quality) hosts.

The failure to observe an effect of egg load on host‐feeding decisions was not simply a reflection of the parasitoids being entirely insensitive to egg load; significant effects of egg load on parasitoid search intensity and clutch size decisions were observed.

Parasitoids developing on second instar (low quality) hosts experienced high levels of mortality late during development and yielded very small adults.

The discord between these experimental results and predictions regarding the importance of egg load underscores the need for additional work on the proximate basis for host‐feeding decisions and the nutritional ecology of insect parasitoids.
Laboratory study of cannibalism and interspecific predation in ladybirds
Authors: AGARWALA B. K. , DIXON A. F. G.
Published: March 2008

Abstract.

In the absence of aphids, adult females of Adalia bipunctata (L.) showed a greater reluctance to eat eggs than males.

Eggs and young larvae were more vulnerable to cannibalism than older larvae and starved larvae were more vulnerable than well‐fed larvae.

Both egg and larval cannibalism is inversely related to the abundance of aphids.

Eggs are a better food, in terms of larval growth and survival, than aphids.

In the absence of aphids interspecific predation occurred, but not equally, between the coccinellids A.bipunctata, A.decempunctata (L.), Coccinella septempunctata L. and C.undecempunctata L.

Larvae and adults of A. bipunctata and C.septempunctata were reluctant to eat conspecific eggs painted with a water extract of the other species' eggs and larvae of C. septempunctata were more likely to die after eating a few eggs of A.bipunctata than vice versa.

These results indicate that cannibalism occurs mainly when aphid prey is scarce and is adaptive in that it improves the chances of survival, and coccinellids, to varying degrees, are defended against interspecific predation.
The occurrence and effect of a protozoan parasite, Ophryocystis elektroscirrha (Neogregarinida: Ophryocystidae) on overwintering monarch butterflies, Danaus plexippus (Lepidoptera: Danaidae) from two California winter sites
Authors: LEONG K. L. H. , KAYA H. K. , YOSHIMURA M. A. , FREY D. F.
Published: March 2008

Abstract.

Monarch butterflies, Danaus plexippus, from two overwintering populations, were found to have Ophryocystis elektroscirrha spores on their scales at rates between 53% and 68%. The frequency of butterflies with O.elektroscirrha spores remained about the same between sites and throughout the winter.

The spores, recovered from all parts of the body of the butterfly, were most numerous on the abdomen, particularly near the posterior third.

Butterflies with spores survived as long as those without detectable spores at 10.1°C ±0.4 SE and 78.3% r.h. ±0.6SE. Insects with spores held at 19.4°C ±0.4SE and 44.9% r.h. ±1.5SE showed a significantly higher rate of moisture loss and survived a shorter period than monarch butterflies without detectable spores.
The significance of host patch edges to the colonization and development of Corythucha marmorata (Hemiptera: Tingidae)
Authors: CAPPUCCINO NAOMI , ROOT RICHARD B.
Published: March 2008

Abstract. 1. Corythucha marmorata (Hemiptera: Tingidae) was more abundant in clusters of small experimental patches of its host plant, goldenrod (Solidago altissima), than in large patches covering the same area.

2. Adults and egg masses were more abundant on stems on the edges of the patches than on those in the interior.

3. Female Cmarmorata caged on edge plants laid more eggs than females caged on interior plants, and eggs on exposed plants developed faster than those in the middle of a pacth.

4. A preference for edges results in negative ‘response’ to patch size because large patches invariably have a lower proportion of edge than small patches.
The allocation of foragers in red wood ants
Authors: GORDON DEBORAH M. , ROSENGREN RAINER , SUNDSTRÖM LISELOTTE
Published: March 2008

Abstract. 1. We studied how colonies of the red wood ant, Formica polyctena, adjust the numbers of foragers allocated to different foraging trails. In a series of field experiments, foragers were marked and transferred from one nest to another, related nest, where they joined the foraging force. Transferred workers acted as a reserve of uncommitted, available foragers.

2. Previous work shows that each individual forager habitually uses one trail. We found that for an uncommitted forager, the influence of recruitment initially is stronger than that of directional fidelity. Transferred workers were likely to use trails leading to new food sources. When transferred to a new nest, foragers were not likely to use a trail in the same direction as their original trail in the donor nest.

3. After a week, transferred foragers tended to develop route fidelity. Even after bait was no longer present, they continued to use the trail that had formerly led to a bait source.

4. We examined how colonies adjust numbers on a trail by experimentally depleting some trails. Colonies usually did not compensate for depletion: foragers were not recruited to depleted trails.

5. In general, the dynamics of foraging in this species facilitate a consistent foraging effort rather than rapid adjustments of forager allocation.
Food level reaction norms in size‐selected milkweed bugs (Oncopeltus fasciatus)
Authors: DINGLE HUGH
Published: March 2008

Abstract. 1. The hypothesis that the small size of nonmigratory milkweed bugs from Puerto Rico (relative to large migratory bugs from Iowa) might be an adaptation to low food levels was tested with bugs selected for large and small size as the consequence of positive genetic correlation between body size and wing length. The test involved examining reaction norms of life history traits to different food levels.

2. When nymphs were reared on 3 milkweed seeds per nymph from hatch to adult eclosion, large bugs were adversely affected with only 50% and 60% in each of two replicates reaching adulthood. Control (unselected) and small bugs, however, were unaffected at this food level. None of the lines was affected at levels of 6 and 12 seeds per nymph.

3. When adults were reared from eclosion on 12, 18 or 24 milkweed seeds per bug, large bugs were adversely affected relative to control and small bugs at all three food levels. At each food level fewer large bugs produced eggs than either small or control bugs which did not differ.

4. The evidence from the food level reaction norms suggests that larger bugs will be selected against during periods of food shortage of the sort likely to occur in Puerto Rico.
Population dynamics of Siphoninus philyreae in California in the presence and absence of a parasitoid, Encarsia partenopea
Authors: GOULD JULI R. , BELLOWS THOMAS S. , PAINE TIMOTHY D.
Published: March 2008

Abstract. 1. Densities of the whitefly, Siphoninus phillyreae Haliday, remained at low levels at two sites where a parasitoid, Encarsia parknopea (Walker), was released on whitefly‐infested ash, Fraxinus sp., and pomegranate, Punica granatum. Populations of S.phillyreae at control sites, where parasitoids were absent, were increasing in density at the beginning of the summer.

2. By mid‐summer, E.partenopea had appeared at all four control sites, and densities of S.phillyreae declined to levels similar to those at the release sites.

3. In the absence of the parasitoid, the age structure of S.phillyreae populations was dominated by the egg stage, indicating a population increasing in density. After E.partenopea became abundant at a site, the age structure of the population had a decreasing proportion of young stages.

4. The changes in S.phillyreae age structures were explained by examining the percentage of fourth instar S.phillyreae from which E.partenopea, as opposed to adult whiteflies, emerged. After the parasitoid became abundant at a site, the majority of fourth instars produced parasitoids rather than whitefly adults. The result was that the adult S.phillyreae population declined, and few eggs were laid.

5. The dynamics of the interaction between E.partenopea and S.phillyreae were similar on ash and pomegranate.
The influence of temperature on nest site choice and reproductive strategy in a temperate zone Polistes wasp
Authors: JEANNE ROBERT L. , MORGAN RANDY C.
Published: March 2008

Abstract. 1. Field experiments with Polistes fuscutus showed that more nests were initiated, co‐foundress groups were larger, broods developed faster, and workers eclosed earlier in sun‐warmed sites than in cool ones.

2. These results suggest that colonies nesting in sun‐warmed shelters gained a fitness advantage over those in cooler shelters. More rapid brood development means that such colonies reach the ergonomic stage more quickly, which in turn means a higher expectancy of survival and greater productivity at the end of the season.

3. We argue that thermal properties constitute an important component of Polistes nest site quality in temperate regions and that these properties influence joining and usurping strategies as well as nest site choice in spring Polistes females. Other factors being equal, a joining or usurping female should opt for a colony in a warm site over one in a cool site, leading to the larger foundress groups we found in warm shelters.

4. We hypothesize that the selective advantage of philopatry in temperate zone Polistes populations is that it brings spring females to nest sites of proven quality.
Family structured patterns of mortality in the false Colorado potato beetle
Authors: McCAULEY DAVID E.
Published: March 2008

Abstract.1. The distribution of mortality within and among groups of immatureLeptinotursu juncta(Germar) (Coleoptera: Chrysomelidae) was studied in the field at three points in the life‐cycle in order to test whether the fates of individuals occupying the same host plant were non‐independent.

2. Studies were conducted on eggs subject to cannibalism and predation, on newly hatched larvae subject to predation, and on older larvae subject to parasitism byMyiophurus doryphorue(Riley), a tachinid fly.

3. At all three points in the life‐cycle the variance in group‐specific survivorship rates was demonstrated to be significantly greater than expected when individual deaths are distributed randomly among groups, with standardized variances ranging from 42% to 52% of the maximum possible.

4. A statistically significant positive correlation was shown between the number of individuals in a group and the group‐specific survivorship rate at all three life stages.

5. The distribution of genetic variants within and among groups of larvae showed the groups to be mixtures of full and half siblings, with an average coefficient of genetic relatedness,r, equal to 0.38.
Daily biphasic behaviour in keratin‐feeding desert trogid beetles in relation to climate
Authors: SCHOLTZ C. H. , CAVENEY S.
Published: March 2008

Abstract. 1. Patterns of daily activity of two ectothermic species of the trogid genus Omorgus were studied in the Kalahari of southern Africa in summer. The relationship between time and type of activity, and environmental temperature, relative humidity and light intensity, was investigated.

2. Beetle activity was biphasic, with peaks in activity at sunset and sunrise in both species.

3. Afternoon activity coincided with high temperatures and low humidity and morning activity with minimum daily temperature and maximum humidity.

4. Afternoon activity, which peaked at about 34°C and 25% r.h., consisted predominantly of complex breeding behaviour and dispersal. High temperatures are necessary for these activities.

5. In the morning feeding predominated. At this time temperature was about 27°C and r.h. above 60%. High r.h. is important because it restricts respiratory loss of water, improves food (moist hair and skin keratin) quality and may compensate for faecal water loss.

6. No evidence of competition between the two species was found.
Sex ratio and maternal investment in the multivoltine large carpenter bee Xylocopa sulcatipes (Apoideh: Anthophoridae)
Authors: STARK ROLAND E.
Published: March 2008

Abstract. 1. Females of the multivoltine carpenter bee Xylocopa sulcutipes (Maa) (Hymenoptera: Anthophoridae) usually excavate a straight tunnel in dead twigs and mass provision a linear array of up to ten brood cells with pollen and nectar. An egg is deposited upon each food mass within one cell.

2. Female offspring generally receive a higher provisioning mass (0.180 ± 0.048 g) than males, a significant difference (P > 0.001). There are, however, male larvae that receive as much food or more as their sisters or female larvae reared in another nest.

3. There is a close positive association between the size of a mother and the weight of provisions for individual daughters, but not for sons.

4. Female offspring are positioned in the innermost brood cells (Gositions 1, 2 and 3). The sex ratio of the outer cells is either significantly male biased (positions 4–6) or skewed towards males (positions 8 and 9). Positions 7 and 10 are in equilibrium.

5. Solitary females produce a significantly female biased sex ratio (P < 0.01). Sex ratio in social nests is skewed toward females, but not significantly so (P < 0.2). There is no significant difference between the sex ratio of solitary and social nests (P= 0.361). The population sex ratio (pooled sex ratio of all broods produced) is significantly female biased (P= 0.003).

6. Females kept in the laboratory produced female biased sex ratios whilst unmated females produced all‐male broods indicating that insemination and ovarian development are not causally related.

7. The expected sex ratio (ESR) under equal investment, calculated as 1/CR (CR = mean male provision weight/mean female provision weight), is 137.5:117.5 (males:females), and differs significantly from that observed, 104:151 (males:females) (P < 0.001). The ‘Local Resource Enhlancement’ hypothesis best explains the female biased sex ratio found in X.sulcatipes and its maintenance in the population.
Leaf miner assemblies: effects of plant succession and grazing management
Authors: STERLING P. H. , GIBSON C. W. D. , BROWN V. K.
Published: March 2008

Abstract. 1. Changes in leaf‐miner assemblies during 4 years of secondary succession, under different controlled sheep‐grazing treatments, are described and compared to the miner fauna of older grazed grassland nearby.

2. Multivariate analyses were used in conjunction with examination of individual common species to assess the independent effects of time, grazing treatment, plant species composition and architecture on the leaf‐miner assemblies.

3. Leaf‐miner species composition was strongly related to plant species composition, but was modified by plant structure under different grazing treatments. There was a strong successional trend in miner assemblies, even when the effects of changes in plant composition had been taken into account. Conversely, local variation in miner species composition generally reflected foodplant distribution alone.

4. Grazed treatments had fewer mines than controls, but there were also species specializing in grazed areas, despite the abundance of their foodplants elsewhere. There was a weak indication that miner species in grazed treatments were more likely to fluctuate in abundance than those in controls.

5. The results are discussed in relation to the assembly of grassland insect communities during succession, and the use of ‘indicator groups’ in management for nature conservation.
The effects of male body size on territorial and mating success in the landmark‐defending fly Hermetia comstocki (Stratiomyidae)
Authors: ALCOCK JOHN
Published: March 2008

Abstract.

Males of Hermetia comstocki Williston compete for territorial control of certain agaves and yuccas. Winners copulate with females that visit these plants solely to acquire a mate.

Males vary in body weight by more than an order of magnitude and larger flies almost always defeat smaller ones in aerial contests for control of landmark territories.

The mean body size (as measured by wing‐length) was significantly greater for males retaining residency at a site for at least one hour compared to males unable to do so. Likewise, males able to return to a perch site in the study area on more than one day were larger on average than males unable to do so.

Male preferences for landmark territories remained similar across years. Large males dominated the perch landmarks most likely to be occupied by males and most likely to be visited by females.

Despite the fighting and territorial advantages enjoyed by large males, the mean size of males found mating with females was not significantly larger than that of the general population.

The apparent failure of large males to secure a statistically significant mating advantage may be a statistical consequence of the small sample size of males observed mating. On the other hand, any mating advantage of large males may be reduced because (a) receptive females visit many different landmarks, (b) females mate with the first male they encounter at a landmark, regardless of his size, (c) there are usually many vacant landmarks available for smaller males, and (d) even popular territories are often open to small males, thanks to the low site‐tenacity of territory owners.
Temperature and the pollinating activity of social bees
Authors: CORBET SARAH A. , FUSSELL M. , AKE R. , FRASER A. , GUNSON C. , SAVAGE A. , SMITH K.
Published: March 2008

Abstract.

Thermal constraints on flight acivity limit the pollinating effectiveness of bees. Each species of social bee has a microclimatic ‘window’ within which foraging flight can be sustained.

To predict whether a given species of social bee is worth testing as a pollinator in a given climate, it is useful to know at least the lower limits of that microclimatic ‘window’. We consider how information from a series of bee counts through a day can be used to characterize a bee species in terms of activity/microclimate relations as a basis for predicting the diel pattern of foraging activity of a bee introduced into a new climate as a pollinator.

We discuss the relative merits of bee counts at a foraging patch and counts based on hive traffic as indices of the proportion of bees active.

We suggest that the activity/microclimate relations of a species be expressed in terms of the lower threshold black globe temperature for flight activity. Black globe temperature, Tg, is easily measured with inexpensive equipment, and can substitute for measurements of ambient temperature and radiation as a predictor of diel patterns of bee activity.

We use examples of field data to explore the relationship between microclimate and activity for the honeybee Apis mellifera and several species of bumblebee, Bombus. Regression analysis is used to relate activity to Tg and to identify the lower temperature threshold for activity from field bee counts.

In field studies analysed here, the bumblebees Bombus terrestrisllucorum, B.pascuorum and B.hortorum began foraging at lower temperatures than honey‐bees or B.lapidarius.
Social structure in the ant Lasius flavus: multi‐queen nests or multi‐nest mounds?
Authors: BOOMSMA J. J. , WRIGHT P. J. , BROUWER A. H.
Published: March 2008

Abstract.

The yellow subterranean ant Lasius flavus is generally considered to have a single queen in mature nests. Yet, many anecdotal observations have suggested that the conspicuous earth mounds of this ant may, at least occasionally, contain several queens and their offspring.

To estimate the number of matrilines per mound, samples for horizontal starch gel electrophoresis were collected from a total of thirty‐seven mounds in three sites of old chalk‐grassland in southern England.

Allozymatic variation at an esterase and hexokinase locus showed that probably more than 50% of the mounds contained more than one queen and that the mean number of queens per mound is at least 1.5–2.

Further results strongly suggested that workers from different matrilines may share the same galleries, at least in the top of the mound.

The apparently variable social structure of Lasius flavus colonies is discussed, both technically and with reference to ecological processes related to the presence of ants in the nest mounds.
Female‐biased sex ratio in a wild bruchid seed‐predator, Kytorhinus sharpianus. I. Larval competition and other factors
Authors: ISHIHARA MICHIHIRO , SHIMADA MASAKAZU
Published: March 2008

Abstract.

A wild bruchid seed‐predator, Kytorhinus sharpianus, has a complex life cycle consisting of bi‐ and trivoltinism on a wild leguminous plant, Sophola flavescens. Observations of adults showed significant female‐biased sex ratios (from 1:2 to 1:6) for nine generations over 4 years.

To investigate the potential effects of larval competition on the sex ratio, we altered the number of hatched eggs per seed and counted emergent males and females under laboratory conditions. Although only one adult could emerge per seed, the ratio of the females that emerged increased with the number of hatched eggs per seed. However, the sex ratio was not significantly different from 1:1 in the case of one hatched egg per seed.

We dissected seeds bearing two hatched eggs at regular intervals, and classified the surviving and the dead larvae according to their developmental stage. Over time, one larva within each seed always survived, while the other larva died from the second to fourth instar before the seed resource became exhausted.

In order to study the effects of the difference in the stages of two larvae in a seed on the emergence sex ratio, we manipulated intervals between the first and second ovipositions in the laboratory. As the difference in developmental stages of the two larvae increased, the closer to 1:1 the emergence sex ratio became.

Field observations, however, showed that about 60% of infested seeds were bored by only one K.sharpianus larva. This suggests that female dominance in larval competition within a seed may be relatively unimportant in causing the female‐biased sex ratio in the field.
Windborne moth migration over the Middle East
Authors: PEDGLEY D. E. , YATHOM S.
Published: March 2008

Abstract.

From 10 years' records of moths caught in a light trap at Eilat, Israel, eleven selected occasions with sudden increases in catch involving seventeen species were related to accompanying changes in wind.

At all times of the year examined, sudden increases in catch of all species were associated with winds changing direction to blow from the Nile Delta or from the Levant.

All seventeen species are inferred to be windborne over at least several hundred kilometres.

The results are consistent with huge plumes of moths streaming downwind each night from the Delta and the Levant, sometimes crossing Eilat, sometimes crossing the Mediterranean, but more often passing into the deserts.

Plumes are produced throughout the breeding season of each species.

The results are probably representative of migration elsewhere from the southern limits of breeding on rain‐fed vegetation, with inferred widespread adult mortality and renewed breeding most likely after migration on brief spells of southerly winds.
Resilience of the natural arthropod community on apple to external disturbance
Authors: BROWN M. W.
Published: March 2008

Abstract.

A naturally evolved arthropod community in a 6‐year‐old apple orchard was treated with three applications of permethrin; a second naturally evolved community was studied as an untreated control. Disturbance to the community was measured with Shannon's index of species diversity for the phytophagous and beneficial portions of the community.

Initially, there was a reduction in diversity of both phytophagous and beneficial arthropods because of the insecticide. Reduction in diversity was a result of both lower number of species and lower evenness of species abundance.

Two months after the last permethrin spray, there was no difference between diversity in the phytophagous community, but the beneficial community was more diverse in the treated orchard than in the untreated control.

The year after treatment there were few differences between the phytophagous communities, but the beneficial community was more diverse in the treated orchard than in the untreated orchard in May and early June; however, by September the beneficial community was less diverse in the treated orchard.

Although diversity statistics of the phytophagous communities were similar 15 months after treatment, differences still remained with the treated community being dominated by more r‐selected species and the control orchard dominated by more K‐selected species.

The arthropod community on apple has a high level of stability as reflected by its resilience to a severe external disturbance. This stability would allow for large, but infrequent, disturbances for pest management and still maintain long‐term ecological equilibrium in the community.