bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.