bluuebunny/crossref_metadata_2025_split huggingface dataset:
Altered dispersal behaviour in parasitised aphids: parasitoid‐mediated or pathology?
Authors: Chow A. , Mackauer M. 
Published: March 2003

Summary1. Several hypotheses concerning modified dispersal behaviour in aphids parasitised by aphidiine wasps (Hymenoptera: Braconidae: Aphidiinae) were tested in the laboratory. Behavioural changes may be host‐mediated, parasitoid‐mediated, or a by‐product of trauma and pathology.2. Mummification site varied with parasitoid species. Pea aphids (Acyrthosiphon pisum) parasitised by Aphidius ervi, Aphidius pisivorus, Monoctonus paulensis, and Praon pequodorum mummified near the aphids’ preferred feeding sites on bean plants, but those parasitised by Ephedrus californicus often died and mummified outside the colony, away from the plants.3. Parasitism by E. californicus had a progressive effect on the behaviour of pea aphids. Approaching death, aphids lost motor control and frequently dropped off the host plant when disturbed. Dropped aphids were unable to return to the feeding site and mummified elsewhere. The proportion of aphids mummifying outside the colony increased with mummy density.4. Mummification site was not influenced by the presence within the same colony of aphids parasitised by different species of aphidiine wasps.5. The evidence does not support the hypothesis that mummification site selection in E. californicus is determined by a host‐ or a parasitoid‐mediated change in aphid dispersal behaviour. Association‐specific differences in the dynamics of larval development and growth between aphidiine species provide an equally valid and possibly more general explanation of mummification behaviour.
Diversity and abundance of insect herbivores foraging on seedlings in a rainforest in Guyana
Authors: Basset YveS. 
Published: March 2003

Summary1. Free‐living insect herbivores foraging on 10 000 tagged seedlings representing five species of common rainforest trees were surveyed monthly for more than 1 year in an unlogged forest plot of 1 km2 in Guyana.2. Overall, 9056 insect specimens were collected. Most were sap‐sucking insects, which represented at least 244 species belonging to 25 families. Leaf‐chewing insects included at least 101 species belonging to 16 families. Herbivore densities were among the lowest densities reported in tropical rainforests to date: 2.4 individuals per square metre of foliage.3. Insect host specificity was assessed by calculating Lloyd’s index of patchiness from distributional records and considering feeding records in captivity and in situ. Generalists represented 84 and 78% of sap‐sucking species and individuals, and 75 and 42% of leaf‐chewing species and individuals. In particular, several species of polyphagous xylem‐feeding Cicadellinae were strikingly abundant on all hosts.4. The high incidence of generalist insects suggests that the Janzen–Connell model, explaining rates of attack on seedlings as a density‐dependent process resulting from contagion of specialist insects from parent trees, is unlikely to be valid in this study system.5. Given the rarity of flushing events for the seedlings during the study period, the low insect densities, and the high proportion of generalists, the data also suggest that seedlings may represent a poor resource for free‐living insect herbivores in rainforests.
Field studies on flooding and survival of overwintering large heath butterfly Coenonympha tullia larvae on Fenn’s and Whixall Mosses in Shropshire and Wrexham, U.K.
Authors: Joy J. , Pullin A. S. 
Published: March 2003

Summary1. Peatland rehabilitation projects may involve large increases in water levels if Sphagnum‐based vegetation is to be restored over areas where vegetation has largely been destroyed by commercial peat‐cutting processes. While this can result in the creation of cotton‐sedge tussocks Eriophorum vaginatum on which large heath butterfly Coenonympha tullia larvae live, the water level changes can also lead to these tussocks being subjected to long periods of winter flooding.2. Field trials were carried out over two winters (1996–97 and 1997–98) (1) to test laboratory predictions of the survival of C. tullia larvae under wet and dry conditions, (2) to record the behavioural responses of larvae to flooding, and (3) to determine whether vertebrate predation affected larval survival significantly.3. Field trials confirmed the results from earlier laboratory work in that they showed that the submergence of overwintering C. tullia larvae has a marked impact on their survival. During the 1996–97 winter, 35% of the larvae placed in wet areas survived compared with 63% placed in dry areas. During the 1997–98 winter, none of the C. tullia larvae placed in wet areas survived compared with 54% of the larvae placed in dry areas. Because the depth of flooding in the wet areas was much greater in the 1997–98 winter than in the 1996–97 winter, the results from this study may reflect the survival rates of wild C. tullia larvae under moderate (1996–97 data) or severe (1997–98 data) levels of flooding.4. The behavioural data from the field also support earlier laboratory findings and suggest that C. tullia can move in order to stay above the water surface. No evidence was found that vertebrate predation was a significant factor affecting larval survival.5. These results suggest that raised water levels threaten C. tullia populations, but that the maintenance of suitable E. vaginatum tussocks in drier areas may ensure that a proportion of the C. tullia population survives even the wettest years.
Effects of food plant and group size on predator defence: differences between two co‐occurring aposematic Lygaeinae bugs
Authors: Tullberg Birgitta S. , Gamberale‐Stille Gabriella , Solbreck Christer 
Published: March 2003

Summary1. The role of food plant and aggregation on the defensive properties of two aposematic sympatrically occurring seed bugs, Tropidothorax leucopterus and Lygaeus equestris (Lygaeinae, Heteroptera), was investigated. Larvae reared on seeds either of their natural host plant Vincetoxicum hirundinaria (Asclepiadaceae) or of sunflower Helianthus annuus were subjected to predation by chicks.2. The two species differ in their dependency on the host for their defence. Lygaeus equestris was better defended on its natural host plant than on the alternative food, as indicated by fewer attacks, lower mortality, and predator avoidance after experience. No such effect of food plant could be found for T. leucopterus, suggesting the existence of alternative defences in this species.3. The number of attacks was lower when host plant‐fed larvae of both species were presented in groups.4. The discussion concerns how major components of an aposematic syndrome, such as host plant chemistry, insect colouration, and aggregation, are integrated with other life‐history traits to form alternative lifestyles in L. equestris and T. leucopterus.
Humidity‐terminated diapause in the tropical braconid parasitoid Microplitis demolitor
Authors: Seymour Jamie E. , Jones Rhondda E. 
Published: March 2003

Summary1. Microplitis demolitor, a solitary braconid parasitoid of Helicoverpa armigera and Helicoverpa punctigera, uses an increase in relative humidity to signal the end of diapause and the re‐establishment of direct development.2. Photoperiod and temperature changes appear not to have a direct influence on the duration or termination of diapause in this species.3. Once diapause termination is signalled, the adult parasitoids emerge approximately 38 days later.4. The cue for diapause termination in M. demolitor is different from that used by its hosts and ensures that the parasitoid emerges to find a population of nonmigrating hosts.5. It appears that the cocoon surrounding the diapausing parasitoid plays a role in diapause termination; parasitoids emerge earlier from diapause if the cocoon is removed but the weight of the intact cocoon does not appear to influence the length of time the parasitoid is in diapause.
Structure of insect communities inhabiting old‐growth forest specialist bracket fungi
Authors: Komonen Atte 
Published: March 2003

Summary1. This paper describes the structure of the insect communities inhabiting two old‐growth forest specialist bracket fungi, Amylocystis lapponica and Fomitopsis rosea. To study the consequences of old‐growth forest fragmentation on community structure, non‐fragmented and fragmented forest areas in eastern and southern Finland were compared.2. Both fungal species are inhabited by more than 50 insect species. The most abundant species in the A. lapponica community is a melandryid beetle Hallomenus sp., and in the F. rosea community a tineid moth Agnathosia mendicella. The occurrence of several nationally or globally rare species underscores the importance of specific insect microhabitats, such as the specialist fungi A. lapponica and F. rosea, for the persistence of specialised insects in old‐growth forests.3. The species composition in both fungal species differs greatly from each other. The food webs are characterised by one numerically dominant host‐specific primary fungivore, which implies that fungivorous species inhabiting bracket fungi may be more specialised on a particular host than is generally thought.4. The community structure was the same in the highly fragmented and in the non‐fragmented study areas, probably because fragmentation has occurred relatively recently.
Male‐biased sex ratios in mature damselfly populations: real or artefact?
Authors: Stoks Robby 
Published: March 2003

Summary1. There is ongoing controversy about whether biased sex ratios in diploid insect populations are real or an artefact caused by different behaviours and/or different catchability of the sexes. This was tested by monitoring two field and three semi‐natural populations of the damselfly Lestes sponsa.2. Capture–mark–recapture data showed that population size estimates were about twice as large for males as for females at both field sites. Independent estimates of the sex ratios based on total numbers of males and females captured supported the male bias.3. Males had higher recapture probabilities than females due to longer times between successive visits in females. Because the same pattern was found in the semi‐natural populations, the longer intervals in females are no artefact due to their lower detectability.4. Theoretical models show that the strong temporary emigration of females tends, if anything, to overestimate female population sizes and that the heterogeneity of recapture probabilities observed in males tends to underestimate male population sizes. Hence, behavioural differences between the sexes do not cause an artificially male‐biased sex ratio.5. Spatial data show that operational sex ratios are male biased at the pond but become female biased in the plots further away from the shoreline; however because of the decrease in densities away from the shoreline, this does not result in a global even sex ratio.6. Spatial data, temporary emigration patterns, and independent estimates suggest strongly that the male‐biased sex ratios in mature damselfly populations are real.
Host plant growth characteristics as determinants of abundance and phenology in jumping plant‐lice on downy willow
Authors: Hodkinson Ian D. , Bird Jeremy M. , Hill Jane K. , Baxter Robert 
Published: March 2003

Summary1. Salix lapponum host plants at an upper altitudinal site differed significantly in size, structural density, phenology, growth performance, and spatial isolation from those growing at a lower site.2. Plant differences were paralleled by significant differences in psyllid population density and phenology parameters, with psyllid population density, percentage of catkins occupied, and phenological development relatively lower or retarded at the upper site. Population densities at the upper site, nevertheless, remained high.3. Plant measurements were good predictors of insect density, often explaining up to 73% of the variance in abundance among plants at a given site.4. Sets of four plant characters identified by best subsets regression were better predictors of psyllid density and development than single factors, although differences were often not great and the combinations of characters selected by multiple regression sometimes differed from the best single predictors.5. Best single predictors of psyllid density on catkins were measurements of plant size, particularly height, length, and basal stem diameter. Shoot density and catkin phenology were occasionally important but plant isolation and prior growth performance were less important.6. By contrast with density, age structure of the psyllid population was predicted best from plant phenological measurements, notably catkin phenology.
Population level correlation between pre‐alighting and post‐alighting host plant preference in the Glanville fritillary butterfly
Authors: Schöps Katrin , Hanski Ilkka 
Published: March 2003

Summary1. In many populations of the Glanville fritillary butterflyMelitaea cinxia, ovipositing females exhibit a post‐alighting preference for one of the potential host plant species available. The work reported here aimed to establish whether females with different post‐alighting preferences can discriminate between their host plant species prior to alighting, and whether pre‐alighting and post‐alighting preferences are correlated at the population level.2. Alighting and oviposition events were recorded for groups of females from six populations in greenhouse and field experiments.3. Landing frequencies did not change with experience, indicating thatM. cinxiafemales did not learn from previous encounters with host plants.4. Females from populations exhibiting post‐alighting preference searched efficiently for their host plants in the sense that they landed mainly on the species on which they oviposited predominantly. Pre‐alighting and post‐alighting preferences were correlated at the population level.5. The correlation between pre‐alighting and post‐alighting preferences helps to explain why in nature, where the host plants often occur in distinct patches, females are more likely to colonise habitat patches in which their preferred host plant is abundant.
Autumnal moth – why autumnal?
Authors: Tammaru Toomas , Tanhuanpää Miia , Ruohomäki Kai , Vanatoa Alo 
Published: March 2003

Summary1. As for some other spring‐feeding moths, adult flight of Epirrita autumnata (Lepidoptera: Geometridae) occurs in late autumn. Late‐season flight is a result of a prolonged pupal period. Potential evolutionary explanations for this phenological pattern are evaluated.2. In a laboratory rearing, there was a weak correlation between pupation date and the time of adult emergence. A substantial genetic difference in pupal period was found between two geographic populations. Adaptive evolution of eclosion time can thus be expected.3. Metabolic costs of a prolonged pupal period were found to be moderate but still of some ecological significance. Pupal mortality is likely to form the main cost of the prolonged pupal period.4. Mortality rates of adults, exposed in the field, showed a declining temporal trend from late summer to normal eclosion time in autumn. Lower predation pressure on adults may constitute the decisive selective advantage of late‐season flight. It is suggested that ants, not birds, were the main predators responsible for the temporal trend.5. Egg mortality was estimated to be low; it is thus unlikely that the late adult period is selected for to reduce the time during which eggs are exposed to predators.6. In a laboratory experiment, oviposition success was maximal at the time of actual flight peak of E. autumnata, however penalties resulting from sub‐optimal timing of oviposition remained limited.
Instar‐specific sensitivity of specialist Manduca sexta larvae to induced defences in their host plant Nicotiana attenuata
Authors: Van Dam Nicole M. , Hermenau Uta , Baldwin Ian T. 
Published: March 2003

Summary1. The time delay associated with the activation of induced defences is thought to be a liability for this type of defence because it allows herbivores to remove biomass before the defence is fully induced. When defences are costly and plants grow with competitors, however, it may be more advantageous not to induce defences too fast and motivate the herbivore to move to the neighbour when it is most voracious.2. Such a strategy can only work when the costs for the herbivore of moving to a neighbouring plant are smaller than the costs of staying on a fully induced plant. For lepidopteran herbivores, both the sensitivity to induced defences and the costs of moving may vary considerably between instars and this variation may constrain the plant's defensive opportunities.3. This study was designed to examine whether the cost of moving, mimicked by a starvation period of 8 h, was larger than the cost of staying on a fully induced plant for each larval instar of the specialist Manduca sexta feeding on induced and control tissues of Nicotiana attenuata.4. For first‐ and second‐instar larvae, the costs of moving were larger than the costs of staying on a fully induced plant. In contrast, feeding on induced plant material retarded development in third‐instar larvae more than did starvation, indicating that in this instar the costs of leaving are smaller than the costs of staying on an induced plant. More than 98% of the lifetime leaf mass consumed by a M. sexta larva is consumed during the fourth and fifth instars, and during these instars larval development was not affected by either induced defences or starvation. Thus the third instar, the stage just before larvae cause the majority of damage, represents a window of sensitivity to induced defences during which larvae can be motivated to change plants.5. These results suggest that N. attenuata plants, which commonly compete with conspecifics in nature, have the opportunity to manipulate the behaviour of the specialist herbivore M. sexta to minimise the fitness effects of inducing defences when these defences are most costly, i.e. when plants grow under intraspecific competition.
Task‐partitioned nectar transfer in stingless bees: work organisation in a phylogenetic context
Authors: Hart Adam G. , Ratnieks Francis L. W. 
Published: March 2003

Abstract 1. The eusocial corbiculate bee tribes comprise the Apini (honey bees), Bombini (bumble bees), and Meliponini (stingless bees). Honey bee foragers (Apis) transfer nectar to receiver bees within the nest. This is an example of task partitioning, in which a task is split into sub‐tasks connected by material transfer. Nectar transfer does not occur in Bombini. Although it is reported in some species of Meliponini, it has not been subject to detailed study.2. Nectar transfer was investigated in five genera of Meliponini from Yucatan, Mexico (Melipona, Trigona, Scaptotrigona, Nannotrigona, and Plebeia). Nectar transfer occurred in all species and for > 99% of foragers. Multiple transfer, in which a forager unloads nectar to more than one receiver, occurred but at a lower level than in Apis. In M. beecheii, multiple transfer was associated strongly with putative recruitment dances.3. The data provide some support for the hypothesis that task partitioning is favoured by large colony size, in that the Meliponini never have small colonies because colonies are swarm founded. This ensures that colonies are always large enough to prevent delays in finding a transfer partner imposing high costs. Further tests of this hypothesis are suggested.4. Viewed in a phylogenetic context, the most parsimonious interpretation is that nectar transfer evolved once in the clade (Apini + Meliponini).
Cornicle length in Macrosiphini aphids: a comparison of ecological traits
Authors: Mondor Edward B. , Roitberg Bernard D. , Stadler Bernhard 
Published: March 2003

Abstract 1. Aphids often emit cornicle droplets when attacked by predators. While the function of cornicle droplets has long been debated (i.e. mechanical protection vs. chemical signalling), it is not understood why aphid species have cornicles of different lengths.2. It was hypothesised that aphids living in more scattered colonies have longer cornicles to scent‐mark predators with cornicle droplets containing alarm pheromone, so that clone‐mates are provided with advanced warning of a threat, even if not at the predation site. To test this hypothesis, multiple regression analyses were used, due to a lack of phylogenetic information on these taxa, to address which ecological traits (amount of wax on an aphid, degree of colony aggregation, feeding shelter, ant attendance) are correlated with cornicle length.3. Aphids living in dense colonies tended to have shorter cornicles than aphids living in more scattered colonies. Also, aphids with more protection (i.e. wax) on their bodies had shorter cornicles. Aphids also tended to have shorter cornicles when tended by ants. The presence of a feeding shelter was not a good predictor of cornicle length.4. It is suggested that longer cornicles function to scent‐mark predators with alarm pheromone to increase the inclusive fitness of a clone; however the negative correlation between the amount of individual protection, and also ant attendance, and cornicle length argues for a trade‐off between different forms of defence.
A review of competition in north temperate dung beetle communities
Authors: Finn John A. , Gittings Tom 
Published: March 2003

Abstract.1. Studies of north temperate dung beetle communities frequently invoke competition as an influential ecological process. In this review, the evidence for competition in north temperate dung beetle communities is evaluated and the role of competition as a factor affecting community structure is assessed.2. Resource limitation and the evidence for interspecific competition are assessed by collating the available experimental and observational evidence for both the adult and larval stages of the dung beetle life cycle. The role of competition as a structuring force in dung beetle communities is discussed under the following headings: niche dynamics, migration to and from individual pats, the aggregation model of co‐existence, and metapopulations.3. Some of the main conclusions are that competition for space is much more likely to occur than competition for food; the effects of competition on community structure are poorly understood; several of the influential studies of competition in north temperate dung beetle communities need to be evaluated carefully. The differences in ecology between tropical and temperate dung beetle communities are clarified.4. As priorities for future research, resource utilisation and competition should be researched experimentally: density‐dependent relationships should be investigated, particularly for the larval stages, as should competitive interactions with other dung fauna. If such experimental approaches establish convincingly the occurrence of competition, then the extent of competition in the field and under real world conditions needs to be established. A functional group classification of dung beetles and other dung fauna is described, which may improve the generality of interpretation from individual, site‐specific results.