bluuebunny/crossref_metadata_2025 huggingface dataset:
Ejaculate size varies with socio‐sexual situation in an insect
Authors: GAGE MATTHEW J. G. , BAKER R. ROBIN
Published: March 2008

Abstract.

Males operate within a finite energy budget and cannot produce limitless supplies of sperm. On the other hand, when a female mates with a second male while still containing fertile sperm from a rival male, selection should favour the male that inseminates more sperm. Optimal strategy should thus be for males to exercise discretion in the allocation of sperm to individual females. Assuming the outcome of sperm competition to be based on either the raffle or kamikaze principles, the sperm competition hypothesis predicts a positive association between the probability that the sperm will find themselves in competition with sperm from rival males and the number of sperm inseminated.

The beetle, Tenebrio molitor L., behaves in accordance with this hypothesis. Males accompanied by a rival male before and during mating inseminate more sperm per ejaculate than unaccompanied males. Accompanied males are also faster to initiate mating and more likely to show post‐copulatory guarding. Adjustment of number of sperm inseminated was shown by males subjected to both long‐term (5 days) and short‐term (5 min) exposure to potential intrasexual competitors. Individual males exposed to both levels also demonstrated the ability to adjust their ejaculate according to socio‐sexual situation.

We conclude that male T.molitor adjust the number of sperm they inseminate according to some perception of the risk of sperm competition.
The size relationship between insects and their hosts
Authors: KIRK WILLIAM D. J.
Published: March 2008

Abstract.

Regressions of adult insect size on host size were tested. The analysis was restricted to highly host‐specific insects that had thus been exposed to a narrow range of host size.

The phylogenetic regression method was used to analyse the data, so as to allow for the possible phylogenetic effects in cross‐species data.

Significant positive regressions were found in all the groups tested: female flower thrips, Meligethes species of pollen beetle, tephritid flies, and male and female fleas. They were also found by standard regressions within. and between Actornithophilus species of bird louse.

The regression of thrips size on pollen size was not significant, providing evidence against a hypothesis involving food size.

The regression of flea body size on host hair/feather length was significant, which is consistent with a hypothesis involving the size of spaces on the host.

The relationships may have implications for the understanding of evolutionary host shifts.
Host stress influences oviposition preference and performance of a pine sawfly
Authors: TISDALE ROBERT A. , WAGNER MICHAEL R.
Published: March 2008

Abstract.

The effect of ponderosa pine (Pinus ponderosa Doug]. ex Laws) water stress, measured by xylem water potential, on oviposition preference and egg development of Neodiprion fulviceps was determined by two laboratory experiments in 1987 and 1988.

In the first experiment, adult females were allowed to choose between foliage from water‐stressed, watered, and untreated control trees.

Significant differences were found between treatments in xylem water potential in 1987 but not in 1988.

Females chose water‐stressed trees and a positive correlation was found between female preference and xylem water potential in 1987 but not in 1988.

In the second experiment, females were placed in globe cages with a single branch from each treatment and allowed to oviposit.

Significant differences were found among treatments in egg survival in 1987 but not in 1988.

These results indicate that sawflies can distinguish between stressed and non‐stressed trees and that this behaviour is adaptive in that egg survival was greatest on the preferred treatment.
Patterns of host selection by four species of aphidiid (Hymenoptera) parasitoids: influence of host switching
Authors: CHOW A. , MACKAUER M.
Published: March 2008

Abstract.

We tested switching behaviour in four species of aphidiid parasitoids, using a two‐aphid experimental system consisting of second‐instar nymphs of pea aphid (Acyrthosiphon pisum (Harris)) and alfalfa aphid (Macrosiphum creelii Davis) feeding on broad beans in the laboratory.

Aphidius ervi Haliday, A.pisivorus Smith, A.smithi Sharma & Subba Rao, and Pram pequodorum Viereck showed an innate preference for pea aphid when both host species were provided in equal numbers.

Wasps encountered both aphid species equally but differed in their acceptance of alfalfa aphid. Females of A.pisivorus and P.pequodorum accepted alfalfa aphids when few pea aphids were available, but A. smithi always concentrated attacks on pea aphid. Aphidius ervi super‐parasitized an increasing proportion of pea aphids as their availability declined.

Switching to the alfalfa aphid occurred in A.ervi and P.pequodorum (but not in A.pisivorus and A.smithi) under the condition of a 1:3 ratio of pea aphids:alfalfa aphids. Wasps did not switch when more pea aphids than alfalfa aphids were provided (3:1 ratio).

Alfalfa aphids were more likely than pea aphids to escape from parasitoid attack.

Switching to the most abundant host may not be adaptive in these four species of aphid parasitoids. A foraging wasp incurs a potentially higher cost in lost opportunity time when attacking (and failing to oviposit in) alfalfa aphids. In addition, alfalfa aphids may have lower host quality than pea aphids, a difference that could influence offspring fitness.
Nectar sugar and amino acid preferences of Battus philenor (Lepidoptera, Papilionidae)
Authors: ERHARDT ANDREAS
Published: March 2008

Abstract.

Butterflies of Battus philenor were tested for their preferences for nectar sugars and amino acids in an outdoor cage experiment.

The butterflies clearly preferred both sucrose and fructose over glucose. They also preferred sucrose over fructose.

No other preferences were found to be statistically significant, although male butterflies tended to prefer a plain sugar solution over a sugar solution containing a mixture of amino acids: females consumed both of these solutions in almost equal proportions.

The results are discussed with respect to nectar composition of butterfly pollinated flowers, flower preferences, physiological and reproductive aspects of butterflies.
The long‐distance migration of Nilaparvata lugens (Stål) (Delphacidae) in China: radar observations of mass return flight in the autumn
Authors: RILEY J. R. , XIA‐NIAN CHENG , XIAO‐XI ZHANG , REYNOLDS D. R. , GUO‐MIN XU , SMITH A. D. , JI‐YI CHENG , AI‐DONG BAO , BAO‐PING ZHAI
Published: March 2008

Abstract.

A case study is presented of the autumn migration of the brown planthopper, Nilaparvata lugens (Stål), in the area of Nanjing in the People's Republic of China. The study was made using a high frequency (8 mm wavelength) radar and a net suspended from a kytoon.

The observations confirmed that long‐distance return migrations occur in China in mid and late September, with N.lugens being carried on the prevailing north‐easterly wind towards the autumn infestation and overwintering areas of the species.

After mass take‐off in the late afternoon or at dusk, the migrants flew for several hours during the evening, often in a dense layer which formed at heights between about 400 and 1000m above ground. These layers often had well‐defined ceilings corresponding to an air temperature of about 16°C. The migration height was above the top of the surface temperature inversion, i.e. the migrants did not fly at the height of the warmest air.

The dense layer concentrations overflying the radar were backtracked to source areas up to 240 km away in the north‐east of Jiangsu Province. Planthoppers observed emigrating from the Nanjing area would reach areas in south Anhui Province or north Jiangxi Province if they flew for 12 h.

There was a second period of mass take‐off at dawn. Insect layers sometimes formed but did not last longer than 1–2h.

The present results were strikingly different from those previously observed in the dry season in the Philippines, where migratory flight durations were largely confined to periods of about 30min at dusk and dawn.

Our observations are discussed in relation to the equator‐wards return migrations undertaken in autumn by other insect species, and the importance of these migrations for the maintenance of long‐flying genotypes in the overwintering populations is considered.
How many species are there in apple insect communities?: testing the resource diversity and intermediate disturbance hypotheses
Authors: SZENTKIRÁLYI F. , KOZÁR F.
Published: March 2008

Abstract.

In European and American apple orchards the insect species richness, calculated from our own, and published data, varied widely (30–940 species). The dominance of insect orders was similar to that found in natural communities.

To test the predictions of the‘resource diversity hypothesis’(RDH) and the‘intermediate disturbance hypothesis’(IDH) of insect diversity, we analysed the simultaneous impact of vegetational diversity and intensity of orchard management practice on the species richness of characteristic insect categories in six types of apple stands, over 5 years, in Hungary.

The more diverse was the vegetation adjacent to the orchard and the less intensively was the orchard managed, the greater was the total insect species richness, supporting both hypotheses.

The number of agricultural pest species found in the apple orchards depended above all on the diversity of adjacent agricultural vegetation, supporting only the RDH.

The species richness of specialized apple pests was limited only by the intensity of pest control, supporting only the IDH.

Within the category of generalist natural enemies species richness mainly varied with the diversity of adjacent vegetation, supporting the RDH.

The aeroentomofauna constituted a surprisingly high percentage (>50%) for both total species and agricultural pests, but was poorly represented within the natural enemies category, and absent from the specific apple pest category.

A general conclusion is that the number of insect species in perennial orchard‐systems within agricultural areas is determined primarily by the regional extra‐orchard vegetational diversity and secondly by the degree of local intra‐orchard disturbances and plant diversity. Consequently, at the community level the predictions of both hypotheses can be simultaneously valid at different spatial scales and are not mutually exclusive. However, within the community, at the level of the different insect categories studied here, only one of the hypotheses proved to be valid.
Influence of leaf traits on the spatial distribution of arboreal arthropods within an overstorey rainforest tree
Authors: BASSET YVES
Published: March 2008

Abstract.

Several attributes of foliage were measured from the Australian rainforest tree Argyrodendron actinophyllum Edlin (Sterculiaceae). These were related to estimates of abundance per leaf area of the most common arthropod guilds and families sampled with restricted canopy fogging.

When all these arthropod groups were considered, much of the overall variance in arthropod spatial distribution could be attributed to leaf age characteristics, arthropod aggregation patterns, arthropod activity and distance to tree trunk.

The fraction of variance which could be specifically explained by foliage attributes such as nitrogen‐, water‐ and fibre‐content, specific leaf weight, and epiphyll load was small for most arthropod groups (usually <30%). However, an index of food quality explained a higher proportion of variance (50%) in the abundance of phloem‐feeders. Leaf size and foliage compactness did not influence significantly the abundance of any arthropod group.

Most herbivores were more abundant on young foliage than on mature leaves. With the exception of Corylophidae and Chrysomelidae, which were more abundant in the lower and upper canopy respectively, arthropod stratification was not conspicuous within the inner core of tree crowns.

The results firstly emphasize the distribution of young foliage as a key factor affecting the abundance of many herbivores and, secondly, the importance of the local illumination regime for host leaf production and its indirect effects on the spatial distribution of arboreal arthropods.
Patterns of nest provisioning and parental investment in the solitary digger wasp Ammophila sabulosa
Authors: FIELD JEREMY
Published: March 2008

Abstract.

In nest‐building wasps there is a continuum from species that provision each offspring cell with one large prey item (single provisioning) to species that provision each cell with many small items (multiple provisioning). The significance of number of prey per cell was examined during two seasons in Ammophila sabulosa (L.), a species that provisions between one and five caterpillars per cell.

There was no difference between the total weight of prey in singly‐provisioned and multiply‐provisioned cells: individual caterpillars placed in multiply‐provisioned cells were smaller.

Small caterpillars were captured and transported to the nest faster than large ones.

If the first prey provisioned was large, the cell was usually then permanently closed. If the first prey was small, additional prey were captured, and females appeared to become more selective: additional prey were rarely large.

It is suggested that the flexible provisioning strategy used by A.sabulosa allows a wide range of prey sizes to be utilized without affecting maternal control of offspring size and sex. This could be important when available prey sizes vary temporally and spatially.

There was a male‐biased first generation investment ratio. Female‐producing cells were provisioned with a higher total prey weight than male‐producing cells, and conversion of prey weight to adult weight was more efficient for females.

Total prey weight provisioned is probably a good indirect measure of parental time investment in A.sabulosa. Other measures, particularly number of prey provisioned, will be less accurate.
Interpopulation differences in pupal size and fecundity are not associated with occurrence of outbreaks in Epirrita autumnata (Lepidoptera, Geometridae)
Authors: RUOHOMÄKI KAI , HAUKIOJA ERKKI
Published: March 2008

Abstract.

Among‐population differences in pupal mass were studied in a geometrid, Epirrita autumnata. Some Epirrita autumnata populations regularly reach outbreak densities while others are never known to do so. Because adults do not feed, pupal mass of females correlates strongly with fecundity.

Larvae were collected from twelve field sites. Ten of our sample populations originated within the outbreak range of the species and represented different phases of outbreaks. Two populations originated outside the outbreak range.

Pupal mass of field‐collected E. autumnata varied significantly among populations. The peak phase populations had the smallest pupae and the biggest were found in low density populations outside the outbreak range.

Offspring of moths from each population were reared under identical conditions in two larval densities. Significant differences were not found in pupal mass among populations. That is, the inherent size, correlated with fecundity of moths, was not different between populations originating within and outside the outbreak range, nor among collections from different densities or phases of the outbreaks.

Rearing density did not interact in a consistent way with population.

As far as size and fecundity are concerned, the results do not support Chitty's hypothesis that differences in genetic composition of the population at low and high density phases generate cyclic fluctuations of population density.

Because no hereditary or maternal differences were found in size and fecundity between E.autumnata originating within and outside the outbreak range, variation in reproductive capacity cannot explain why outbreaks occur only in some populations.
Adaptive superparasitism in solitary parasitoids: marking of parasitized hosts in relation to the pay‐off from superparasitism
Authors: VISSER MARCEL E. , LUYCKX BART , NELL HENK W. , BOSKAMP GÉ J.F.
Published: March 2008

Abstract.

The pay‐off from an egg laid in a parasitized host is an important parameter in models on adaptive superparasitism in solitary insect parasitoids.

For Leptopilina heterotoma, a parasitoid of larval Drosophila, the pay‐off from a second egg laid in a host is 0.43 offspring when the interval between the two ovipositions is less than 3h. For longer intervals, this pay‐off decreases to almost zero for an interval of 24 h.

When a female encountering a parasitized host is able to estimate the interval since the first oviposition, it is expected that she will take this into account in her host selection decisions. This is, however, not in the direct interest of the female that lays the first egg, and marks the host.

We studied whether superparasitism in hosts containing a young egg is more common than in hosts containing an older egg, when searching in a patch containing once‐parasitized and unparasitized hosts.

The acceptance/encounter ratio of parasitized hosts increased for intervals longer than 6h, as predicted when the interests of the marking female and the longevity of the mark are taken into account.

Superparasitism occurred more often when parasitoids had previously searched a host patch 7 days before the experiment compared to when parasitoids had searched a patch 1 day before, a phenomenon predicted by dynamic optimal diet models.
Oviposition choice and larval survival of Dasineura marginemtorquens (Diptera: Cecidomyiidae) on resistant and susceptible Salix viminalis
Authors: LARSSON STIG , STRONG DONALD R.
Published: March 2008

Abstract.

Substantial intraspecific variation exists in Salix viminalis resistance to the gall midge Dasineura marginemtorquens. Earlier work has found this variation to have a large genetic component. Willow clones are stable in their resistances between midge generations and different nutrient levels in both field and laboratory culture.

This study reports the results of laboratory experiments on female oviposition choice and larval survival on potted plants from clones that are very different in resistance as determined in field studies.

In choice experiments using pairs of plants, the average female midge did not prefer susceptible willow clones over resistant ones for oviposition. In about one third of the replicates, midges actually laid more eggs on the resistant clone. Further work is necessary to examine the nature of variation among midges in discrimination of these plant types.

Resistance is manifested as great differences in larval survival. Six days after oviposition survival was 92% on susceptible plants but only 6% on resistant ones. Galls developed on all of the susceptible plants, while in 73% of the resistant plants galls were not even initiated.

The plant traits causing resistance are enigmatic. Larval behaviour suggests that resistant plants interfere with feeding behaviour. On resistant plants, most larvae wander for more than 24 h without initiating any galls before dying. On susceptible plants many first instar larvae begin feeding and initiate galls within this period.
Cost of shield defence for tortoise beetles (Coleoptera: Chrysomelidae)
Authors: OLMSTEAD KAREN L. , DENNO ROBERT F.
Published: March 2008

Abstract.

Tortoise beetle larvae possess a shield composed of exuviae and faeces which functions as an effective defence against some invertebrate predators.

In the laboratory,Charidotella bicolor, Deloyala guttataandChelymorpha cassidealarvae with their shields experimentally removed did not exhibit enhanced performance (i.e. decreased development time, increased body mass, or higher survival) compared to control larvae with shields intact.

Disturbance caused during shield removal did not adversely affect larvae because performance did not differ among controls (undisturbed larvae with intact shields), disturbance controls (shield removal simulated, but shield left in place), and larvae with shields removed.

Larvae without shields did not exhibit compensatory feeding to reconstruct the shield following its removal.

In a field experiment in which predators were excluded, larvae with shields removed did not develop faster than controls; in fact, survival was slightly reduced (10%) for larvae without shields and may have resulted from desiccation.

For slow‐moving tortoise beetle larvae, the cost of bearing the shield is minimal. Thus, larval shields, composed of recycled waste products, provide an inexpensive mode of protection from some natural enemies.
The extinction and foundation of local butterfly populations in relation to population variability and other factors
Authors: POLLARD E. , YATES T. J.
Published: March 2008

Abstract.

Definitions were adopted for the identification of the extinction and foundation of populations in data from the Butterfly Monitoring Scheme from 1976 to 1991. The data are indexes of abundance, not population estimates.

The frequency of extinctions and foundations for twenty‐eight butterfly species was assessed in relation to characteristics of their population fluctuations, as indicated by fluctuations in the index values.

Using multiple regression, the best predictive equation for the number of extinctions plus foundations included the number of test data available, the mean index per site and the first serial correlation. Two measures of variability were included in the analysis, but were not retained in the best predictive equation.

Some results for individual species are described and the potential of the approach for the study of effects of climatic warming is emphasized.
Behaviour of specialist and generalist caterpillars on plantain (Plantago lanceolata)
Authors: STAMP NANCY E. , BOWERS M. DEANE
Published: March 2008

Abstract.

Foraging patterns of specialist (Junonia coenia Hubner: Nymphalidae) and generalist (Spilosoma congrua Wlk.: Arctiidae) caterpillars on five genotypes of plantain (Plantago lanceolata L.: Plantaginaceae) were examined in an experimental garden.

Movement by the specialists reflected declining availability of new leaves. When direct sunlight was available, these caterpillars were usually exposed to it.

Although the generalists also preferred new leaves, they spent less than 50% of their time on the plantain and changed location more frequently than the specialists. They often hid at the base of plants or under leaves.

Plant genotype influenced the apparency of the specialists and damage by the herbivores.
Monogamy to communal breeding: exploitation of a broad resource base by burying beetles (Nicrophorus)
Authors: TRUMBO STEPHEN T.
Published: March 2008

Abstract.

To investigate the range of resource size that burying beetles (Nicrophorus) exploit, small (21–33 g), medium (50–90 g) and large (120–210g) carcasses, were placed in the field and then exhumed after 1, 4, 8, 12 or 18 days.

Nicrophorus attempts to utilize carcasses over this entire size range but has greater success on smaller carcasses.

Larger carcasses were more difficult to exploit because: (a) they took longer to conceal beneath the leaf litter; (b) they were less likely to be rounded into brood balls; (c) they were more likely to be utilized by dipterans; and (d) they were occupied by greater numbers of congeners.

Larger carcasses, however, did support greater numbers of larvae and contained broods of greater total mass than smaller carcasses.

Beetles sometimes bred communally on larger carcasses in the field and same‐sex adults were observed to feed young.

Two follow‐up experiments were conducted in the laboratory. On a large carcass N.defodiens, N.tomentosus or N.orbicollis can raise a maximum of 35–50 young. Nicrophorus pustulatus, in contrast, appears to be unique among Nicrophorus in that it can raise nearly 200 young on larger carcasses.

Nicrophorus orbicollis and Nicrophorus sayi are extremely dependent on parental regurgitations and young fail to survive to the second instar if parents are removed. Young of Nicrophorus defodiens, N.tomentosus and N.pustulatus can develop normally without parental regurgitations.

I discuss these results in the context of reproduction on carcasses of different size and hypothesize that this breeding system is facultatively quasisocial.
Abundance and stratification of foliage arthropods in a lowland rain forest of Cameroon
Authors: BASSET YVES , ABERLENC HENRI‐PIERRE , DELVARE GERARD
Published: March 2008

Abstract.

Arthropod densities and apparent leaf damage were compared within the canopy ecotone and the shrub layer of a lowland rain forest in Cameroon, using a branch clipping method.

Most of the individuals collected consisted of ants (average 44%) and various herbivores (31%). Overall arthropod densities amounted to 17 individuals per sample, which, on average, consisted of 0.85 m2of foliage area. Arthropod densities were lower than on temperate foliage.

Arthropod densities were about 3 times higher in the canopy than within the shrub layer. In particular, ants and herbivores were significantly more abundant in the canopy than within the shrub layer. Usually, layer effects rather than site effects appeared to cause greater variance in arthropod abundance.

Arthropod species‐richness, as estimated by the number of operational taxonomic units sorted, was higher in canopy samples than in samples obtained from the shrub layer. However, apparent leaf damage was higher within the shrub layer (10.9%) than on the canopy (5.2%).

Possible factors responsible for the high densities of ants and herbivores on the canopy and for the high leaf damage within the shrub layer are discussed.
The swarming behaviour of the Scottish biting midge, Culicoides impunctatus (Diptera: Ceratopogonidae)
Authors: BLACKWELL ALISON , MORDUE (LUNTZ) A. JENNIFER , YOUNG MARK R. , MORDUE WILLIAM
Published: March 2008

Abstract.

Swarms of Culicoides impunctatus males were examined in the field in Scotland. Most swarms were close to midge emergence/breeding grounds over a variety of vegetation, some of which clearly acted as swarm markers. Low light (0–1000 lux) and still/humid conditions favoured swarming.

Swarm size ranged between less than 10 and more than one thousand midges. The modal size was 200 individuals. The smallest swarms were usually columnar in shape and the larger swarms ovoid.

Midges behaved individually within swarms, moving in an elliptical manner characteristic of other dipterans in swarms.

Swarms were classified as either ‘persistent’ or ‘transient’ in terms of their shape, size and stability. Wind was the most influential factor in disrupting swarms.

Swarms were confirmed as mating sites for C.impunctatus.
Foraging by honeybees on Carduus acanthoides: pattern and efficiency
Authors: GIURFA MARTIN , NÚÑEZ JOSUÉ A.
Published: March 2008

Abstract.

The relationship between the fluctuation in total quantity of sugar available in the nectar of Carduus acanthoides inflorescences and the foraging behaviour of honeybees Apis mellifera ligustica was studied in a patch under natural conditions.

Every day, three inflorescence populations coexisted, one for each day of the inflorescence life‐span. The maximum availability of sugar occurred in second‐day capitula from 12.00 to 15.00 hours.

Bee arrivals at the patch were positively correlated with the total availability of sugar as determined by sampling.

Bees responded to variation in the availability of sugar by visiting the inflorescence stage that was most rewarding at that time of day. Early in the morning, when the frequency of visits was low, the bees worked the third‐day capitula, which were the best available choice at that time. Similarly, beginning at 12.00 hours, bees switched to second‐day capitula. At the end of the day, some bees switched to third‐day capitula where a slightly superior quantity of sugar could be obtained from a small number of florets although other bees continued to work the second‐day capitula.

Individual bees switched to another inflorescence stage after a high proportion of their visits to a small number of capitula of one kind had provided a low reward.

The number of florets visited per minute per bee varied throughout the day and was positively correlated with the availability of sugar.
Population studies of Cheilosia fasciata (Diptera: Syrphidae), a leaf miner of Allium ursinum
Authors: HÖVEMEYER K.
Published: March 2008

Abstract.

Population dynamics of Cheilosia fasciata were described based on a sampling programme covering all developmental stages.

Failure to oviposit and mortality which was due to parasitization of pupae contributed most to total generation mortality.

Abundance of older larvae was regulated by density‐dependent intraspecific competition for food.

These findings were reinforced by a field experiment which manipulated food levels and suggested that losses in numbers on ‘low food’ plots were in part compensated for by producing low‐sized adults.
Adjacent trophic‐level effects on spatial density dependence in a herbivore—predator—parasitoid system
Authors: CAPPUCCINO NAOMI
Published: March 2008

Abstract. 1. Spatial density dependence of enemy/victim relationships (predator/prey and host/parasitoid) were examined for the gall‐making herbivore Eurosta solidaginis (Diptera: Tephritidae), its predator Mordellistena unicolor (Coleoptera: Mordellidae), and a parasitoid of Mordellistena, Schizoprymnus sp. (Hymenoptera: Braconidae), both before and after experimental perturbation of gall density.

2. Mordellistena predation did not depend on Eurosta density, nor did Schizoprymnus parasitism of Mordellistena depend on Mordellistena density.

3. Schizoprymnus parasitism of Mordellistena depended strongly on the density of Eurosta, the prey of its host.

4. The lack of density dependence in enemy/victim relationships may be explained by effects from adjacent trophic‐levels. Ovipositing Schizoprymnus may search for high densities, not of its host Mordellistena, but of its host's prey (Eurosta galls), and ovipositing Mordellistena may avoid patches of high gall density where the risk of being parasitized is greater.
Does gall diameter affect the parasitism rate of Asphondylia borrichiae (Diptera: Cecidomyiidae)?
Authors: ROSSI ANTHONY M. , STILING PETER D. , STRONG DONALD R. , JOHNSON DEREK M.
Published: March 2008

Abstract. 1. Fertilized field plots of Borrichia frutescens (L.) de Candolle produced plants with a higher apical‐leaf nitrogen content than control plots.

2. Gall frequency of the cecidomyiid Asphondylia borrichiae Rossi & Strong on stems of B.frutescens, increased significantly on fertilized plots after approximately 3 months.

3. Fertilizer treatment did not result in changes in stem density but did tend to increase proportion of stems flowering and overall plant size. Galls are not normally found on flowering stems.

4. Galls grew at a faster rate and to a larger final size on fertilized plots.

5. On three sampling dates, per cent parasitism of galls was the same on fertilized and control plots; therefore, this study does not support the galldiameter hypothesis.
Brood raiding and the population dynamics of founding and incipient colonies of the fire ant, Solenopsis invicta
Authors: TSCHINKEL WALTER R.
Published: March 2008

Abstract. 1. One of the first activities of minim workers in incipient fire ant nests is mutual brood raiding, the amalgamation of nests through the reciprocal stealing of brood and defection of workers.

2. Discrete mating flights created cohorts of incipient colonies. About 25% of founding nests survived the claustral period of 16–48 days (depending on season). Early incipient colony mortality was 5–6% per day. Over 60% of this mortality was accounted for through brood raiding. Most colonies raided when each cohort first became active, and many raided more than once. Raid size (number of nests, duration, distance) tended to increase during the summer as colonies grew through raiding. After the raiding period, nest mortality rate dropped 3–10‐fold. Only 1–3% of founding nests were still alive at this time.

3. Queens from losing or failed nests tended to abandon their nests and attempted to enter successful ones, often following raiding trails to do so. This emigration was at least as successful as non‐emigration in ultimately achieving the status of reproductrix of a successful nest (about 4%).

4. Brood raiding is a dominant process in early population dynamics, probably accounting for most of the early nest mortality. Its effect is to change the venue and unit of competition from nest‐against‐nest to a shifting aggregation of queens, workers and brood involving entire local populations. Nest thinning is thus very rapid, and the boost to the size of winning nests very large, allowing raiding colonies to win the competition for territory, and to achieve the early colony maturity so important to this, and other, weedy species. The importance of winning brood raids may also have driven increased minim production through the evolution of pleometrosis.
The metazoan food webs from six BorneanNepenthesspecies
Authors: CLARKE C. M. , KITCHING R. L.
Published: March 2008

Abstract.

Two contrasting hypotheses concerning patterns in food web structure within pitchers ofNepenthesare tested using new information from six species ofNepenthesfrom Borneo.

In general, predictions that webs will be more complex, and the food chains they contain will be longer, the closer they are to the centre ofNepenthesspecies diversity, are supported.

ForNepenthes albomarginata, a widespread species with a distinctive north Bornean form, a contrasting pattern is evident explicable in terms of the morphology of the pitchers and local habitat preferences.

General explanations for food web patterns will always be susceptible to exception, reflecting nuances of natural history.
The nutritional quality of phloem sap utilized by natural aphid populations
Authors: DOUGLAS A. E.
Published: March 2008

Abstract.

The amino acid content of phloem exudates from leaves and of aphid honeydew were adopted as indices of the nutritional quality of phloem sap for aphids. Four plant species and associated leaf‐dwelling aphids were investigated: the sycamore Acer pseudoplanatus and sycamore aphid Drepanosiphum platanoides; Prunus domestica (victoria plum) and the mealy plum aphid Hyalopterus pruni; and the spindle tree Euonymus europaeus and broad‐bean Vicia faba, both hosts of the black bean aphid Aphis fabae.

The concentration of amino acids in the phloem exudates varied with: (a) plant species (greater in the herb Vicia than in the tree species), (b) season (greater in the autumn than summer for Acer and Euonymus), and (c) position (greater in flush leaves than mature leaves of Prunus).

For Acer and Prunus and their aphids, the concentration of amino acids in phloem exudates was significantly correlated with the amino acid content of the aphid honeydew.

The amino acids in all exudates and honeydew were dominated by non‐essential amino acids (glutamic acid, glutamine, asparagine or serine, varying with season and between plant species). The sole major discrepancy between the amino acid profiles of exudates and honeydew was the production of asparagine‐rich honeydew by aphids feeding on leaves, whose exudates were dominated by glutamic acid; this applied to both H.pruni on mature Prunus leaves and Drepanosiphum platanoides on summer‐leaves of Acer.

It is suggested that EDTA‐exudation may be a useful technique to study nutritional correlates of aphid life cycles, e.g. the time of migration between primary and secondary plant hosts.
Phenotypic plasticity and geographical variation in the pre‐reproductive period of Autographa gamma (Lepidoptera: Noctuidae) and its implications for migration in this species
Authors: HILL JANE K. , GATEHOUSE A. GAVIN
Published: March 2008

Abstract.

Adults of the noctuid moth Autographa gamma undertake seasonal migrations into areas where they are unable to breed continuously. Individuals migrate into Britain each spring, and offspring of these migrants probably return in autumn to over‐wintering areas in North Africa and the Middle East. However, the existence of these return migrations has been questioned.

Insects usually migrate during the adults' pre‐reproductive period (PRP). The length of this period is therefore an index of migratory potential since individuals with longer PRPs have more time to express their potential for flight and to travel further before becoming sexually mature.

Offspring of insects from Morocco, Britain and Germany showed that, under both long and short photoperiods, PRP increased with latitude over the range 34–53°N. There were significant genotype—environment interactions in the effect of photoperiod on length of PRP.

However, PRPs of offspring from insects collected in Sweden were no different under a long photoperiod from those of offspring collected further south, and were significantly shorter under a short photoperiod than those of insects from Morocco.

With the exception of Swedish moths, offspring from insects collected at higher latitudes had longer PRPs and, therefore, the potential to travel further during migrations. The ability of some individuals to respond to environmental cues signalling habitat deterioration will further increase their potential to return to over‐wintering areas further south.
Do host alternating aphids know which plant they are on?
Authors: KUNDU R. , DIXON A. F. G.
Published: March 2008

Abstract.

To determine whether an aphid is ‘aware’ of which plant it is on, clones of a host alternating aphid, Cavariella aegopodii Scop., reared on its primary (Salix) or secondary (Daucus) host, were subjected to autumnal conditions.

Old clones produced males and egg laying females when exposed to autumnal conditions on the primary host but autumnal migrants and males when on the secondary host.

Unlike some other host alternating aphids, Cavariella did not have to spend a period on the secondary host or go through the spring migrant stage before producing sexuals.

The adaptive significance of a host alternating aphid being ‘aware’ of which host plant it is on is discussed in the light of these results.
Contest competition among Maculinea rebeli butterfly larvae in ant nests
Authors: THOMAS J. A. , ELMES G. W. , WARDLAW J. C.
Published: March 2008

Abstract.

Caterpillars of the myrmecophilous butterfly Maculinea rebeli showed strong evidence of contest competition when introduced at high densities to laboratory nests of Myrmica ants.

This is attributed to the direct feeding of caterpillars by workers, which select a few individuals to nurture when food or ant numbers are limiting. It contrasts with published data for a congener, Maculinea arion, which has predacious larvae and experiences scramble competition in crowded ant nests.

Worker ants from two Myrmica rubra colonies (I and II) were used to found the laboratory nests hosting Maculinea rebeli. Nests from each source reared a similar biomass of Maculinea, but whereas those containing M. rubra I workers reared eight to ten lightweight caterpillars each, cultures from colony II reared half as many caterpillars, each of about double the weight.

Differences in nest capacity may be due to the different social structures of colonies I and II at the start of the experiment.
Calculation of collated indices of abundance of butterflies based on monitored sites
Authors: MOSS D. , POLLARD E.
Published: March 2008

Abstract.

The Butterfly Monitoring Scheme uses regular transect counts on fixed sites to establish annual indices of abundance of butterfly species in the United Kingdom. The annual change in collated index for each species has hitherto been calculated as a simple ratio between total counts summed over all participating sites.

A revised method for calculation of collated indices is proposed, which applies a logarithmic transformation to site values so as to downweight the influence on the index of the sites with greatest numbers of a species. Zero counts are handled comparably with non‐zero values. An alternative method using geometric mean ratios is also examined.

Indices calculated using the logarithmic transformation are compared with those calculated using the traditional method. Two internal tests of dependency of collated indices on the sites with highest abundance are made. Another evaluation uses regression analysis for the effects of temperature and rainfall on collated indices of butterfly abundance.

The first internal test shows that logarithmic transformation reduces the dependence of the collated index on the sites of highest abundance for twenty‐five out of twenty‐seven species examined; while a second test shows a reduction for twenty‐six out of forty‐two species, and an increase for one species. The number of significant regressions on temperature variables increases with the use of the logarithmic transformation from 11% to 13% of tests made, and on rainfall from 10% to 11%.

The geometric mean ratio method introduces considerable biases in its treatment of zero values, for which a remedy is not available.

Although the revised collated indices calculated using logarithmic transformation are broadly comparable with traditionally calculated values, the reductions in dependency on sites with the most abundant populations render the revised indices less subject to perturbation due to local ‘noise’, and so more suitable for research on factors influencing butterfly abundance.
Ecology of body size in Drosophila buzzatii: untangling the effects of temperature and nutrition
Authors: THOMAS RICHARD H.
Published: March 2008

Abstract.

A method of separating the effects of two important determinants of body size in natural populations, temperature of larval development and level of larval nutrition, by making measurements of thorax length and wing length of adult flies is investigated.

I show that at any given time variation in body size of Drosophila buzzatii from two sites in eastern Australia is determined primarily by variation in the quality of nutrition available to larvae.

Throughout the year adult flies are consistently at least 25% smaller in volume than predicted for optimal nutrition at their predicted temperature of larval development.

Nutritional stress is therefore a year‐round problem for these flies.

Measurements of adult flies emerging from individual breeding substrates (rotting cactus cladodes) show that there is substantial variation among these substrates in the nutrition available to larvae.

This method will allow study of spatial and temporal variation in the temperature of larval substrates and in the nutritional resources available to flies in natural populations.
Fluctuating asymmetry and lifetime mating success are correlated in males of the damselfly Coenagrion puella (Odonata: Coenagrionidae)
Authors: HARVEY IAN F. , WALSH KITT J.
Published: March 2008

Abstract.

The influence of fluctuating asymmetry on lifetime mating success of males of the damselfly Coenagrion puella (Odonata: Coenagrionidae) was investigated. Fluctuating asymmetry was measured as the difference in length of left and right fore and hind wings.

Males with more symmetrical wings enjoyed higher lifetime mating success.

Larger males, in contrast to a previous study of this species, also had higher mating success. This may be attributed to differences in the weather conditions prevailing at the time of the studies.
The arthropod predators of ant‐mimetic and aposematic prey: a serological analysis
Authors: McIVER JAMES D. , TEMPELIS CONSTANTINE H.
Published: March 2008

Abstract.

ELISA (enzyme‐linked immunosorbant assay) was used to identify the arthropod predators of two common herbivores of a desert lupine: the aposematic plant bug Lopidea nigridea and the ant‐mimetic plant bug Coquillettia insignis.

Despite the fact that the prey are closely related, the two antisera were sufficiently specific to distinguish between the antigen against which they were formed and the antigen of the other species: both antisera were 3 times as reactive against their homologous antigen as they were against their heterologous antigen.

In tests on gut contents of field‐collected predators, ELISA results were generally consistent with laboratory no‐choice data for the five most common arthropod species on lupine: there was a strong correlation between attack rates for each predator‐prey pair as measured in the laboratory, and per cent positive reactions in ELISA as measured using field‐collected predators. In particular, L.nigridea antiserum was shown to be significantly less reactive against the crab spider Xysticus montanensis when compared to C.insignis antiserum, paralleling results of laboratory no‐choice experiments.

The usefulness of serological analysis as a tool for arthropod trophic link identification is discussed.
A nectar‐secreting gall wasp and ant mutualism: selection and counter‐selection shaping gall wasp phenology, fecundity and persistence
Authors: SEIBERT T. F.
Published: March 2008

Abstract.

The natural history of a gall wasp including interactions with inquilines, parasites, and a mutualistic ant are examined. The stability of the system is described from the perspective of influences on gall wasp life history characteristics.

An exclusion experiment demonstrated that the nectar‐secreting gall of Disholcaspis perniciosa mediates a mutualism with the tending ant, Formica obscuripes. Survivorship increased from 0% in the absence of ants to 25.3% in their presence, largely due to the exclusion of inquilines.

Specialized parasites, Eudecatoma spp., attacked before the ant‐gall interaction began, when the developing gall was still beneath the host plant (Quercus gambellii) epidermis and ants were not in attendance. They may select for later developing gall wasps, which benefit by having fewer individuals parasitized. However, counter‐selection for earlier development may result from decreased gall wasp size, decreased fecundity, and an increase in gall failures resulting from late development.

Local persistence of the gall wasp population despite increased pressure from inquilines and parasites was attributed to gall wasp escape in time due to polymorphic emergence resulting from diapause. Most individuals emerge at the end of the summer, but approximately 15% remain in the galls as prepupae for 1–5 years.
Fire ant predation on native and introduced subterranean termites in the laboratory: effect of high soldier number in Coptotermes formosanus
Authors: WELLS JEFFREY D. , HENDERSON GREGG
Published: March 2008

Abstract.

Native Reticulitermes spp. Holmgren and the introduced Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae) were exposed to predation in the laboratory by Solenopsis invicta Buren (Hymenoptera: Formicidae), a known predator of Reticulitermes.

In one experiment, both taxa contained the 2.4% soldiers commonly found in Reticulitermes. In a second experiment, Reticulitermes contained 2.4% and C.formosanus a more normal 18.3% soldiers.

When soldier proportions were equal, C.formosanus soldiers suffered less of a decrease in survivorship due to predation compared with Reticulitermes soldiers. Little difference was found between taxa in the effect of predation on termite workers or in the effect of termites on predator survivorship.

When soldier proportions were unequal, both C.formosanus castes suffered less from predation than those of Reticulitermes. Again, little difference was found in the effect of termites on ants.

C.formosanus showed less movement into new containers when soldier number was abnormally low, compared with both taxa with normal caste proportions.
Relationships between abundance and body size: where do tourists fit?
Authors: GASTON KEVIN J. , BLACKBURN TIM M. , HAMMOND PETER M. , STORK NIGEL E.
Published: March 2008

Abstract.

The possible effects of the inclusion of ‘tourist’ species have been the cause of some concern in investigations of interspecific relationships between abundance and body size.

Data for adult beetles (Coleoptera) from oak trees in Britain are used to investigate the relationship of abundance to body size when tourists are and are not included.

For this particular assemblage, tourists do not fundamentally alter the basic statistics of the relationship between abundance and body size. However, they are not a random sample of the beetle assemblage. They have lower abundances and are also of smaller body size than other species.