bluuebunny/crossref_metadata_2025 huggingface dataset:
Radar observations of the spring migration into northeastern China of the oriental armyworm moth, Mythimna separata, and other insects
Authors: RUI‐LU CHEN , XIANG‐ZHE BAO , DRAKE V. A. , FARROW R. A. , SU‐YUN WANG , YA‐JIE SUN , BAO‐PING ZHAI
Published: March 2008

Abstract. 1. The spring migration of the oriental armyworm moth, Mythimna separata (Walker), and other insects into northeastern China was observed by radar at a site in central Jilin province. Samples of the migrants were obtained in a net flown from a kite, and M.separata populations in the surrounding region were monitored with a trap network.

2. The radar regularly detected echoes which were of the type characteristic of large insects, and three out of four large insects in the aerial samples were noctuid moths, including one M.separata. Catches of armyworm moths in the regional trap network peaked during the period of radar observations.

3. Migration occurred at night. It commenced with a take‐off flight at dusk and generally continued until dawn, with numbers often being highest around midnight. Most migration took place at altitudes below 500 m, with strong layer concentrations forming at 200–400 m during the middle part of some nights.

4. Migration was approximately downwind. The net movement was overwhelmingly to the northeast because southwesterly winds occurred most frequently and were relatively strong, and because migration was more intense and prolonged on these winds. Orientation tended to be to the left of the downwind direction, and was most often to the north or northeast.

5. Migration into northeastern China was accomplished in a series of night‐time movements of 100–300 km rather than by a single non‐stop flight.

6. The net movement of insects towards the northeast was sufficient to produce the observed regional infestation of M.separata moths. Oviposition by immigrant armyworm moths in vulnerable crops would have been at a level where economically significant damage would be expected from the resulting larval population.

7. Analogous springtime migrations of noctuids leading to temporary colonizations of habitats at higher latitudes occur in other continents. Such colonizations may be unproductive if, as appears possibly the case for northeastern China, prevailing winds later in the season are generally unfavourable for a return migration towards overwintering areas at lower latitudes.
Plant resistance, plant traits, and host plant choice of the leaf‐folding sawfly on the arroyo willow
Authors: FRITZ ROBERT S. , NOBEL JENNIFER
Published: March 2008

Abstract. 1. The hypotheses that genetic variation in host plant resistance of the arroyo willow affected leaf folder (Phyllocolpa sp.) (Hymenoptera: Tenthredinidae) density and that genetic variation in shoot length and leaf length was correlated with resistance were tested.

2. Willows grown in pots and exposed to ovipojsition by the leaf folding sawfly in cages had significantly different densities among clones, indicating variation in resistance caused by genetic differences among conspecific host plants.

3. There was a general correspondence between leaf folder density on potted cuttings and on the plants in the field that were the sources of cuttings.

4. In behavioural choice experiments, susceptible clones (with highest leaf fold densities) had the highest oviposition activity of female leaf folders compared to clones that were resistant to the leaf folder.

5. Clones differed significantly in shoot length and leaf length among clones grown in pots, among clones in the field, and between shoots with galls and shoots without galls on clones in the field.

6. Leaf folder density was significantly positively correlated with mean shoot length on field clones in 1985 and 1986, but was not correlated with leaf length, although leaf length and shoot length were correlated.

7. Leaf length variation among willow clones accounted for a significant portion of the variation in resistance of potted willows, but shoot length was unimportant.
Taxonomy, attack strategies and host relations in flowerhead Tephritidae: a review
Authors: STRAW N. A.
Published: March 2008

Abstract. 1. Host relations of Palaearctic flowerhead‐inhabiting tephritids (Diptera: Tephritidae) are reviewed in terms of the interaction between type of attack strategy and flowerhead size.

2. Three types of attack strategy are recognized, each associated with a particular phase of Compositae flowerhead development. These strategies are characteristic of a tribe or subfamily, viz the Tephritini (Tephritinae), Terelliini (Tephritinae) and Myopitinae.

3. Tephritini species show the most generalized feeding method, and this enables them to attack both large and very small flowerheads. In contrast, the more specialized requirements of members of the Terelliini and Myopitinae apparently restricts these groups to plant taxa with large flowerheads. As a result, over the whole range of Compositae flowerhead sizes, there exists a positive relationship between flowerhead size and the diversity of associated tephritids.

4. The occurrence of stem‐feeding tephritids, and differences between a coevolutionary and functional (colonization) explanation for tephritid host‐relations are discussed.
Iridoid glycosides and insect feeding preferences: gypsy moths (Lymantria dispar, Lymantriidae) and buckeyes (Junonia coenia, Nymphalidae)
Authors: BOWERS M. DEANE , PUTTICK GILLIAN M.
Published: March 2008

Abstract. 1. The effect of increasing concentrations of an iridoid glycoside, catalposide, was tested on a generalist and an adapted specialist lepidopteran, using artificial diets.

2. Two strains of the gypsy moth, Lymantria dispar (L.) (Lymantriidae), were tested. Larvae of a wild strain showed a negative dose‐dependent response to increasing concentrations of catalposide (up to 7.2% dry weight), while a laboratory strain showed no such pattern. Choice tests using the laboratory strain showed that these larvae often preferred diets relatively low in catalposide over those with higher concentrations.

3. In contrast, larvae of the iridoid glycoside specialist, the buckeye, Junonia coenia Hübner (Nymphalidae), showed a positive dose‐dependent response and grew better on diets with higher doses of catalposide.

4. We tested whether the improved growth of J. coenia at higher concentrations of catalposide may have been due to extra glucose yielded by hydrolysis of catalposide. Larvae were fed increasing doses of glucose equivalent to the amount potentially obtained by hydrolysing the quantities of catalposide used in the previous experiment. However, added glucose did not effect growth, suggesting that increased growth at higher catalposide concentrations was due to increased feeding rates.
The potential for interspecific competition between two abundant defoliators on oak: leaf damage and habitat quality
Authors: HUNTER M. D. , WILLMER P. G.
Published: March 2008

Abstract.1. The pedunculate oak, Quercus robur L., suffers high annual levels of spring defoliation in Wytham Woods, Oxon. The two major defoliators, Tortrix viridana L. and Operophtera brumata L., sometimes reach high enough densities to completely defoliate trees.

2. Experiments with larvae of both species enclosed on oak trees in Wytham Woods suggest considerable potential for intra‐ and interspecific competition between T. viridana and O. brumata.

3. T. viridana and O. brumata consume equivalent amounts of leaf tissue per unit caterpillar density. Despite this, O. brumata is the superior competitor, measured by mortality during the larval feeding period.

4. Evidence is presented that T. viridana larvae depend upon the protected microclimate of leaf rolls to maintain water balance, and that leaf damage may disrupt the construction of, and microclimate within, leaf rolls. O. brumata may therefore be competitively superior because it indirectly interferes with the water balance of T. viridana.

5. The importance of interspecific competition in the dynamics of T. viridana and O. brumata populations is discussed. Stochastic mortality factors acting on first instar larvae of both species probably make intense competition a rare event.
Age‐associated male mating success in three swarming caddis fly species (Trichoptera: Leptoceridae)
Authors: PETERSSON ERIK
Published: March 2008

Abstract. 1. In the three caddis fly species, Athripsodes albifrons (L.), A. cinereus (Curtis) and Mystacides azurea (L.) (Leptoceridae; Trichoptera), males swarm above the water surface of lakes or rivers. Receptive females fly to swarms and are chased and/or courted by males. After one of the swarming males has grasped an approaching female, the pair flies in tandem to the shore where they copulate.

2. In males, wing wear indices were negatively correlated with the ratio of fat/dry weight. In the only species in which comparisons were possible between newly emerged and swarming males (M. azurea), the former had significantly lower indices. Unmated females on average had lower wing wear indices than spent females. These facts suggest that wing wear reflects relative age.

3. The tandem males had significantly less wing wear than those in swarms, and are probably therefore younger. Age is therefore likely to be significant in relation to mating success.

4. Among males of the same relative age, tandem males had higher fat ratio than swarming ones, indicating that male mating success was also influenced by traits other than age. It is suggested that the shortest possible duration of the period of adult prematurity is adaptive, especially in insects with marginal adult food intake.
Field estimation of variation in host plant use between local populations of pea aphids from two crops
Authors: VIA SARA
Published: March 2008

Abstract. 1. In a reciprocal transplant experiment on pea aphids (Acyrthosiphon pisum (Harris)), the relative performance of clones collected from nearby alfalfa and red clover fields was tested by allowing clonal replicates to develop on both crops under field conditions.

2. Populations from alfalfa and red clover differed in relative survivorship and probabilities of reproduction on the two crops. Clones had significantly higher performance on the crop from which they were collected (the ‘home’ crop) than they did on the other crop.

3. Evidence is presented that previous experience on these host plants cannot account for the increased probability of reproduction observed on the ‘home’ crop. Thus, the differences between these two populations in their relative performance on alfalfa and clover are likely to be genetically based.

4. These results illustrate that local adaptation to different host plants can occur within small geographical areas, despite the high probability that migrants are exchanged between nearby fields of the two crops.

5. Experimental designs of the type described here permit estimation of patterns of genetic variation within and between insect populations. When applied to pest species, such designs will facilitate the study of evolution in agricultural systems.
Gallery construction and oviposition of the bark beetle Ips typographus (Coleoptera: Scolytidae) at different breeding densities
Authors: ANDERBRANT OLLE
Published: March 2008

Abstract. 1. The bole of a Norway spruce, Picea abies(L.) Karst., was cut in 25 cm sections and infested in the laboratory with 2 or 8 females/dm2 of Ips typographus (L.) and an equal number of males.

2. One log of each beetle density was dissected every second day, beginning 2 days after female introduction.

3. The oviposition rate was highest at the beginning of the breeding period for both densities and then declined, especially at the high density. Residence time is a useful approximation for the number of laid eggs in the beginning of the oviposition period or when the density is low.

4. Final gallery length and egg number per gallery were on average significantly smaller at density 8 than at density 2.

5. Linear relationships between total gallery length and number of egg niches were found to be similar for the two densities.

6. An estimate of the egg to adult mortality at different densities was found by using data from a field study that related gallery length to breeding density in attacked living trees, together with published relationships between density and egg niches or emergence of new adults.

7. It was concluded that both decreased oviposition rate and earlier re‐emergence at higher densities contribute to a declining oviposition with increasing density. The final offspring production is futher reduced by lower survival due to larval competition as density increases.
Colony success of the submissive ant Formica fusca within territories of the dominant Formica polyctena
Authors: SAVOLAINEN RIITTA
Published: March 2008

Abstract. 1. Twenty‐three nests of the submissive ant Formica fusca L. were sampled in two adjacent territories of the dominant wood ant Formica polyctena Först. The nests were dug up at different distances from the wood‐ant mounds. Distance is assumed to be inversely related to the extent of disturbance of F. fusca by F. polyctena.

2. Colony success of F. fusca was assayed by counting the numbers of workers (colony size), and worker and sexual offspring in a nest. For individual size, the head width and dry weight of fifty workers per nest were measured.

3. Colony size correlated positively with the numbers of worker and sexual offspring in one territory, but only with worker offspring in the other.

4. Distance from the wood‐ant mound correlated positively with colony size and numbers of worker and female offspring in one territory. In the other territory distance correlated positively with number of females, but negatively with number of worker offspring. No significant correlations between distance and the size measurements were obtained.

5. Because of its nonaggressive behaviour F. fusca may nest fairly close to a wood‐ant mound but is likely to show reduced abundances in terms of nest density and forager number, and, ultimately, lowered fitness.
Nuptial gift size prolongs copulation duration in the dance fly Empis borealis
Authors: SVENSSON BO G. , PETERSSON ERIK , FRISK MICHAEL
Published: March 2008

Abstract. 1. The time that pairs of the dance fly Empis borealis (L.) (Diptera: Empididae) spent in copula was positively correlated with the volume of the nuptial gift.

2. In some cases the copulation duration was short although prey volume was large. Females engaged in these matings had more worn wings, were therefore older, and most probably had sperm already stored in the spermatheca. It is suggested that these copulations were interrupted because either the spermatheca was full of sperm and the male was not able to transmit any sperm, or because prey content was depleted (males may have fed on the prey or the prey had been used in a previous mating). The latter explanation seemed more probable.

3. A male providing a large nuptial gift may transfer larger quantities of sperm. Quantitative sperm competition is more likely than last‐male sperm predominance.
Variation of density‐dependence with spatial scale in the leaf‐mining fly Liriomyza commelinae (Diptera: Agromyzidae)
Authors: FREEMAN B. E. , SMITH D. C.
Published: March 2008

Abstract. 1. Mortality imposed on the leaf mining fly, Liriomyza commelinae (Frost) was studied at three spatial levels: (1) the leaf, (2) the stem, and (3) a metre quadrat of the food plant.

2. Real mortality (R.M.) (death as a percentage of eggs laid) during development for five sites over 3 years (forty‐seven generations) was 96.3 + 1.9% ‐2.5% (±95% c.l.), due mainly to parasitoids and predatory ants, with a small component due to competition and other causes.

3. Real mortality due to the parasitoid complex averaged 41.2%. It was not related to population density in leaves or stems but was positively dependent on density in one metre quadrats.

4. Predation by Crematogaster brevispinosa Mayr was 21.2% and was independent of population density at all spatial levels.

5. Mortality due to other causes (e.g. competition and exposure to high temperature resulting from insolation) was positively dependent on the number of mines per leaf at three out of five sites studied and the number of mines per stem at two of the three sites studied; however, such mortality was independent of density per metre quadrat.
Nest thermoregulation in Vespa simillima, V.tropica and V.analis
Authors: MARTIN STEPHEN J.
Published: March 2008

Abstract. 1. Nest thermoregulation follows a similar pattern in Vespa simillima Smith and V. tropica L. There is a gradual decline in the daily fluctuations of nest temperature to a constant steady state which is maintained during the production of the first sexuals, followed by a sudden loss of stability at the end of the colony cycle.

2. The larvae are not major producers of heat, as they are unable to raise their body temperature by more than 1–2°C above ambient. However, they act as heat reservoirs and providers of food in the form of larval secretions. This feeding may allow workers to raise their body temperature during non‐foraging periods.

3. The adults are capable of raising their body temperature many degrees above ambient and the presence of even one adult, in this case a V.analis F. mother queen, was able to raise the nest temperature.

4. Supplementary carbohydrate food promotes thermogenesis and enhances colony development.
Host refuges and spatial patterns of parasitism in an endophytic host–parasitoid system
Authors: ROMSTÖCK‐VÖLKL MARIA
Published: March 2008

Abstract. 1. Larvae of Tephritis conura Loew (Diptera: Tephritidae) live gregariously in flower heads of Cirsium heterophyllum (L.) Hill (Cardueae). They are attacked by the endoparasitic wasps Eurytoma sp. near tibialis Boheman (Hymenoptera: Eurytomidae) and Pteromalus caudiger (Graham) (Hymenoptera: Pteromalidae).

2. The responses of the parasitoids to different host patch sizes were investigated from the analysis of field samples. At the host population level, overall probabilities of parasitism were independent of host numbers per flower head or showed a tendency to inverse density‐dependence for both parasitoid species.

3. Measurements of ovipositor length in Eurytoma and P.caudiger indicated that parts of the flower head constitute a structural refuge from parasitism.

4. The accessibility of hosts in a flower head was found to differ markedly, depending on larval locations and flower head characters. In spite of this high variability, similar average percentages of larvae were accessible to the parasitoids in each patch size class.

5. High variability of oviposition success in laboratory experiments can be explained by random locations of hosts in the flower heads.
Interference competition among burying beetles (Silphidae, Nicrophorus)
Authors: TRUMBO STEPHEN T.
Published: March 2008

Abstract. 1. This study investigated the impact of intraspecific and interspecific competition on the reproductive success of a biparental burying beetle, Nicrophorus defodiens Mannerheim.

2. Marked pairs or single females were placed on small and large mouse carcasses in the field in 1985 and 1986. Carcasses were exhumed after 9–10 days to determine the identity of the resident adult(s) and the production of young.

3. Competition was assessed by the prevalence of takeovers by intruders (unmarked adults). For N.defodiens, after the initial colonization of the carcass, interspecific competition from larger N.orbicollis Say and N.sayi Laporte was substantial and more intense than intraspecific competition. Competition was also greater in the middle of the breeding season and on large as opposed to small carcasses.

4. Successful takeovers resulted in the expulsion of the prior resident(s), killing of any offspring present on the carcass, and oviposition of a new clutch by the intruder.

5. Females aided by males were more likely than single females to avoid takeovers but did not produce larger broods or larvae of larger mass.

6. An additional laboratory experiment in 1985 and a field experiment in 1986 suggest that N.defodiens is able to reproduce on very small carcasses despite intense heterospecific activity.
Absence of intraspecific interference during feeding by the predatory ladybirds Chilocorus spp. (Coleoptera: Coccinellidae)
Authors: HATTINGH VAUGHAN , SAMWAYS MICHAEL J.
Published: March 2008

Abstract. 1. The hypothesis was tested that intraspecific behavioural interference does not adversely affect the feeding behaviour of adults of three predatory coccinellid species, Chilocorus nigritus (F.), C.bipustulatus (L.) and C.infernalis Mulsant, at densities found under field conditions.

2. Feeding rates on mature oleander scale Aspidiotus nerii Bouché were evaluated by two methods at various predator densities. Proportion of the population dispersing was also measured for one of the species.

3. Feeding rate did not decrease and dispersal did not increase with increasing predator density. No significant behavioural interference that might have reduced predatory efficiency was observed, counter to assumptions on which published interference models are based.

4. Results here help to explain the relative importance of parasitoids and predators in the effective control of red scale Aonidiella aurantii (Mask.). The results also provide guidelines for release of these bio‐control agents.
Significance of spring migration and flexibility in flight‐muscle histolysis in waterstriders (Heteroptera, Gerridae)
Authors: KAITALA ARJA , HULDÉN LARRY
Published: March 2008

Abstract. 1. Individuals of long‐winged waterstrider (Gerridae) species were found in spring far from their breeding habitats, which indicates that they fly before reproduction.

2. Field samples and laboratory studies show that once they return to their breeding sites, many individuals of three waterstrider species (Gerris odontogaster (Zett.), Gerris lacustris (L.) and Limnoporus rufoscutellatus (Lat.)) histolyse wing muscles and lose flight ability during their reproductive period.

3. The extent of flight‐muscle histolysis varies with environmental factors. Food scarcity affects flight‐muscle histolysis in G.odontogaster females. In G.Lacustris, flight‐muscle histolysis was more common in the laboratory than in the field samples. Proportionately more females than males lost their flight ability by the end of the reproductive period.

4. Flight ability had direct costs in reproductive potential with (non‐flyer) females, which histolysed their flight muscles, laying more eggs than (flyer) females, which maintained flight ability. This was also the case during food scarcity. Non‐flyer males of G.odontogaster survived longer than flyer males.

5. Spring migration was distinguished from dispersal during the reproductive period, because these flights serve different functions. Flight‐muscle histolysis of females during reproduction is a qualitative reproductive option, with a trade‐off between dispersal ability and reproductive potential. Ability to change reproductive behaviour depending on environmental conditions increases an individual's ability to cope with a large variety of habitats.
The effects of survival and weather on lifetime egg production in a model damselfly
Authors: THOMPSON DAVID J.
Published: March 2008

Abstract. 1. A simulation model is presented which describes, from field‐estimated parameters, the effects of daily survival rate and proportion of sunny days on the lifetime egg production of females of the damselfly Coenagrion puella (L).

2. Lifetime egg production increases with daily survival rate and proportion of sunny days.

3. Estimates of mean lifetime egg production per female in bad and good summers in northern England ranged from 333 to 740.

4. The distribution, as well as the proportion, of sunny days influences lifetime egg production. For a given combination of daily survival and proportion of sunny days, lifetime egg production decreases as the distribution of sunny days becomes more clumped.

5. Lifetime egg production is largely determined by chance; females who begin their mature adult life during a period of sunny weather can produce many times more eggs than those whose mature adult life coincides with cloudy days.
Differential resource utilization and co‐occurrence of leaf miners on oak (Quercus dentata)
Authors: SATO HIROAKI
Published: March 2008

Abstract.

Spatial, temporal, and dietary differences in resource utilization and patterns of interspecific association on leaves were investigated for dominant and common leaf‐mining species on an oak species, Quercus dentata Thunb., in Hokkaido, northern Japan.

Leaf miners were divided into two groups according to leaf tissues used for food: upper‐layer‐feeders which consume the palisade paren‐chymatous layer (Stigrnella spp. and tenthredinid sp.), and full‐depth‐feeders which consume spongy and palisade parenchymatous layers (Phyllonorycter leucocorona (Kumata), P.similis Kumata, and Caloptilia sapporella (Matsumura)).

Differences in the position of mines on leaves were found among species: mines of P.similis were distributed more frequently in the middle section of leaves, whereas those of the remaining species were concentrated in the basal section.

Leaf size preference differed between species: C.sapporella and tenthredinid sp. tended to select larger leaves more frequently than did the other species.

Phenological differentiation was found among species: C.sapporella appeared earliest, followed by P.similis, P.leucocorona and a tenthredinid sp., and then Stigmella spp.

Each species showed a highly clumped distribution among leaves. Leaf miners of some species pairs co‐occurred on leaves more frequently than expected by chance.
Fitness and habitat segregation of British tree‐hole mosquitoes
Authors: BRADSHAW W. E. , HOLZAPFEL C. M.
Published: March 2008

Abstract.

Populations of three mosquitoes, Aedes geniculutus (Olivier), Anopheles plumbeus Stephens and Culex torrentium Martini, were found in three types of tree holes: rot holes penetrating the bark of the host tree and exposed, or deeper, more cryptic, bark‐lined buttress holes. Aedes geniculatus occupied all three tree‐hole types but reached their greatest abundance in exposed buttress holes; A.plumbeus predominated in rot holes; C.torrentium occupied buttress holes exclusively.

After a 1 month period of winter freezing, larvae of A.plumbeus survived better than larvae of A. genicularus. Freeze resistance of A.plumbeus increased from cryptic buttress to rot holes. Freeze resistance of A.geniculatus declined from exposed buttress to cryptic buttress to rot holes and was markedly higher in more protected than in more exposed macrohabitats.

Among manipulated larval cohorts of A.geniculutus and A.plumbeus, survivorship, pupation success, pupal weight, and/or biomass yield did not differ among tree‐hole types or was the reverse of freeze‐related survivorship. Despite seasonal differences in fitness correlates, annual fitness may be similar among tree‐hole types for both species. Manipulations carried out at a single census or during a single season are therefore likely to produce misleading information about fitness variation among sub‐habitats.

Both species should exploit a broad range of tree‐hole types but A.plumbeus occupies more restricted types of tree holes than does A.geniculutus. The restricted habitat usage by A.plumbeus does not parallel their fitness among tree‐hole types in southern Britain but does resemble that of other tree‐hole anophelenes. We therefore propose that habitat selection by A.plumbeus is more likely due to their phylogenetically determined physiological tolerances and behaviour than to competition from coexisting A.geniculatus.
Multiple mating and its effect on the reproductive success of female Epiphyas postvittana (Lepidoptera: Tortricidae)
Authors: DANTHANARAYANA W. , GU H.
Published: March 2008

Abstract.

Multiple mating and its effect on reproductive performance of female Epiphyas postvittana (Walker) moths were studied under controlled conditions.

The age at which the moths mated for the first time ranged from the first to the tenth day after emergence, but 71% of first matings were during the first 3 days.

The majority (63%) of females had one or two spermatophores in the bursa copulatrix. Some (24%) were found with three to five spermatophores, whereas no successful mating occurred among 13% of individuals. The number of matings was partly dependent on the number of mates available to the female. Between the range of sex ratios of one male to one female and four males to one female maximal mating success occurred at the ratio of three males to one female.

Virgin females were capable of egg‐laying, but mating stimulated and accelerated oviposition. Mated individuals laid twice as many eggs as unmated ones.

The level of copulatory activity did not influence the longevity of females irrespective of the number of males available to them.

Sex ratios with greater than one male to a female improved the reproductive success by marginally increasing fecundity and fertility.

It is concluded that multiple mating would enhance population growth, and is of particular benefit to populations with a preponderance of females, as is known to occur naturally in this species.
Is foraging in the desert ant, Messor pergandei (Hymenoptera: Formiceidae), limited by water?
Authors: FEENER DONALD H. , LIGHTON JOHN R. B.
Published: March 2008

Abstract.

The seed‐harvesting ant Messor (Veromessor) prrgandei (Mayr) is a common inhabitant of southwestern deserts of the U.S.A. Foragers vary in size from less than 1 mg to more than 10 mg in body mass and may travel over 80 m on a single foraging trip. Their small size, long foraging range, and hot, arid habitat suggest that water stress may limit foraging activity. We examined intercolony and interindividual variation in water loss of M.pergandei foragers under several different situations in the field.

Colonies differed significantly in minimum critical water content (Wc) of individual foragers (water content below which foragers are incapable of normal locomotion). In one colony small workers had disproportionately higher Wc than larger workers; in the other colony Wc was isometric with body size.

Groups of workers confined in the field approached Wc only after normal foraging stopped and substrate temperatures exceeded 45°C, while water content of individual foragers did not approach the Wc during normal foraging periods. Moreover, seed load and distance travelled did not negatively affect forager water content, as measured on return to the nest: indeed, our results suggest that forager hydration level may influence load selection and/or foraging distance. We conclude that, under normal circumstances, foraging in M.pergandei is not water‐limited.
The effect of sublethal neogregarine infections in the spruce needleminer, Epinotia tedella (Lepidoptera: Tortricidae)
Authors: MÜNSTER‐SWENDSEN M.
Published: March 2008

Abstract.

A hitherto unknown factor causing cyclic reduction in population fertility of Epirzotia tedella (Cl.) was identified as sublethal infections of the neogregarine Mattesia sp.

Infection probably takes place when larvae enter hibernation, but does not develop into spore production until the formation of pupae and adult moths.

At the individual level, the sublethal neogregarine infection causes a slight delay in adult emergence, a decreased adult lifespan, a suppression of egg development, and thus a reduction in fertility.

At the population level, fertility reduction has a delayed density dependent component and, through correlation, Mattesia is assumed to be causative. Since fertility reduction is a key‐factor in E.tedella, Mattesia may even be a dominant factor in the dynamics of this species.

Mattesia infections were found in no other dominant insect species at the locations, and consequently the interaction between E.tedella and Mattesia sp. seems to be specific. Such delayed density dependent interaction can create host oscillations, as seen in many forest insects. However, host‐parasitoid interaction alone leads to oscillations with the observed period of 6–8 years length, and the neogregarine infections apparently act in parallel with the parasitoids and enhance the amplitude of the oscillations.
Butterfly migration from and to peninsular Florida
Authors: WALKER THOMAS J.
Published: March 2008

Abstract.

Migrating butterflies were monitored with traps for 10 years at a site in north peninsular Florida, to determine seasonal and annual variation in numbers and directions of flight.

In the spring, 81–96% of the principal migrants, Phoebis sennae (L.), Agraulis vanillae (L.), Precis coenia (Hübner) and Urbanus proteits (L.), flew northward; in the autumn, 86–95% flew southward.

Estimated mean net numbers of these four species flying northward in spring across each ENE‐WSW metre were 3, 6, 69 and <1 respectively; numbers flying southward in autumn were 222, 413, 37 and 146.

During a 5‐year period, the ratio of highest to lowest seasonal migration for a species did not exceed 9.3.

The average median date of spring migration was 27 March for P.sennae, 23 April for P.coenia, and 12 May for A.vanillae. The average median date of autumn migration was 2–5 October except for U.proteus, whose average date was 14 October.

The autumn migratory period, as measured by the duration of the middle half of migration, was about 2 weeks in P.coenia and about 4 weeks in the other three species.

Compared to previously reported butterfly migrations, the ones studied here were notably uniform in magnitude and regular in timing.

These and other data suggest that 4 million or more of these butterflies migrate northward from peninsular Florida almost every spring and that 40 million or more migrate southward to peninsular Florida almost every autumn.
Comparative nutritional ecology of bryophyte and angiosperm feeders in a sub‐Antarctic weevil species complex (Coleoptera: Curculionidae)
Authors: CRAFFORD J. E. , CHOWN S. L.
Published: March 2008

Abstract.

Highly productive and st,ructurally diverse angiosperm communities occur on sub‐Antarctic Marion Island, yet cryptogams are the main source of energy and nutrients for five of the six native weevil species (Curculionidae: Ectemnorhinini) that occur there.

Previously it has been hypothesized that low‐temperature regimes, during the Pleistocene, precluded angiosperm herbivory. This hypothesis was based,inter alia, on the assumption that at low temperatures feeding on bryophytes is more nutritionally advantageous than feeding on vascular plants.

This assumption was tested by comparing the consumption rate (CR) and approximate digestibility (AD) (mass and energy) of bryophytes and angiosperms in twoDusmoecetesspecies indigenous to Marion Island.

The approximate digestibility ofBlepharidophyllum densifolium(Scapaniaceae) energy and dry mass were similar forD.marioniJeannel adults at 5°C and at 10°C.D.similis(C. O. Waterhouse) adults fedAzorella selagoHook (Apiaceae) leaves also had similar AD for food dry mass and energy at 5°C and at 10°C. However, the performance ofD.similisonA.selagoleaves and flowers at 5°C was better than that ofD.marionion bryophytes at both temperatures.

Bryophyte feeding does not appear to be nutritionally more advantageous at low temperatures in the sub‐Antarctic, nor does angiosperm herbivory appear to be comparatively disadvantageous at low temperatures, althoughD.similisdoes not feed onAcaena magellanica(Lam.) (Rosaceae) at 5°C. It seems likely that moss‐feeding evolved in response to an absence of angiosperms during glacial periods, rather than because of a nutritional advantage associated with bryophagy at low temperatures.
Colony ergonomics for a desert‐dwelling bumblebee species (Hymenoptera: Apidae)
Authors: SHELLY TODD E. , BUCHMANN STEPHEN L. , VILLALOBOS ETHEL M. , O'ROURKE MARY K.
Published: March 2008

Abstract.

Data on worker traffic, size and concentration of nectar loads, and size and composition of pollen loads were collected for a colony of Bombus pennsylvanicus sonorus Say in the Chihuahuan Desert in Arizona, U.S.A.

Foraging activity increased through the morning to a peak level in early afternoon and then declined steadily thereafter. Pollen collection occurred primarily in the morning, whereas nectar was harvested throughout the day. Nectar loads decreased in size but increased in sugar concentration during the day.

Following field observations, we excavated the nest and counted the numbers of immatures and adults present and measured the honey and pollen reserves. A total of 150 workers were present, and we estimate that the colony would have produced 174 queens and 192 males. Food reserves appeared small: pollen and honey stored in the nest represented only 18% and 35%, respectively, of the daily input.

These results are compared to ergonomic data collected for B.vosnesenskii in the only other similar study.
Host selection and sex ratio in a heteronomous hyperparasitoid
Authors: WILLIAMS TREVOR
Published: March 2008

Abstract.

Encarsia tricolor Förster is a heteronomous hyperparasitoid: females develop as primary endoparasitoids of Homoptera, whereas males develop hyperparasitically in primary endoparasitoids, including conspecific females.

When offered pupae of Encarsia inaron (Walker) or conspecific pupae, E.tricolor showed a distinct preference to exploit E.inaron for male production.

Parasitoids were given the opportunity to gain different types of ovipositional experience on male and female hosts and were then offered patches containing mixtures of male and female hosts in various ratios. The mean sex ratio which they laid was not dependent on the relative availability of each type of host, whereas prior ovipositional experience had a significant effect.

Adaptive reasons for the observed oviposition strategies are suggested.
Species number, species abundance and body length of arboreal arthropods associated with an Australian rainforest tree
Authors: BASSET YVES , KITCHING R. L.
Published: March 2008

Abstract.

The species number, the abundance per species and the body length of arthropods foraging within the crowns of an over‐storey rainforest tree from Australia, Argyrodendron actinophyllum (Sterculiaceae), were investigated by interception trap sampling and restricted canopy fogging. Emphasis was placed upon the interpretation of trap data. Arthropods were trapped continuously day and night, over a 2‐year period and the final analyses examined the attributes of 759 species which represented 20,500 individuals.

The proportion of‘rare’species (Le. collected once) intercepted was high (35.7%), although lower than in other similar rainforest surveys. Neither the α log‐series nor the log‐normal distribution could be fitted to the relationship between number of species and number of individuals, since the number of rare species was much higher than predicted and the mode of the distribution could not be identified. The proportion of rare species was higher in fogging collections (452%) than in trap collections.

The data are compared with a study of Bornean arboreal beetles, obtained by fogging trees during a single sampling event. Several patterns were common to both data sets. However, the three‐dimensional plot of the variables describing the structure of the arthropod community showed a notably rougher surface than in the case of Bornean beetles.

Although several factors may complicate the interpretation of the three‐dimensional plots, long‐term and continuous sampling may alter our perception of complex arthropod communities. This methodology is imperative for a proper understanding of arthropod community structure in rain forests.
Mating strategy and isolation between the two forms, macrogyna and microgyna, of Myrmica ruginodis (Hym. Formicidae)
Authors: ELMES G. W.
Published: March 2008

Abstract.

It is shown that the size distribution and degree of overlap between individual queens of the two forms of Myrmica ruginodis, microgyna and macrogyna, is exactly the same in southern England as was originally described from Scotland.

Distinguishing colonies of the two forms is not as easy as distinguishing between individuals, both types can be polygynous and approximately 25% of colonies contain a mixture of queens.

Males of the two forms can be distinguished solely on the basis of size and, in general, macrogyna colonies produce larger males, workers and gynes than microgyna colonies. There is little correlation between the sizes of males, workers and gynes in colonies within the macrogyna and microgyna groups.

If the two forms are separate species and mixing is a parasitic association (as suggested elsewhere), then there should be breeding isolation between the forms. This is tested by examining data from nine mating‐swarms.

All the swarms contain a significant proportion of the microgyna form. There is no evidence of assortative mating, although larger males are more likely to get a mate than smaller ones. This behaviour, combined with the possibility that microgynes mate near to the nest, might prevent complete mixing during mating.

The status of the forms is discussed. Besides the possibility of a‘pre‐parasitic’relationship it is suggested that the forms might represent a polymorphism, present in all populations, the balance between them being the result of selection determined by local environmental factors.
The role of larval nutrition in pre‐imaginal biasing of caste in the primitively eusocial wasp Ropalidia marginata (Hymenoptera: Vespidae)
Authors: GADAGKAR RAGHAVENDRA , BHAGAVAN SEETHA , CHANDRASHEKARA K. , VINUTHA C.
Published: March 2008

Abstract.

When freshly eclosed females of the primitively eusocial wasp Ropalidia marginata (Lep.) are isolated, only about 50% of them build nests and lay eggs thereby suggesting a pre‐imaginal biasing of caste.

Wasps that lay eggs take a very variable amount of time after eclosion to start doing so.

Females eclosing from nests where larvae are fed at a relatively higher rate are more likely to become egg‐layers and are likely to take less time after eclosion to begin to lay eggs.

Thus, both forms of pre‐imaginal biasing of caste, namely, differences in egg laying capacity and differences in the time taken to attain reproductive maturity, appear to be influenced by larval nutrition.
Searching strategies and attack rates of parasitoids of the ash bark beetle (Leperisinus varius) and its relevance to biological control
Authors: MILLS N. J.
Published: March 2008

Abstract.

Point estimates of parasitoid behaviour indicated that braconid parasitoids of the bark beetle, Leperisinus varius, spend 70% of their host searching time stationary on the bark surface, in sharp contrast to the chalcidoid parasitoids which spend 60–70% of their host searching time moving across the bark surface.

Aggressive encounters between searching parasitoids are common and the data suggest that they do not occur at random.

The chalcidoid parasitoids, Cheiropachus quadrum and Eurytoma morio, are more frequently involved in aggressive encounters than expected and can displace ovipositing individuals of other species.

Attack rates for the parasitoids were estimated to vary from two hosts per day for the braconid Coeloides filiformis to four hosts per day for E.morio, and net reproductive rates vaned from 6.3 for C.filiformis to 0.8 for Coeloides melanotus.

These data suggest that while all parasitoids of the scolytid can act as primary parasitoids, at least some of the chalcidoid parasitoids are facultative cleptoparasitoids and should be avoided in classical biological control introductions.
The time and egg budget of Leptopilina clavipes, a parasitoid of larval Drosophila
Authors: DRIESSEN GERARD , HEMERIK LIA
Published: March 2008

Abstract.

For the understanding of the influence of natural selection on the persistence of host selection behaviour in populations of Drosophila parasitoids it is important to know whether parasitoids will become time‐ or egg‐limited. We investigated whether the Drosophila parasitoid Leptopilina clavipes (Hartig) meets egg‐ or time‐limited conditions in the field.

To this end the following aspects of the parasitoid's life were studied: egg load at emergence, travelling velocity between patches, patch residence times, oviposition rates and life expectancy. Together with the results from earlier studies on host and patch distributions, this formed the input of a ‘Monte Carlo’ simulation model, in which the life history of an individual parasitoid can be traced.

The simulations revealed that under the conditions found in the field 12.9% of the parasitoid population is egg‐limited. The model was also run for a number of scenarios which reflect ‘good’ or ‘bad’ circumstances. In most cases a significant proportion of the parasitoid population proved to be egg‐limited.

For the measurement of travelling velocities and patch residence times a marking method, especially applicable to small‐sized parasitoids such as L.clavipes, is described. Marking did not affect survival, host habitat location or host detection rate. Parasitoids were found to be attracted to the odour of fruit‐bodies of Phallus impudicus, the most important breeding substrate of their hosts.
To hatch or not to hatch? Egg hatch response to larval density and to larval contact in a treehole mosquito
Authors: EDGERLY JANICE S. , MARVIER MICHELLE A.
Published: March 2008

Abstract.

We investigated the effect on egg hatch of exposure to: (1) varying larval density, and (2) larval contact in Aedes triseriatus Say (Diptera: Culicidae). For 2 days in the laboratory we submerged eggs into a treehole water medium containing 0 (control), 4, 12 or 24 larvae that could either contact the eggs directly or were separated from them by a screen. Following treatment, abundance of microorganisms on the egg surfaces, a food source for newly hatched larvae and a proposed hatching stimulus, was assessed by counts made from serial dilutions of samples.

We discovered a complex hatching response to larval contact and to larval density, and an interaction between these two factors in their effect on microbial growth. Hatching was inhibited in the 0‐larva control, even though microorganisms grew abundantly on the eggs. Hatch rate, as well as microbial counts, were high for eggs in direct contact with 4 larvae. As density increased in the larval contact treatment, microorganisms disappeared from the egg surfaces and hatch rate declined.

When protected from larval grazing, eggs supported numerous microbial colonies irrespective of larval density. In contrast to the contact treatment group, egg hatch increased with increasing larval density. These observations suggest that the combination of microbial growth and a larval factor stimulates hatch. This hatching response may have evolved because both abundant microorganisms and numerous larvae reflect a habitat of good quality.
Activity pattern and thermal biology of a day‐flying hawkmoth (Macroglossum stellatarum) under Mediterranean summer conditions
Authors: HERRERA CARLOS M.
Published: March 2008

Abstract.

The daily activity pattern and aspects of the thermal biology are described for the day‐flying hawkmoth, Macroglossum stellatarum L. (Lepidoptera: Sphingidae), while foraging at a flowering population of Lavandula latifolia (Labiatae) under the dry‐hot summer conditions of a southeastern Spanish locality.

The average abundance of M.stellatarum remained fairly constant from sunrise to about 17.00 hours (GMT), and a distinct peak occurred in the evening (18.00—20.00 hours).

Foraging took place over a broad range of microclimatic conditions, as described by air temperature (Ta; range 19‐36°C) and solar radiation (IR; range 1–1025 Wm‐2).

The thoracic temperature (Tth) of insects remained within relatively narrow limits (39–46°C), with the highest values occurring around noon. Variation in Tth mainly reflected differences in Ta between foraging sites and times. Tth was nonlinearly related to Ta, the rate of increase of Tth with Ta decreasing with increasing Ta.

The unusual tolerance of high Tth exhibited by M.stellatarum, and its enhanced thermoregulatory capacity at high Ta, enable this species to withstand the severe environmental conditions faced during diurnal foraging in the Mediterranean summer.