bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct and indirect effects of a predatory backswimmer (Notonecta maculata) on community structure of desert temporary pools
Authors: BLAUSTEIN LEON , KOTLER BURT P. , WARD DAVID 
Published: March 2008

Abstract.

We assessed experimentally the effects of the predatory backswimmer, Notonecta maculata, on naturally colonizing mosquito populations in artificial outdoor pools in the Negev Desert, Israel. A single Notonecta adult per pool (8–15 litres water) had a very large negative impact on populations of Culiseta longiareolata, the most common species found in natural local pools. Notonecta caused large reductions of Culiseta egg rafts and early‐instar larvae (instars I and II) and virtually 100% reductions of late‐instar Culiseta larvae (instars III and IV) and pupae.
Notonecta also caused a trophic cascade in the experimental pools; by preying on periphyton‐feeding Culiseta larvae, Notonecta indirectly caused significantly higher densities of diatoms, the major component of the periphyton.
Surveys of nearby natural pools taken between March and May supported the experimental results: a strong negative association between Notonecta and Culiseta among pools occurred as Notonecta increased in numbers and became more widely distributed. Anopheles (occurring only in May) and Culex mosquito immatures were not negatively associated with Notonecta. Culiseta was not associated with surface vegetation whereas both Culex and Anopheles showed strong positive associations with surface vegetation both among and within pools. We attribute the negative association between the predator and Culiseta to local prey extinctions caused by Notonecta in individual pools. Culiseta, being an open water species, is apparently more prone to predation by Notonecta than the vegetation‐dwelling Culex and Anopheles.
Potential rates of Increase of solitarious and gregarious phases of the African armyworm Spodoptera exempta (Lepidoptera: Noctuidae)
Authors: CHEKE ROBERT A. 
Published: March 2008

Abstract.

The African armyworm Spodoptera exempta exhibits a phase polyphenism with insects capable of transforming from one‘phase’to another, which involves both physiological and behavioural changes. Amongst these changes, evidence from the laboratory and the field suggest that, given equivalent conditions of temperature and food, solitary phase insects take longer to complete their life cycles than gregarious phase insects, and the latter's generations are more synchronized. There is also some evidence that females of the solitary form sometimes lay more eggs.
Using data from field and laboratory studies, estimates of the rates of increase of each form were calculated from Leslie matrix models. Assuming equivalent mortality rates for both phases, asynchronous development for the solitaries and synchronous development for the gregarious forms, with the latter having lower fecundities than the solitaries, the models suggest that the gregarious forms have higher values of their intrinsic rates of increase (r) than solitarious populations. These results are explored using a range of parameter values including variation in the percentage of solitaries with delayed development.
The possible ecological and evolutionary significance of variations in rates of increase of gregarious and solitary populations are briefly discussed.
Interspecific host discrimination and competition inApoanagyrus (Epidinocarsis) lopeziandA.(E.)diversicornis, parasitoids of the cassava mealybugPhenacoccus manihoti
Authors: PIJLS JANINE W. A. M. , HOFKER KEES D. , STAALDUINEN MARTIN J. VAN , ALPHEN JACQUES J. M. VAN 
Published: March 2008

Abstract.Choice experiments on interspecific host discrimination inA.lopeziandA. diversicorniswere carried out on discs of cassava leaf containing four hosts (P.manihoti) that had been parasitized by the other species and four unparasitized hosts.A.lopeziaccepted both host types equally for oviposition, whereasA.diversicornisaccepted fewer hosts that had been parasitized byA.lopezithan unparasitized ones.A.diversicornisis therefore capable of interspecific host discrimination, but such a capability was not demonstrated forA.lopezi.Survival probability in singly parasitized hosts was 0.85 for both parasitoid species. When the time interval between ovipositions was 2 h or less, survival in multiparasitized hosts was 0.68 forA.lopeziand 0.17 forA.diversicornis, irrespective of priority. IncreasingA.lopezipriority to 24±2h did not increaseA.lopezisurvival.A.diversicornissurvival, however, increased to 0.43 whenA.diversicorniswas given 24 ± 2 h priority.A.diversicorniseggs took 19 h longer thanA.lopezieggs to hatch. This could explain the difference in competitive abilities in multiparasitized hosts.The observed difference in host selection behaviour betweenA.lopeziandA.diversicornisis in accordance with the different benefits of multiparasitism:A.lopezigains more thanA.diversicornisbecause of its superior within‐host competitive abilities.Neither species avoided multiparasitism completely. The low survival probability ofA.diversicornisin multiparasitized hosts may partly explain its failure to establish when introduced into Africa as part of a biological control programme ofP.manihoti.
Diapause, migration and pyrethroid‐resistance dynamics in the cotton bollworm, HeIicoverpa armigera (Lepidoptera: Noctuidae)
Authors: SOUZA KENNETH DE , HOLT JOHNSON , COLVIN JOHN 
Published: March 2008

Abstract.

A diapause induction and duration experiment was conducted in the laboratory on Indian Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) where 79% of individuals had extended pupal periods. At 22°C and 26°C respectively, 57% and 100% of the pupae had emerged 145 days after pupation.
A mathematical model was developed to investigate the interactions between diapause, migration and pyrethroid resistance frequency development in both eastern Australia and Andhra Pradesh, India.
The effect of diapause was different in the Australian and Indian cases, providing a mechanism to conserve resistance and susceptibility respectively.
For Australia, the model simulated discriminating dose data reasonably well and showed that resistance frequencies could rise prior to the pyrethroid window without invoking cross‐resistance to non‐pyrethroid insecticides applied to cotton.
The saw‐toothed seasonal cycle of resistance development could be simulated in the Indian case without hypothesizing the existence of susceptible migrants.
The implications of‘refugia’populations for H.armigera insecticide resistance management programmes are discussed.
Structural refuges in two stem‐boring weevils onRumex crispus
Authors: FREESE GUNTER 
Published: March 2008

Abstract.Differences in feeding positions, parasitoid complexes and parasitization rates of the two dominant insect species in stems ofRumex crispuswere investigated.Apion miniatum(inhabiting the lower 10% of the stem) andApion violaceum(occurring all along the stem) exploited distinctly different feeding positions, partly due to differences in time of oviposition.A.miniatumsuffered less parasitization thanA.violaceum, measured both by number of parasitoid species and parasitization rates. Its feeding position constitutes a refuge.Parasitization ofA.violaceumwas least in individuals feeding in basal, thick parts of the stem. There is a trend that the developed refuge increases with increasing stem diameter.The refuge ofA.violaceumin basal positions only affected idiobiont ectoparasitoids, because koinobiont endoparasitoids attack the weevils before they enter the stem. Moreover, the koinobiont did benefit from the refuge itself by avoiding hyperparasitism.Densities ofA.violaceumincreased with plant size, whereas percentage parasitism did not differ. Its three most abundant parasitoid species showed small‐scale density‐independent patterns of attack over all plants. Therefore a constant proportion of weevil larvae mine within the refuge independent of its potential size.Synchronization between weevils and plants, as well as between parasitoids and hosts, appears to be the dominant factor for the spatial community structure of the stem borersof Rumex crispusand their enemies.
The influence of diet on growth and secretion behaviour of myrmecophilous Polyommatus icarus caterpillars (Lepidoptera: Lycaenidae)
Authors: BURGHARDT FRANK , FIEDLER KONRAD 
Published: March 2008

Abstract.

Caterpillars of the facultatively myrmecophilous butterfly Polyommatus icarus were reared on inflorescences, or foliage, of four natural hostplant species and on an artificial diet to study dietary effects on larval growth and secretory capacity.
Caterpillars achieved highest weights and relative growth rates when fed flowers of Medicago sativa, Lotus corniculatus or Melilotus officinalis. Larvae reared on Coroniüa varia (flowers and leaves), foliage of M.sativa and on the artificial diet pupated at lower weights and achieved lower growth rates.
In standardized experiments with the ant species Lasius flavus, secretion rates from the dorsal nectar organ (DNO) were 2 times higher among flower‐fed caterpillars than among foliage‐fed siblings or caterpillars on the artificial diet. Larvae reared on C.varia flowers were superior to all other food treatments with respect to secretion rates.
High water content of larval diet, as in flowers, appears to be important for lycaenid caterpillars to achieve high secretion rates, whereas the correlation between myrmecophily and nutrient availability, as evidenced by growth rates, was less pronounced.
Using experimental data on larval growth and secretion rates, the lifetime volume of secretions from the DNO is estimated to range from 2 to 5 μl in most food treatments. Only on C.varia flowers (5.5–8.7 μl) and on M.sativa leaves (0.9–1.1 μl) did the caterpillars deviate in their absolute investment in myrmecophily.
The estimated lifetime investment accounted for 1.6–5.5% of prepupal fresh weight in all food treatments except on C.varia flowers (7.8–12.3%).
Carabid life‐cycle strategies and climate change: a study on an altitude transect
Authors: BUTTERFIELD J. 
Published: March 2008

Abstract.

There was little overlap in the species composition of carabid beetle assemblages sampled below 450 m and above 800 m on an altitude transect and the first axis of a DECORANA ordination was closely correlated with altitude (r11= 0.93, P < 0.001), probably reflecting the differing temperature requirements of different species.
Life‐cycle strategies of two low‐altitude species, found predominantly below 600 m, and two species caught above 600 m a.s.l., have been determined, using mandible wear to identify whether the females breed in the calendar year that they emerge as adults or in the year following.
Nebria salina has an annual cycle at 630 m. Pterostichus madidus and Calathus fuscipes were both biennial at altitudes above 300 m although predominantly annual at low altitude. N.gyllenhali was biennial above 600 m and it is not known whether it is able to switch to an annual cycle at low altitude.
Both N.salina and N.gyllenhali ceased activity soon after emergence, an adaptation which preserves their mandibles from wear.
At altitudes of 305 m and 430 m, P.madidus and C.fuscipes entered the breeding season with 33% and 56% reduction in mandible tip length, possibly reducing their reproductive output.
The necessity for relatively sharp mandibles on entry into the breeding season may restrict the capacity of carabids to respond to a temperature change by switching from annual to biennial cycles, and vice versa, adding support to the suggestion that carabids are more likely to respond to climate change by shifting distributions than by physiological adaptation.
Temporal changes in host adaptation in the pea aphid, Acyrthosiphon pisum
Authors: SANDSTRÖM JONAS 
Published: March 2008

Abstract.

Temporal changes in host adaptation were followed in a local population of the pea aphid, Acyrthosiphon pisum. Aphid clones were collected in one alfalfa and one clover field at three different times. In the spring, first‐generation females were collected. Later, in the autumn, females belonging to the last parthenogenetic generation were collected. Lastly, sexual females were collected after mating in autumn and allowed to produce eggs which were hatched. The performance was evaluated on alfalfa and clover. The spring‐collected individuals were also assessed on peas.
On the overwintering hosts clover and alfalfa, the clones performed best on the plant of origin, i.e. negative correlations in performance. Correlations between performance on the temporary summer host, pea, and that on clover/alfalfa were weak or nonsignificant.
Significant variation in host performance was found within both host fields at spring, which is a prerequisite for changes in clone composition due to selection/migration.
The clones from alfalfa showed an increase in mean performance on alfalfa between spring and autumn, whereas no changes among the clones from the clover field were observed. This difference in seasonal response between the two fields could have been the result of larger variation in performance among the alfalfa clones and/or a differential tendency to migrate among clones in both fields.
After sexual recombination in the autumn, mean performance in the alfalfa field returned to the spring level, probably as a result of emergence of new genetic combinations. In the clover field, mean performance did not change significantly over time.
The window of vulnerability and its effect on relative parasitoid abundance
Authors: BRIGGS CHERYL J. , LATTO JOHN 
Published: March 2008

Summary.1. The length of time that a gall‐forming midge,Rhopalomyia califomica, was vulnerable to attack by four parasitoid species was measured in the field at two locations.2. The midge had a restricted window of vulnerability to each of the parasitoid species, but similar windows of vulnerability were found at the two sites.3. A stage‐structured model was used to illustrate that the length of the vulnerable window should have no effect on the fraction parasitized by a single parasitoid species if that species is the only parasitoid attacking the host in a coupled host‐parasitoid interaction. However, the length of the window of vulnerability can have a positive effect on the fraction parasitized by a species in competition with other parasitoid species.4. The length of the window of vulnerability can help explain the relative field abundance of four of the common parasitoid species ofR.californica.
Movement of an insect parasitoid in simple and diverse plant assemblages
Authors: COLL MOSHE , BOTTRELL DALE G. 
Published: March 2008

Abstract. 1. It has been proposed that herbivore populations are lower in diverse than in simple plant habitats because of greater abundance and/or higher efficiency of natural enemies in mixed plant stands. However, higher enemy colonization is expected in monorather than multispecific vegetation if the response of specialist natural enemies to habitat diversification is similar to that of monophagous herbivores.2. We used release‐recapture experiments to determine how the presence of maize (non‐host plant) influences the movement of the parasitoid Pediobius foveolatus in the absence of hosts. We then assessed how vegetation diversity affects wasp reproduction (parasitism) and subsequent density in the presence of its hosts, Mexican bean beetle larvae.3. Fewer female wasps immigrated into and more emigrated out of a bean‐tall maize intercrop than bean monocultures. Bean plant density and the presence of maize per se did not significantly affect parasitoid immigration. Instead, maize height was the primary factor contributing to lower female immigration into the bean‐tall maize plots. However, tall maize plants did not impede the wasps' within‐habitat movement.4. When wasps were released outside the plots, higher parasitism was recorded in monocultures, irrespective of host density. In contrast, when wasps were released within the plots, significantly higher parasitism rates were found in the bean‐tall maize habitat.5. Results suggest that female wasps accumulate in the bean‐tall maize habitat in response to resources other than hosts and, ultimately, wasp density may be determined primarily by differential emigration rather than by immigration rates.
Impact of a natural enemy overwintering refuge and its interaction with the surrounding landscape
Authors: CORBETT ANDREW , ROSENHEIM JAY A. 
Published: March 2008

Abstract1. Egg parasitoids in the genus Anagrus (Hymenoptera: Mymaridae) are important mortality factors for grape leafhoppers (Erythroneura elegantula; Homoptera: Cicadellidae) in California vineyards, yet must overwinter in habitats external to these vineyards. Existing evidence suggests that French prune trees, which harbour the overwintering host Edwardsiana prunicola, planted adjacent to vineyards may enhance early‐season abundance of Anagrus.2. Anagrus overwintering in French prune tree refuges were labelled with the trace element rubidium in four separate experiments. Rubidium‐labelled Anagrus were captured in adjacent vineyards in two of the experiments, confirming that French prune trees contribute to early‐season Anagrus populations. Anagrus from refuges were captured at the most distant sampling positions, 100 m from refuges.3. Use of rare element labelling has, for the first time, enabled the relative contribution of different sources to early‐season colonization by this parasitoid to be quantified. Refuges contributed 1% and 34% of Anagrus colonizing two of the experimental vineyards, respectively. The remainder originated from overwintering habitats external to the French prune/vineyard system.4. The spatial patterns of Anagrus originating from external overwintering habitats suggest that the French prune trees are generating a ‘windbreak effect’. Anagrus dispersing within the windstream colonized vineyards at a higher‐than‐average rate immediately downwind of refuges.5. The amount of colonization by Anagrus from external overwintering habitats was apparently related to the distance to presumed overwintering habitats. These findings demonstrate that both the number of natural enemies emerging from a refuge and the composition of the surrounding landscape are important in determining the impact of local, small‐scale habitat manipulations.
Post‐emergence migration of stoneflies (Plecoptera) into the nearby forest
Authors: KUUSELA KALEVI , HUUSKO ARI 
Published: March 2008

Abstract. 1. The post‐emergence lateral migration of both sexes of eight stonefly species was examined in a dystrophic, fourth‐order forest river in eastern Finland.2. For this purpose, 7351 stonefly adults were collected with eighteen trunk funnels positioned in rows of six at distances of approximately 1, 15 and 60 m from the river. A further 1880 adults were also caught from the vegetation of the bank zone by sweep netting and with slit traps.3. The species could be grouped into two types with respect to migration distance: Isoperla difformis, I.grammatica and Leuctra fusca tended to stay in the bank area, whereas Nemoura flexuosa, N.avicularis, Amphinemura borealis, L.hippopus and N.cinerea tended to disperse into the forest, so that the majority were found some distance away from the shore.4. The males of the leuctrids, N.flexuosa and N.cinerea migrated farther than the females.5. The sex ratio was significantly biased in all species except N.flexuosa. The isoperlids, leuctrids and A.borealis showed a significant predominance of females in the trunk funnel catches, but males were significantly dominant in N.avicularis and N.cinerea. The material caught by other methods reversed the ratio for I.difformis and N.avicularis. Comparison of the sex ratios of the species with other reports revealed marked variation and deviation from unity, much of which could be attributed to bias introduced by the sampling methods.6. Lateral migration seems to be the first phase in the colonization cycle, although the latter as such was not studied here. Adults of Euholognatha species migrate farther than those of Systellognatha, a difference of which may be due to their ability to feed as adults.
Reproductive mechanisms and dynamics of habitat colonization inMicrocerotermes biroi(Isoptera: Termitidae)
Authors: LEPONCE M. , ROISIN Y. , PASTEELS J. M. 
Published: March 2008

Abstract.1. Previous studies on the arboreal termite community in coconut plantations of northern New Guinea showed thatMicrocerotermes biroiis the most abundant species, despite the fighting superiority of two competitor speciesNasutitermes princepsandN.novarumhebridarum.In this study we tested the hypothesis that the success ofM.biroiis due to its efficiency at colonizing new habitats following nuptial flights.2. We demonstrated experimentally the ability ofM.biroicolonies to replace their reproductives when removed, or to produce reproductives in satellite nests when isolated from the remainder of the colony. Replacement reproductives were always neotenics, derived from nymphs or workers.3. Despite the ability of neotenics to differentiate within their home colonies, 84% of field colonies were headed by dealated imagos. This value constitutes a minimum estimate of the proportion of field colonies founded independently by imagos after the nuptial flight.4. The monitoring of a young plantation during the first 31/2 years of its colonization by arboreal nesting termites revealed its invasion byM.biroi, which colonized 63% of the trees while neitherNasutitermesspecies appeared.5. Our results demonstrate thatM.biroiis actually a pioneer species, able to invade a new habitat by means of nuptial flights. They outline the importance of each species' reproductive strategy in shaping the arboreal‐nesting termite community.
Mating systems and sexual division of foraging effort affect puddling behaviour by butterflies
Authors: SCULLEY COLLEEN E. , BOGGS CAROL L. 
Published: March 2008

Abstract. 1. Foraging effort can vary among age classes and between the sexes. In many Lepidoptera, young males feed from mud, dung or carrion in a behaviour known as ‘puddling’, whereas females rarely puddle. In at least one species, males transfer sodium gained from puddling to females at mating for use in egg production.2. Here we examine sex‐ and age‐specific puddling patterns in seven montane butterfly species. We also test the hypothesis that among species in which young males predominate at puddles, differences in age‐ and sex‐specific puddling patterns for a given species are related to mean female lifetime mating numbers.3. For five species, young males fed proportionately more at puddles than other sex and age classes. Two species showed anomalous feeding patterns. In one, young females predominated at puddles; in the other, butterflies were rarely found at flowers.4. As predicted, among the five species in which young males feed proportionately more at puddles, mean number of lifetime matings by females was negatively correlated with frequency of mud puddling by older females. A second prediction that mean number of lifetime matings by females is positively correlated with frequency of mud puddling by older males was not supported.5. The results provide support for interspecific variation in division of responsibility between the sexes for resource acquisition for female reproduction, indicating close coordination between the sexes of foraging and life‐history tactics.