bluuebunny/crossref_metadata_2025 huggingface dataset:
The role of extrafloral nectaries in the herbivore defence of Cassia fasiculata
Authors: BOECKLEN WILLIAM J.
Published: March 2008

Abstract. 1. An experiment is presented that tests the hypothesis that the extrafloral nectaries of Chssia fasiculata reduce herbivory by attracting pugnacious ants that deter herbivores, and tests the equivalence of two methods of ant exclusion: treatment with Tanglefoot, and nectary excision.

2. The protectionist hypothesis is not supported; treatment plants produced as many pods as did control plants.

3. Treatment with Tanglefoot is equivalent to nectary excision in terms of pod production

4. A graphical model is presented that relates the efficacy of ant protection to plant density and ant activity.
Host‐specific demographic studies of the Mediterranean fruit fly Ceratitis capitata
Authors: CAREY J. R.
Published: March 2008

Abstract. 1. This study was conducted in Greece using a wild strain of medflies (Ceratitis capitata [Weidemann]) to assess age‐specific vital rates in adults, and development and survival in pre‐adults when reared on different host fruit. The results were used to construct life tables.

2. The demographic analyses suggested that there are basically four aspects of the medfly's life history which are of major importance: (i) multiple, highlyoverlapping generations; (ii) high net reproduction while young; (iii) high larval fitness in certain hosts; (iv) lack of diapause.

3. Reasons why these characteristics are felt to be important are briefly discussed.
Organization of a parasitoid community associated with a complex of galls on Atriplex spp. in southern California
Authors: HAWKINS BRADFORD A. , GOEDEN RICHARD D.
Published: March 2008

Abstract. 1. Atriplex canescens (Pursh) Nuttall and A.polycarpa (Torrey) Watson (Chenopodiaceae) support twelve morphologically distinct gall types in southern California. Thirty‐seven common species of parasitoids, predators and inquilines are associated with these galls.

2. The galls incited by eight members of the Asphondylia atriplicis Cockerell (Diptera: Cecidomyiidae) species complex are linked into a single, interacting community through shared hymenopterous parasitoids and inquilines.

3. Cluster analysis (UPGMA) grouped the fifteen most common species of Chalcidoidea into three host guilds of five species each: (1) specialists in tumour stem and blister leaf galls on A.canescens, (2) specialists in woolly stem galls on A.poiycarpa, and (3) generalists that attack all galls. Guild 1 dominated the galls with which it was primarily associated, while guild 3 dominated the remainder.

4. The abundances of the parasitoids of the tumour stem and blister leaf galls were negatively correlated with the abundances of two organizer species, a gall‐forming inquiline, Tetrastichus cecidobroter Gordh and Hawkins, and an internal, larval—pupal parasitoid, Tetrastichus sp. B. The abundances of nine of the twelve most common chalcidoids were not correlated with the abundances of all coaccurring species in six other galls.

5. Host seasonality partly determines parasitoid population dynamics and guild structure. Parasitoid dominance increased with gall duration, suggesting that parasitoid competition depends on resource stability. The two continuously available galls were dominated by their specialist guild, while all seasonal galls were dominated by generalists. The subdominant specialists of woolly stem galls may represent competitively inferior species that utilize those galls opportunistically, because of the gall's widespread distribution and 9–10 month yearly availability.

6. Sites in the Colorado Desert and chaparral that supported several gall types showed stable relative abundances of the major parasitoid species, whereas sites in the Mojave Desert that supported only woolly stem galls had unpredictable parasitoid species assemblages.

7. The competitive success of Atriplex gall parasitoids may depend primarily on voltinism (multivoltine species dominated univoltine species) and mode of feeding (phytophagous, mixed entomophagous—phytophagous and facultatively hyperparasitic species in general dominated strict primary parasitoids).
Host relations, life cycles and multiparasitism in some parasitoids of aphidophagous Syrphidae (Diptera)
Authors: ROTHERAY GRAHAM E.
Published: March 2008

Abstract. 1. Records of parasitism from the field and host choice experiments suggest that most parasitoids of syrphids are monophagous. A few are oligophagous.

2. To elicit egg release, females require a stimulus from the host haemolymph. Differential response to haemolymph cues by females may account for the observed pattern of host relations.

3. Differences in host ranges and timing of female flight periods probably characterize most of the parasitoids studied.

4. In one case of two monophagous parasitoids, Diplazon pectoratorius (Thunberg) and Syrphophilus tricinctorius (Thunberg) attacking the same host Syrphus ribesii (L.) no partitioning was found. Stricinctorius is, however, a superior intrinsic competitor.
Why does the hoverfly Metasyrphus corollae migrate?
Authors: SVENSSON BO G. , JANZON LARS‐ÅKE
Published: March 2008

Abstract. 1. Migration pattern and mass appearance of the hoverfly Metasyrphus corollae (F.) (Diptera, Syrphidae) were investigated on the SE coast of Sweden in 1981. In total, 4433 hoverflies, belonging to fifteen species, were collected in water traps during 4–6 August. All but 2.2% were M.corollae, 3282 specimens being caught on 4 August, 1021 on 5 August and thirty‐five on 6 August.

2. The sex ratios (♂/♀) on these dates were 1/1.6, 1/1.3 and 1/1.7. The average dry weights did not significantly differ between sexes (males 4.01 mg, females 4.02 mg).

3. M.corollae females were reproductively immature.

4. Females mostly had Senecio pollen in their guts while males mainly had Rubus pollen. The average number of pollen grains per specimen was 210 for females and 1100 for males.

5. In the summer 1980 aphids were numerous, forming a basis for a high abundance of adult hoverflies (with hibernating larvae) in 1981. Aphid density in 1981 was low and stimuli inducing egglaying were sparse. It is suggested that this pattern of aphid abundance triggers migration in M.corollae and in other aphidophagous species at irregular intervals.
Fitness of two sibling species of Asobara (Braconidae:Alysiinae), larval parasitoids of Drosophilidae in different microhabitats
Authors: VET LOUISE E. M. , JANSE CHRIS J.
Published: March 2008

Abstract. 1. Two sibling species of larval endoparasitoids of Drosophilidae: Asobara tabida (Nees) and A.rufescens (Foerster) occur in the same macrohabitat, but inhabit different microhabitats. Each species is most attracted by odours of its own microhabitat.

2. In order to assess the adaptive value of the microhabitat preference we studied the survival of both parasitoids in the major host species that occur in these microhabitats.

3. Survival in the major host in the preferred microhabitat was shown to be 40% higher for A.tabida and 30% higher for A.rufescens when compared to survival in the major host in the non‐preferred microhabitat.

4. Measurements of developmental rates, specific mortalities and dry weights of the parasitoids suggest that the differential survival is due to differences in synchronization with the hosts.

5. The possible evolutionary consequences of some biological characteristics in Asobara are discussed. Microhabitat selection, differential survival, development and mating behaviour are attributes likely to have played a role in the reduction of gene flow between populations of the ancestral species, either in primary or in secondary sympatry.
Contrasting movement patterns of nectar‐collecting and pollen‐collecting bumble bees (Bombus terricola) on fireweed (Chamaenerion angustifolium) inflorescences
Authors: GALEN C. , PLOWRIGHT R. C.
Published: March 2008

Abstract. 1. Movements of nectar and pollen‐foraging bumble bees on inflorescences of Chamaenerion angustifolium (L.) J. Holub (fireweed or rosebay willow herb) were compared with predictions based on reward distributions and optimality principles. Observations suggest that nectar and pollen‐gathering bumble bees behave according to the same set of reward maximization criteria when foraging from flowers of this species.

2. Both kinds of foragers matched their arrival points with the vertical positions on inflorescences in which the densities of their respective food resources were greatest. For nectar‐foragers, this point was located at the lowest tier of flowers, whereas for pollen‐foragers it was found in the middle of the inflorescences. Nectar and pollen‐foraging bees both moved upward on inflorescences following gradients from high to low reward availability.

3. Nectar‐foragers responded to decreases in inflorescence size over the season by reducing the number of flower visits made on each raceme. Number of flowers visited by pollen‐foragers was low throughout and reflected the scarcity of male‐phase flowers on racemes. Flower revisitation rates were low for both kinds of workers, but were slightly higher for those collecting pollen.
Bracken, ants and extrafloral nectaries. III. How insect herbivores avoid ant predation
Authors: HEADS P. A. , LAWTON J. H.
Published: March 2008

Abstract. 1. Ants (Myrmica spp. and Formica lemani) visiting the extrafloral nectaries of bracken, Pteridium aquilinum, imposed heavy mortality on caterpillars of a novel moth species experimentally introduced onto bracken fronds. However, the exclusion of ants from bracken fronds had no significant effect on adapted bracken‐feeding herbivores in Britain.

2. The feeding stages of British bracken‐feeding insects are immune to, or can largely avoid, predation by ants in a variety of ways. Gall formers and miners cannot be attacked by these ants. Two other species hide, one inside tied leaves, the other in a mass of ‘spittle’. Another group of species jumps away from, or falls off the plant when touched by ants. Sawfly caterpillars in the genera Strongylogaster, Aneugmenus and Tenthredo have viscous, distasteful haemolymph that repels ants.

3. No species of bracken herbivore has an absolute temporal refuge from ants; during their development they all overlap with ants to some degree.

4. Ant predation appears to have played a significant role in determining the contemporary structure of British bracken‐feeding insect communities. Distasteful haemolymph in sawfly caterpillars may have evolved in response to selection from ant predation. Other species may fortuitously possess characteristics, evolved in response to a variety of selective forces, that also reduce the impact of ants; without such characteristics, however, we postulate that they would be unable to live on this plant. An absence of external, foliage feeding Lepidoptera early in the spring, a high proportion of sawfly species, and a high proportion of gall‐formers and miners may all be characteristics of the bracken herbivore community which have been influenced by ant predation.
Ecological strategies of Dalbulus leafhoppers
Authors: NAULT L. R. , MADDEN L. V.
Published: March 2008

Abstract. 1. Developmental times from egg to adult eclosion were established for eight Dalbulus leafhopper species on maize (Zea mays) and its perennial, gamagrass relative, Tripsacum dactyloides. Experiments were conducted with a 16 h day (25–27°C) and an 8 h night (21–22°C).

2. Developmental times were shortest for the maize specialists, c. 26 days for D. maidis and c. 27 days for D. elimatus, and longest for the Tripsacum specialists, c. 32 days for D. tripsacoides, c. 34 days for D. quinquenotatus and c. 40 days for D. guzmani. Developmental times were intermediate for D. gelbus, D. longulus and D. guevarai, species that utilize both maize and Tripsacum as field hosts.

3. For all species, development was significantly faster on maize (species mean 29 days) than on T. dactyloides (species mean 34 days).

4. D. maidis and D. elimatus developed significantly faster (c. 3 days) on maize than on its close perennial relative, Z. diploperennis.

5. As measured by a 48 h oviposition period, D. maidis, D. elimatus and D. gelbus produced significantly more progeny on maize than on gamagrass. D. quinquenotatus produced more progeny on T. dactyloides than on maize. D. maidis and D. elimatus produced more progeny on maize than on Z. diploperennis.

6. These studies provide support for the hypothesis which predicts that herbivorous insects that specialize on annual plants will have a shorter generation time and be more fecund than perennial specialists. The genus Dalbulus appears to be composed of species that fit an r‐K continuum, with maize specialists and Tripsacum specialists at opposite ends of the continuum.
The function of multiple anti‐predator mechanisms in adult tiger beetles (Coleoptera: Cicindelidae)
Authors: PEARSON DAVID L.
Published: March 2008

Abstract. 1. Predator avoidance mechanisms of adult tiger beetles (Cicindela spp.) were investigated in the Sulphur Springs Valley of southeastern Arizona, U.S.A.

2. The predators were found to be robber flies, lizards, and birds.

3. Effective antipredator characters included body size, orange abdomens, defence chemicals, flight and gregariousness.

4. The number of these five major antipredator mechanisms exhibited by each tiger beetle species varied with habitat.

5. The function and number of antipredator mechanisms was a complex interaction of deterrents; some were effective only in combination and some were characters that each deterred a different type of predator; in several cases, the characters that reduced the probability of attack by one type of predator simultaneously increased the probability of attack by another type of predator.
Effects of leaf toughness on mandibular wear of the leaf beetle, Plagiodera versicolora
Authors: RAUPP MICHAEL J.
Published: March 2008

Abstract. 1. The effects of leaf toughness on mandibular wear of the leaf beetle Plagiodera versicolora Laich. (Coleoptera: Chrysomelidae) were evaluated by feeding adult beetles young (tender) and old (tough) leaves of Salix babylonica and S. alba ‘Tristis’.

2. Tough leaves erode the cutting surface of beetle jaws more so than tender leaves.

3. Beetles with worn jaws consumed leaves at a slower rate than ones with less mandibular wear.

4. Because rates of leaf consumption and egg production are positively correlated, increased mandibular wear may reduce beetle fecundity.

5. These results support the belief that leaf toughness may act as a potent defence affecting morphology, feeding behaviour, and ultimately spatial and temporal patterns of herbivores.
Seasonal changes in the response of wood‐ants (Formica lugubris) to sucrose baits
Authors: SUDD J. H. , SUDD M. E.
Published: March 2008

Abstract. 1. The acceptability of sucrose solutions to Formica lugubris Zett. in the field was tested by offering droplets of known concentrations to ants tending aphids.

2. A probit model fitted to the data allowed the computation of the Median Effective Concentration (ED50) and its confidence limits.

3. In spring and early summer ED50 was about 0.15 M sucrose, but the ED50 rose in 1 week at the end of June from 0.2 M to 0.9 M. The change was simultaneous on pine and birch trees. The ED50 fell gradually to about 0.4 M in early November.

4. The increase in ED50 is related to the production of the summer apterae in the aphids tended, Cinara pini (L.) on pines and Symydobius oblongus (von Heyden) on birch. This increases the ‘quality’ of food resource so that low sucrose concentrations can no longer compete for ant attendance.

5. The increase in ED50 may limit the attendance of wood‐ants at the nectaries of bracken, Pteridium aquilinum (L.) Kuhn. and at colonies of some other aphid species which are attended only in early summer.
Phenological relationships of wasps, bumblebees, their mimics and insectivorous birs in northern Michigan
Authors: WALDBAUER G. P. , LaBERGE W. E.
Published: March 2008

Abstract. 1. In northern Michigan 72% of the high fidelity dipterous Batesian mimics of bumblebees and vespoid wasps occurred in spring while they still outnumbered their models but before the great majority of fledgling birds left their nests to begin foraging for insects on their own.

2. This extends the known occurrence of this sort of phenology to several additional mimetic species and to an area which is radically different climatically and ecologically from the central Illinois areas in which this sort of phenology was first noted.

3. Our observations confirm the hypothesis that Batesian mimics may be selected to avoid the midsummer period when newly fledged insectivorous birds are abundant but have not yet learned to shun their stinging hymenopteran models.

4. The shortness of the warm season in Michigan reduces opportunities for temporal separation and may have forced the other 28% of the high fidelity mimics to occur when naive birds are abundant. The threat from naive birds was, however, presumably somewhat ameliorated by the abundance of models at that time.
Factors underlying the late seasonal appearance of the lepidopterous leaf‐mining guild on oak
Authors: WEST C.
Published: March 2008

Abstract. 1. Most lepidopterous leaf mining species found on the oak Quercus robur in Britain develop in summer. At this time of year, externally feeding caterpillars remove little leaf area since most of these free living folivores are predominantly spring feeders.

2. I forced Phyllonorycter harrisella (L.) miners to oviposit in spring, then exposed developing larvae to a wide range of leaf damage levels.

3. Leaf miner survivorship and mean female pupal weight were significantly greater in the experimental spring generation on undamaged oak leaves, this being when oak foliage is of the highest nutritional quality.

4. Leaf miner survivorship in all generations is correlated with natural leaf damage levels. Experimental leaf damage also reduces miner survivorship.

5. Leaf damage reduces miner survivorship by increasing the probability of larval death due to wound induced responses.

6. The role of asymmetrical competitive interactions between caterpillars and leaf‐miners in determining the late seasonal appearance of miners is discussed. It is suggested that wound induced responses may play an important part in the structuring of phytophagous insect communities.
Patterns of intra‐ and interspecific association in leaf‐mining insects on three oak host species
Authors: BULTMAN THOMAS L. , FAETH STANLEY H.
Published: March 2008

Abstract. 1. We determined mortality and distributional patterns of leaf miners on three oak host species (Quercus falcata, Q.nigra and Q.hemisphaerica) in northern Florida, U.S.A.

2. Patterns of intra‐ and interspecific occurrence within leaves, and mortality of five most abundant leaf miner species were analysed as a test of competition.

3. Miners co‐occurred on leaves more often that expected by chance (P<0.05) in six of ten possible species combinations and log‐linear model analysis showed no negative higher‐order interactions.

4. All five miner species had highly clumped distributions between leaves (P<0.01).

5. Leaf miner survival was less than expected for four of five species when co‐occurring on leaves with conspecifics than when mining with heterospecifics or alone (P<0.05).

6. We conclude that interspecific competition is unapparent within this leaf miner guild and that intraspecific competition occurs in four of the five major leaf miner species. We discuss leaf miner selection of common leaves, perhaps based on chemical/physical leaf characters, as a cause of intra‐ and interspecific aggregation.
The foraging ecology of the army ant Eciton rapax: an ergonomic enigma?
Authors: BURTON JAMES L. , FRANKS NIGEL R.
Published: March 2008

Abstract. 1. The army ant Eciton rapax (F. Smith) produces longer raid systems than any other member of its genus and it is a specialist predator of forest floor and understory ants such as species of Camponotus, Odontomachus and Pachycondyla.

2. Allometrical analysis confirms that E. rapax is the only member of its genus without distinct physical castes among its workers: its foraging population is entirely monomorphic and there are no majors.

3. The workers of E. rapax are distributed over a considerable size range, and there are distinct divisions of labour within these colonies: small workers tend to stay in the nests and among the larger foraging workers those retrieving prey items are significantly bigger than the rest.

4. An analysis of foraging efficiency and worker performance in E. rapax suggests that transport costs, resulting from the great distances that workers travel during raids and emigrations, are one of the selection pressures that have favoured the evolution of large monomorphic workers in this species.
Foraging by the carabid Agonum dorsale in the field
Authors: GRIFFITHS E. , WRATTEN S. D. , VICKERMAN G. P.
Published: March 2008

Abstract. 1. Small arenas in the field were used for observing adult Agonum dorsale (Pont.) foraging in a wheat crop.

2. The carabid showed no significant change in behaviour between low and high aphid density arenas.

3. Individuals foraged nocturnally and spent most of their time on the ground searching for prey. They climbed infrequently and then not high enough to reach aphid aggregations on the ears and flag leaves of wheat.

4. Gut dissection showed that more individuals had eaten aphids in the high aphid density arena than the low. Recording of aphid distribution within the arenas showed that this increase in aphid consumption could be explained by A.dorsale capturing aphids on the ground. Prey availability per unit area was in fact higher on the ground than on the wheat.

5. The contribution of ground‐zone predators such as A.dorsale to the control of cereal aphids will be determined by the frequency with which aphids arrive on the ground and the proportion of these which reclimb the wheat and reproduce in the absence of predation.
Insect visitors to extrafloral nectaries of Byttneria aculeata (Sterculiaceae): relative importance and roles
Authors: HESPENHEIDE HENRY A.
Published: March 2008

Abstract. 1. Ants, parasitoids and flies are about equally frequent at foliar nectaries of Byttneria aculeata (Sterculiaceae) in lowland Costa Rica during the dry season, a pattern previously unreported but also observed at other plants in the area.

2. Species of Ectatomma, Crematogaster and Camponotus were the most frequent of twenty‐four ant species on Byttneria, eight of which nested in the hollow stems. Ants spent most time at nectaries and little in patrolling.

3. Collections at nectaries yielded large numbers of species of parasitoid Hymenoptera with few individuals of each. Rearing studies of leaf‐feeding herbivores yielded several species of parasitoids, including one species taken at a nectary and two others congeneric or closely related.

4. Flies appear to be nectar thieves, in the same sense as non‐pollinating floral visitors, despite close association with Byttneria.

5. Ant‐plants may be poor models for the larger number of species of less specialized plants with extrafloral nectaries. Plants which have only extrafloral nectaries may better suit the needs of parasitoids than ants, and plants such as Byttneria may benefit as much from parasitoids as from ants.
Determining the age of adult male and female Glossina morsitans morsitans using a new technique
Authors: LEHANE M. J. , MAIL T. S.
Published: March 2008

Abstract. 1. Pteridines accumulated linearly with age up to at least 63 days in male and 140 days in female Glossina morsitans morsitans Westwood kept under laboratory conditions. Time is the major factor influencing total pteridine accumulation levels with the accumulation rate being modulated by temperature.

2. It is suggested that pteridine accumulation may be used to determine the age of male and female tsetse flies in the field.
Ability of ovipositing seed beetles to discriminate between seeds with differing egg loads
Authors: MESSINA FRANK J. , RENWICK J. A. A.
Published: March 2008

Abstract. 1. Previous work has shown that ovipositing females of Callosobruchus maculatus (F.) avoid seeds already bearing eggs, and thereby reduce competition among their larval progeny within seeds.

2. This study demonstrates that females also detect small differences in egg density, and prefer to oviposit on seeds with a lower‐than‐average number of eggs. A nearly uniform dispersion of eggs is thus maintained even after all seeds bear several eggs.

3. In addition, variation in egg load influences oviposition rate. Transfer of females from seeds with few eggs to seeds with many eggs inhibits oviposition; the reverse transfer stimulates it.

4. The upper surface of the egg chorion or egg ‘cover’ remains intact on the seed surface after the larva has entered the seed and continues to deter egg‐laying for at least as long as the period required for larval development. 14‐day‐old egg covers provide as much deterrence as freshly laid eggs.
The relationship between size and reproductive potential in male and female Epirrita autumnata (Lep., Geometridae)
Authors: HAUKIOJA ERKKI , NEUVONEN SEPPO
Published: March 2008

Abstract. 1. We studied the fecundity of Epirrita autumnata Bkh. (Lepidoptera) in relation to pupal weight of females and males.

2. There was no clear correlation between male size and the success in fertilization over a considerable range of weights (from 50 mg to over 100 mg) although in one experiment only large males were successful in multiple fertilizations.

3. In the three experiments where small males (<50 mg) were used they showed reduced performance, and a large proportion of them was sterile.

4. Unlike in males, the number of eggs laid by females correlated linearly with pupal weight over the whole range of female weights.
Activity patterns, diets and interspecific interactions of coexisting spring and autumn breeding carabids: Carabusyaconinus and Leptocarabus kumagaii (Coleoptera, Carabidae)
Authors: SOTA TEIJI
Published: March 2008

Abstract. 1. Activity patterns, diets and interspecific interactions of two coexisting carabid beetles, Carabus yaconinus B. and Leptocarabus kumagaii K. et K., were studied in a lowland habitat in Japan.

2. Larvae of C. yaconinus appeared from May to October and fed on earthworms. Those of L. kumagaii appeared from October to the next May and fed on dipteran and lepidopteran larvae.

3. In the adult stages, feeding habits and daily activities of the two species were similar. The beetles fed mainly on earthworms and other animal materials, but various plant materials were also utilized.

4. Direct competition for food items was observed both intra‐ and interspecifically. Interspecific interactions occurred only in early summer, however, because of the difference in breeding seasons (i.e. spring for C. yaconinus and autumn for L. kumagaii).

5. The difference in seasonal life history patterns between these carabids is a possible mechanism of coexistence.
Host gall size and oviposition success by the parasitoid Eurytoma gigantea
Authors: WEIS ARTHUR E. , ABRAHAMSON WARREN G. , McCREA KENNETH D.
Published: March 2008

Abstract. 1. Eurytoma gigantea Walsh is a specialist parasitoid of the tephritid gallmaker Eurosta solidaginis (Fitch).

2. In the natural environment the incidence of parasitism by Eurytoma is greater in small galls than in large ones.

3. Laboratory experiments demonstrated that small galls are not more frequently discovered; however, oviposition attempts on small galls were more likely to be successful.

4. Eurytoma spends much time probing galls too big to penetrate; this leads to a decrease in foraging efficiency when many large galls are present.

5. The chance of successfully penetrating a gall depends on the thickness of the gall wall and the length of the parasitoid's ovipositor.

6. A simulation model was constructed which shows that a gallmak‐er's chance of being parasitized depends on gall size, the number of parasitoids that discover the gall, and their ovipositor lengths.
Diurnal activity patterns in hoverflies (Diptera, Syrphidae)
Authors: GILBERT FRANCIS S.
Published: March 2008

Abstract. 1. Time‐budgets are constructed from censuses of hoverflies. Larger species spend less time in flight.

2. Most species are active under similar conditions of light intensity, but a shade‐tolerant (Melanostoma scalare Fabr.) and a sun‐loving species (Metasyrphus corollae Fabr.) were identified.

3. Large species become active (i.e. move, by flying or feeding) at lower temperatures than small ones, except M.scalare, which is tolerant to cool temperatures. This means that, M.scalare apart, the order of species appearing during the day is size‐dependent, largest first.

4. Previous claims about the diel periodicity of syrphids can be reconciled by considering the importance of individual thermal balance.

5. Tolerance to low temperatures in small hoverflies is associated with feeding on anemophilous pollen; this may indicate a proline‐fuelled flight.
The predatory Chironomidae of an iron‐rich stream: feeding ecology and food web structure
Authors: HILDREW ALAN G. , TOWNSEND COLIN R. , HASHAM AZIM
Published: March 2008

Abstract. 1. Three species of Tanypodinae (Chironomidae) were found in an acid and iron‐rich stream in southern England. Maximum abundance was achieved in summer and they were sparse at other times. Individuals were aggregated on the stream bed and were overrepresented in accumulations of leaf litter.

2. The diets of all three species consisted of a mixture of prey (prominently detritivorous chironomid larvae) and detritus. More detritus and fewer prey were taken in winter than in summer.

3. When comparing large tanypod species with small and, intraspecifically, late instars with early, the proportion of guts containing prey increased with increasing body size.

4. Stonefly larvae were more prominent in the diet of Zavrelimyia barbatipes (Kieffer) in summer than in winter but for the other two species the reverse was true. A bigger proportion of Trissopelopia longimana (Staeger) guts contained prey in early summer than in August whereas more Macropelopia goetghebueri (Kieffer) guts contained prey in August. This was apparently a consequence of seasonal differences in the distribution of body size among the populations of these two species.

5. The stream contains two further common predators, Plectrocnemia conspersa (Curtis) and Sialis fuliginosa Pict. These are important predators of tanypod larvae but might also compete with them since they severely deplete populations of prey taken in common.

6. Analysis of the food‐web in Broadstone Stream reveals remarkably high values of connectance (C and Cmax) and of species richness times connectance (SCmax). Such characteristics are theoretically associated with fragile and dynamically unstable food webs, and may be found in ‘constant’ environments. There is also an apparently unusual prevalence of omnivory in the community.
Mechanical limitations on feeding by meadow spittlebugs Philaenus spumarius (Homoptera: Cercopidae) on wild and cultivated host plants
Authors: HOFFMAN GEORGED. , McEVOY PETER B.
Published: March 2008

Abstract. 1. Field observations on the distribution of Philaenus spumarius (L.) on pearly everlasting (Anaphalis margaritacea) and alfalfa (Medicago sativa) showed that the range of feeding sites exploited increased with instar. Development of trichomes, depth of xylem elements, and tissue hardness were measured as possible factors determining the suitability of sites on food plants.

2. Spittlebugs caged outside their normal feeding sites experienced difficulty feeding. Experimental removal of trichomes showed that trichomes prevented younger instars from feeding on the stem. The depth of the xylem elements and tissue hardness were not significant barriers to feeding near the stem apex.

3. By caging fourth and fifth instar nymphs at increasing distances below the terminal bud on A.margaritacea stems, we showed feeding ability declined with distance below the apex, and feeding was more restricted in fourth compared to fifth instars. A similar decline was demonstrated in experiments with fifth instars on M.sativa.

4. On A.margaritacea, this restriction was associated with increasing tissue hardness of the stem with distance from the apex and the presence of trichomes in regions with hard tissues. On M.sativa the associated barriers were a combination of tissue hardness and reduction in the availability of xylem vessels in the penetrable region of the stem. Although the tissues impeding stylet penetration differed in the two hosts, the critical factor in both species was the increase in the amount of lignification of those tissues at increasing distances from the terminal bud.
An association between two species of pine aphid, Schizolachnus pineti and Eulachnus agilis
Authors: KIDD N. A. C. , LEWIS G. B. , HOWELL C. A.
Published: March 2008

Abstract. 1. Two aphid species feed exclusively on pine needles, Schizolachnus pineti (Fabr.) occupying only the outer (curved) surface with Eulachnus agilis (Kalt.) showing a preference for the inner (flat) surface.

2. Despite E.agilis favouring and S.pineti avoiding senescing needles, both species show a significant tendency to share shoots and needles in the field.

3. The same association is also apparent under laboratory conditions, although E.agilis is randomly distributed between needles in the absence of S.pineti.

4. E.agilis was found to benefit through increased survival and faster growth rates, by feeding on the same shoots and needles as S.pineti.

5. It is suggested that E.agilis may be able to detect and exploit an improvement in the nutritive quality of needles brought about by the feeding activity of S.pineti colonies.
Aggregation and mating of thrips in flowers of Calystegia sepium
Authors: KIRK WILLIAM D. J.
Published: March 2008

Abstract. 1. Aggregation and mating of Thrips major Uzel and Thrips fuscipennis Haliday (Thysanoptera: Thripidae) in the 1‐day flowers of Calystegia sepium (L.) R.Br. are described.

2. The number of thrips per flower increased rapidly after flower‐opening at dawn and decreased during the evening and following morning.

3. Males patrolled the corolla, attempting to copulate with any females that landed. Their movement was affected by the density of thrips on the corolla. Most females were among the stamens and style, apparently feeding on pollen.

4. These thrips were also abundant in flowers of Filipendula ulmaria (L.) Maxim. They fed on pollen, and grains adhered to them. They may be significant pollinators because of their high frequency of flights.

5. The aggregations appear to be a simple consequence of general flower‐finding responses to colour and scent that are particularly elicited by flowers of C.sepium and F.ulmaria. The ecological significance of male aggregations is discussed.
Size effects on the hygrothermal balance and foraging patterns of a sphecid wasp, Cerceris arenaria
Authors: WILLMER P. G.
Published: March 2008

Abstract. 1. Cerceris arenaria (L.) females nest in sandy burrows, foraging for prey weevils to stock cells in which eggs are laid. Nests are easily distinguished and observed, and tunnel diameter correlates well with the occupying females' size (range 68–128 mg).

2. Foraging depends on ambient temperature and occurs only during periods of insolation. Large females can forage earlier in the day, and usually make a greater number of successful trips per day, than smaller ones.

3. Size differences of females affect heat exchange and resultant temperature excesses (Tex). At the highest ambient temperatures Tex for the largest wasps can exceed physiological tolerances, thus reducing foraging activity relative to the smaller females.

4. On very hot days wasps forage more frequently for nectar, probably to reduce their water deficits. Larval water balance is controlled less directly, by the architecture of burrows and the nature of cell walls and contents.

5. Temperature effects on foraging and nesting bring about a roughly two‐fold increase in success as cell provisioners (and hence egg‐layers) of larger over smaller females. Possible countering effects of very hot weather and of parasitism, either of which might favour small females in some conditions, are discussed.
Changes in life‐cycle strategies of Carabus problematicus over a range of altitudes in Northern England
Authors: BUTTERFIELD J. E. L.
Published: March 2008

ABSTRACT.

Mandible tip length has been used to estimate the age of individual C.problematicus Herbst caught over an altitude range of more than 700 m in northern England.

At 100 m the great majority of females laid eggs in the summer of their emergence as adults. The female life‐cycle is predominantly annual and 24% only of the egg‐bearing individuals were in their second year.

Above 250 m, most females did not reproduce until the summer of the year following emergence, giving a biennial life‐cycle. 96% of egg‐bearing females caught above 830 m were in their second year.

All the males caught during the breeding season at 100 m had emerged within that calendar year and it is concluded that the male life‐cycle is annual at this altitude.

Above 250 m, 83% of the males caught during the breeding season were in their first calendar year, suggesting that recently emerged males may inseminate second year females and also that the male life‐cycle is predominantly annual over the whole altitude range studied.

At the higher temperatures of the lowland site females not only produce eggs in the year of emergence, they also produce more eggs per individual than at the higher sites. Egg production depends on food intake which involves mandible wear and individuals at the lowland site have significantly higher rate of mandible wear than at the sites above 250 m.
Alarm‐recruitment behaviour in Pheidole militicida (Hymenoptera: Formicidae)
Authors: FEENER DONALD H.
Published: March 2008

ABSTRACT.

Pheidole militicida Wheeler, a seed‐harvesting species of the southwestern United States, possesses a major worker caste (soldiers) with unusually large heads. Previous work suggested that these large major workers are specialized defenders against large seed‐harvesting species in the genus Pogonomyrmex.

Experimental introductions of Pogonomyrmex maricopa Wheeler and the omnivorous fire ant, Solenopsis xyloni McCook, demonstrate that P. militicida colonies alarm‐recruit major workers against S.xyloni workers but not against the larger Pogonomyrmex workers.

P.militicida is the second species in which enemy‐specific defence against Solenopsis fire ants has been detected. I suggest that the special role of Solenopsis as both competitor and predator in ant communities frequently favours major worker specialization against this genus.

Major workers of P.militicida and Pheidole dentata Mayr, the other species with enemy‐specific defence against Solenopsis, are morphologically very different from one another. It is suggested that interspecific variation in major worker morphology is not necessarily associated with variation in behavioural specialization.
The effects of foraging ants on arboreal insect herbivores in an undisturbed woodland savanna
Authors: GRANT S. , MORAN V. C.
Published: March 2008

ABSTRACT.

A comparison was made of the insect fauna on paired Terminalia sericea, Burkea africana and Ochna pulchra trees; one tree in each pair was treated with Formex® to exclude ants from the canopy, and the other was designated the control.

Treatment with Formex banding to exclude ants did not influence plant phenology.

Pyrethrum knockdown samples from control trees had generally more insect individuals and insect species than samples from trees where ants were excluded.

Formex‐treated trees had significantly less homopterous individuals and species than the control trees.

With the exception of ants and Homoptera, there was no difference in the insect guild composition and dominance ranking of various insect taxa, sampled by pyrethrum knockdown, between the control and Formex‐treated trees.

T.sericea had significantly greater populations of both sessile and mobile Homoptera on the control trees than on the Formex‐treated trees. A similar trend could be seen on B.africana. There were significantly more sessile homopterans on the control trees of O.pulchra than on the Formex‐treated trees. Low numbers of mobile Homoptera were recorded on both control and Formex‐treated O.pulchra trees, and numbers on control trees were fewer in comparison to numbers of mobile Homoptera on control T.sericea and B.africana trees.

It is concluded that the ants have similar effects on the insect communities of trees in a natural, undisturbed savanna as has been demonstrated on trees in agro‐ecosystems, and on plants that are structurally adapted for mutualistic associations with ants.

Although slight, leaf damage by some leaf‐feeding insects was greater on trees where ants had been excluded than on control trees that supported foraging ant populations.
Local population differences in emergence of cabbage root flies from south‐west Lancashire: implications for pest forecasting and population divergence
Authors: FINCH STANLEY , COLLIER ROSEMARY H. , SKINNER GARETH
Published: March 2008

ABSTRACT.

Emergence of cabbage root fly, Delia radicum (L.), from overwintering populations of puparia collected from twenty‐one sites in south‐west Lancashire, was extremely variable.

The patterns of emergence indicated that there were two extreme biotypes, one with early‐ and the other with late‐emerging flies. There was also evidence of an intermediate biotype, tending more to early than to late emergence.

This gradient of biotypes, or clinal divergence, was maintained by populations breeding at different times and by females mating close to their sites of emergence. Non‐dispersive females then perpetuated their genotype within their own locality.

The time of emergence was not obviously associated with the type of host‐crop on which larvae had developed.

The late‐emerging biotype was most prevalent around Halsall. The minimum distance between populations of the late‐ and the early‐emerging biotypes was 16 km. 20 km south‐east from Halsall only half of the fly population was early‐emerging, possibly a result of a displacement of the Halsall biotype by the prevailing NW wind.

Regional‐based forecasts will need to take into account the emergence characteristics of the populations to predict the peak periods of cabbage root fly activity adequately in south‐west Lancashire and other areas where emergence patterns differ.
The natural diet of the Notonectidae: field trials using electrophoresis
Authors: GILLER P. S.
Published: March 2008

ABSTRACT.

Field trials were conducted on populations of two sympatic species of the waterbug Notonecta (Hemiptera: Heteroptera), to examine their natural diet using the electrophoretic method of gut contents analysis.

Fingerprint esterase bands were identified from thirty‐three potential aquatic prey types; gut contents of different instars of both species of Notonecta from the field were analysed.

The level of prey identification possible ranged from 73% in fifth instar N.glauca L. to 100% in third instar N.viridis Delcourt.

Type A errors, where no prey remains were detected from a full gut, were found in only 3% of the specimens analysed.

Data on gut states, the number of prey types per gut and details of aquatic prey found in the diet of different instars of field‐collected Notonecta are presented.

These results are compared with previous data on notonectid diets, and the relative merits of different methods of diet analysis are discussed.
Behavioural response of spider mites (Tetranychus urticae) to induced resistance of cotton plants
Authors: HARRISON SUSAN , KARBAN RICHARD
Published: March 2008

ABSTRACT.

Spider mites (Tetranychus urticae Koch) given a choice between a cotton plant previously damaged by mites and an undamaged control preferentially moved to the control plant.

This host‐choice behaviour was seen in adult female mites but not in immatures.

Adult females were not found to be significantly more fecund on control plants than on previously damaged plants, but the duration of this choice experiment precluded full assessment of effects on fecundity.

Mites responded very quickly, choosing previously undamaged plants without contacting or feeding on the test plants. This suggests that an olfactory response to a chemical substance(s) is involved.
Behavioural and ecological adaptations to the high mountain environment of Polistes biglumis bimaculatus
Authors: LORENZI M. C. , TURILLAZZI S.
Published: March 2008

ABSTRACT.

Polistes biglumis bimaculatus (G. in Furcroy) (Hymenoptera: Vespidae), a high mountain species, was studied in the Alps. Adaptations of this species to the severe climate and reduced nesting season include nesting characteristics, social organization and division of labour, and caste succession.

Foundress association occurs only in the late pre‐emergence period and is not the same as that seen in low altitude species.

The foundress females continue to forage even in the post‐emergence period and workers and reproductive (males and females) emerge almost contemporaneously.
The use of discriminant analysis for the estimation of sampling biases for female tsetse
Authors: RANDOLPH SARAH E. , ROGERS DAVID J.
Published: March 2008

ABSTRACT.

In this paper we investigate whether the technique of discriminant analysis can be used to estimate sampling biases for female tsetse.

Discriminant analysis was first applied to laboratory samples of female tsetse, Glossina morshans morsitans Westwood, to test whether flies of known history could be assigned to the correct day of the pregnancy cycle on the basis of their fat, haematin and corrected residual dry weight.

Following the satisfactory results from the laboratory samples, the same technique was applied to field samples of G.m. centralis Machado captured by electric traps and hand nets in Zambia and of G.palpalis palpalis (Robineau‐Desvoidy) captured in biconical traps at five sites in Ivory Coast. The results show that flies on day 1 of the pregnancy cycle were most likely to be caught, with a second peak of day‐6 and day‐7 flies, while very few day‐8 or day‐9 flies were caught.

These major peaks in fly trappability coincide with the known feeding habits of female tsetse, and indicate synchrony of feeding by many members of the population immediately after larviposition and again as the larva in utero moults from the second to third instar. G.palpalis is relatively more available at this later stage of its pregnancy cycle to the capture methods used than is G.morsitans. A third feed may be taken at a more variable point in the pregnancy cycle.

This method of estimating the sampling biases of female tsetse could allow an estimate of total population size, as long as the absolute sampling efficiency of flies on any one day of the pregnancy cycle could be established by, for example, mark‐release‐recapture experiments.
Skeletal economy in certain herbivorous beetles as an adaptation to a poor dietary supply of nitrogen
Authors: REES CHRISTOPHER J. C.
Published: March 2008

ABSTRACT.

Flying Coleoptera were sampled with light traps from the tree canopy of lowland alluvial rain forest in Brunei, Borneo.

Adult chrysomelid beetles were found to carry significantly less skeleton relative to their overall mass than those of any family other than herbivorous scarabaeids (subfamily: Rutelinae). Xylophagous lucanids and cerambycids and dung‐feeding scarabaeids (subfamilies: Aphodiinae and Scarabaeinae) carried as large a proportion of skeleton by mass as predatory carabids and cicindelids.

Skeletal production requires the commitment of assimilated nitrogen to chitin and proteins. Adequate nitrogen is more readily available to predators, carrion or dung‐feeders, and xylophages (given enough time) than to leaf‐chewing chrysomelids, which are also environmentally exposed to predatory attack. Female chrysomelids were found to carry a larger number of mature eggs/insect than those of any other family. A larger proportion of their mass was represented by eggs than skeleton, as reproductive compensation for reduced skeletal protection.

It was estimated that a chrysomelid beetle required approximately 43% of the nitrogen incorporated by a predatory carabid of the same mass, whereas xylophagous cerambycids and lucanids would need between 84% and 98% of that in the predator.