bluuebunny/crossref_metadata_2025 huggingface dataset:
Leaf shape and the host‐finding behaviour of two ovipositing monophagous butterfly species
Authors: MACKAY D. A. , JONES R. E.
Published: March 2008

Abstract. 1. Ovipositing Eurema brigitta (Wallace) and Eurema herla (W. S. Macleay) butterflies were followed in the field to determine the nature and extent of the pre‐alighting discrimination shown by these insects towards their only host plant, Cassia mimosoides (L).

2. Both species tended to search in areas where plants with long, thin leaves (primarily grasses) were less common, on average, than in randomly placed quadrats. Both species were also more likely to alight on non‐host plants with leaves of a similar size and shape to those of the host plant than on non‐hosts with leaf shapes dissimilar to that of the host.

3. The search behaviour of these monophagous insects was not so specialized that the butterflies never alighted on non‐hosts; in fact the majority of alightings were on non‐host plants and the pre‐alighting discrimination shown by these insects is clearly not the prime behavioural determinant of their monophagy.
Seasonal emergence, host‐seeking activity, age composition and reproductive biology of the mosquito Aedes punctor
Authors: PACKER M. J. , CORBET PHILIP S.
Published: March 2008

Abstract. 1. Seasonal patterns of adult emergence, host‐seeking and reproductive ageing in a population of the woodland mosquito Aedes punctor (Kirby) are described from field studies in northern Britain in 1984 and 1985.

2. The pattern of emergence showed little variation between years but duration did vary. Males started emerging before females. Sex ratios at emergence showed a marked female bias. A late, second period of emergence apparently represented a second generation in this normally univoltine species.

3. Host‐seeking females were first caught at human bait within a few days of the start of emergence and peak numbers at bait occurred 3–4 weeks later. High numbers lasted for c. 2 weeks. The duration of host‐seeking activity was related to weather. The second emergence in 1985 resulted in a second peak of activity in early September and probably extended the flight season.

4. As the season progressed the proportion of females that were parous increased. However, this proportion never reached 1.0, indicating variation in individual reproductive success, which differed between years.

5. The reproductive biology of individuals within the population was investigated. No autogeny was detected, suggesting that the population was entirely anautogenous.
The timing of oviposition and larval growth by two tephritid fly species in relation to host‐plant development
Authors: STRAW N. A.
Published: March 2008

Abstract. 1. The relationships between the timing of oviposition, larval establishment and host development were studied in the tephritids Tephritis bardanae (Schrank) and Cerajocera tussilaginis (Fab.) which attack flowerheads of Arctium minus (Hill) Bernh. (Compositae).

2. T. bardanae laid eggs in small sized flowerheads that were at an early stage of development, and appeared to use the external dimensions of the head as an oviposition cue. In contrast, C. tussilaginis females laid eggs into heads that were near to flowering and the timing of their attack was most closely related to particular lengths of florets and achenes inside the head. Both tephritids apparently recognized suitable heads by comparing aspects of their own body size with the size of particular flowerhead structures.

3. Individual heads were suitable for oviposition for a period of 10–11 days for both species, but the periods of susceptibility to each species did not overlap.

4. Attack by T. bardanae was timed to exploit the flowering phase of flowerhead development. Larval establishment and early development were synchronized with increasing nutrient availability occurring during the rapid growth of the florets and achenes before and during anthesis.

5. In contrast, the later attack by C. tussilaginis was timed to exploit the seed maturation phase of head development. Individual C. tussilaginis larvae operated as highly specialized ‘achene parasites’, utilizing the influx of nutrients into single achenes after fertilization.

6. Larvae of both tephritids induced abnormal host‐tissue growth, but oviposition in both species was timed primarily to synchronize larval development with natural periods of high nutrient availability inside flowerheads, rather than with the presence of tissues suitable for gall induction.
Interspecific differences among swallowtail larvae (Lepidoptera: Papilionidae) in susceptibility to aristolochic acids and berberine
Authors: MILLER JAMES S. , FEENY PAUL P.
Published: March 2008

Abstract. 1. The larvae of four swallowtail butterfly species, Papilio polyxenes Fabr. in the Papilionini, Parides bunichus (Hübner) and Battus polydamas (L.) in the Troidini, and Eurytides marcellus (Cramer) in the Graphiini, were grown on host leaves to which test compounds had been added.

2. The test chemicals are biosynthetically related. Berberine, a 1‐benzyl‐tetrahydroisoquinoline‐related (1‐BTIQ) alkaloid, is found in many rutaceous hosts of the Papilionini; laudanosine, a simpler 1‐BTIQ alkaloid, is found in the Papaveraceae, plants on which no papilionids feed; aristolochic acids are found only in the Aristolochiaceae, hosts of the Troidini.

3. Swallowtail larvae can tolerate the compounds characteristic of their host plants, but not chemicals found in the hosts of other papilionid groups. Diets with laudanosine did not affect the test species.

4. Our results support the contention that plant secondary chemicals, such as berberine and aristolochic acids, are important feeding barriers, and are partially responsible for host specificity in swallowtails.
Dispersal of the thistle gallfly Urophora cardui and its endoparasitoid Eurytoma serraiulae (Hymenoptera: Eurytomidae)
Authors: SCHLUMPRECHT HELMUT
Published: March 2008

Abstract. 1. The dispersal of the gall‐forming tephritid Urophora cardui L. (Diptera: Tephritidae) and its endoparasitoid Eurytoma serratulae Latr. (Hymenoptera: Eurytomidae) from an experimental colony were investigated over a period of 4 years.

2. The dispersal rate for both fly and endoparasitoid was one to two magnitudes higher than in previous studies, which found 100 m per generation maximally. The dispersal rate of the endoparasitoid was not less than that of its host. Most newly founded colonies were small and had high extinction rates.

3. The viability of colonies of U. cardui did not correlate with the distance from the dispersal centre.

4. The dispersal rates observed are high enough to allow a multiple spread and extinction in mid‐Europe in the post‐pleistocene period.
Reduced pesticide inputs on cereal field margins: the effects on butterfly abundance
Authors: DOVER JOHN , SOTHERTON NICOLAS , GOBBETT KAY
Published: March 2008

Abstract. 1. On a study farm in Hampshire where large blocks of cereal fields had the pesticide inputs on their headlands experimentally and selectively reduced (the practice known as ‘conservation headlands’), numbers of butterflies were monitored over 4 years by using transect counts.

2. Consistently more butterflies were seen flying over field edges sprayed under the conservation headland regime compared to those that were fully sprayed.

3. A comparison of changes in butterfly abundance on the study farm containing conservation headlands with data from the National Butterfly Monitoring Scheme indicated that population increases in some species may result from the use of conservation headlands.

4. The implications of resource provisioning and the potential reduction of spray drift into field‐margin habitats are discussed in relation to farmland butterflies.
Host plant variation in mortality of the leaf‐folding sawfly on the arroyo willow
Authors: FRITZ ROBERT S. , NOBEL JENNIFER
Published: March 2008

Abstract. 1. We tested the hypothesis that survival and sources of mortality of the leaf‐folding sawfly (Phyllocolpa sp.) varied significantly among host plants of the arroyo willow (Salix lasiolepis Bent ham).

2. Survival of the leaf folder differed among field and potted willows in a common environment in two of three cases, and sources of mortality differed among plants in four of five cases.

3. Egg mortality differed among field plants but not among the potted willow plants.

4. Larval mortality and parasitism differed among field and potted willows in 2 years, and appeared to be compensatory mortality sources.

5. Leaf folder density among plants was not generally correlated with percentage of leaf folds with no egg (galls formed but no subsequent oviposition), percentage survival, or percentage mortality, indicating a general lack of density dependence.

6. The proportion of folds with no egg oviposited differed significantly among field and potted plants, and was only correlated with survival or sources of mortality in one of three years.

7. The data support the hypothesis that host plant genotype affects the interaction of the leaf folder with its natural enemies, and thus represents a three trophic level interaction.
Asymmetric intraspecific competition among larvae of the damselfly Ischnura elegans (Zygoptera: Coenagrionidae)
Authors: GRIBBIN SIMON D. , THOMPSON DAVID J.
Published: March 2008

Abstract. 1. A laboratory competition experiment is described in which the growth and development rates of larvae of the damselfly Ischnura elegans (Lind.) were measured over an entire instar.

2. Two larval instars which commonly occur together in the field were used in the experiment; they were maintained with a superabundance of prey and either larvae from the same or the larger/smaller instar.

3. Small larvae suffered increased development times and decreased size increases at the moult in the presence of large larvae but similar interference effects were not evident when these smaller larvae were in the presence of other small larvae.

4. Development time and size increases of large larvae were not significantly affected by the presence of small larvae.

5. Irrespective of the instar combinations investigated, interference effects were reduced when there were more perches available, although in only a few cases was this reduction significant.

6. The consequences of the asymmetric competition reported in the experiment for the study of lifetime reproductive success in damselflies are discussed. Late emerging adults may incur reduced reproductive success.
The effects of group size and host species on development and survivorship of a gregarious caterpillar Halisidota caryae (Lepidoptera: Arctiidae)
Authors: LAWRENCE W. S.
Published: March 2008

Abstract. 1. The effect on growth and survivorship of the number of Halisidota caryae (Harris) caterpillars in groups feeding on three taxonomically distinct hosts was examined experimentally in the field.

2. Caterpillars grew more rapidly and survived better in larger sized groups than in smaller sized groups.

3. Caterpilliars grew more rapidly and survived better on Carya ovata (Koch) than on Hamamelis virginiana (L) or Quercus velutina (Lam.).

4. There were equal numbers of invertebrate predators on groups of different sizes and thus larger groups had significantly fewer predators per caterpillar than did smaller groups.

5. Invertebrate predators accounted for at least a 10% daily decrease in survivorship.

6. Local movement reduced predation because moving groups had fewer predators than did stationary groups.
Seasonal dynamics, movements and the effects of experimentally increased female densities on a population of imaginal Calopteryx aequabilis (Odonata: Calopterygidae)
Authors: CONRAD K. F. , HERMAN T. B.
Published: March 2008

Abstract. 1. A population of Calopteryx aequabilis Say was sampled daily on a tributary of Canard River, Kings County, Nova Scotia, for the entire flight season in 1983 (29 May to 13 August), using capture–mark–recapture techniques.

2. 2701 sightings of 678 individuals were obtained along a 635 m segment of the stream. A maximum daily count of 174 imagines was reached on 11 June, after which the population gradually declined.

3. More females than males were marked but sexually mature males outnumbered females at the water on all but four days.

4. Immigration rather than local emergence accounted for a large proportion of the population after 20 June.

5. Females were consistently vagile; males were site–specific but occasionally moved long distances between captures.

6. Males and females first marked as tenerals became reproductively mature after about 5 days.

7. We experimentally increased female density on a partially isolated section of the study stream to see how increased female numbers affected the demographics and movement patterns of the population.

8. Residence times for introduced and resident females were similar. In contrast, during a similar introduction of males a year earlier, most introduced males disappeared quickly.

9. Males decreased the distance they travelled daily between captures, their total distance travelled and their range following the introduction, and females showed a tendency (not statistically significant) toward increased movements and dispersal, as predicted.
Correlated traits for migration in the Gerridae (Hemiptera, Heteroptera): a field test
Authors: FAIRBAIRN D. J. , BUTLER T. C.
Published: March 2008

Abstract. 1. The hypothesis that the migratory tendency of macropters is correlated with proportion macropterous in wing‐polymorphic insects is tested by comparing the migration of macropters of three species of waterstriders (Heteroptera, Gerridae) under natural conditions.

2. Migration of marked individuals among four permanent and seventeen ephemeral water bodies was recorded between 1 April 1986 and 2 June 1987, within an area of approximately 2 km2.

3. The proportion of macropters migrating was significantly lower for G.buenoi Kirkaldy than for L.dissortis Drake and Harris and G.comatus Drake and Hottes. Similar results were obtained in. comparisons of proportions captured on ephemeral sites.

4. Distances measured in this study appear to be small relative to the migratory capacity of all of the species, and migration distance did not differ significantly among species. All species migrated primarily in early spring, and differences among species were most apparent at this time.

5. The observed differences among species combined with the results of a similar study of macropters from the primarily apterous species, G.remigis Say, support the initial hypothesis. The implications of this for our understanding of the evolution and maintenance of wing polymorphisms are discussed.
Do caterpillars disperse their damage?: larval foraging behaviour of two specialist herbivores, Euphydryas phaeton (Nymphalidae) and Pieris rapae (Pieridae)
Authors: MAURICIO RODNEY , BOWERS M. DEANE
Published: March 2008

Abstract. 1. To examine ecological and evolutionary aspects of caterpillar foraging behaviour, this study focused on observation of the individual foraging behaviour of two lepidopteran species,Pieris rapae L. andEuphydryas phaeton (Drury), on their respective host plants.

2. Periodic observations over the course of a day showed that the larvae move considerable distances, forage on the upper surfaces of leaves, and often immediately leave areas from which they have fed, leaving a pattern of dispersed herbivory.

3. Differences in foraging behaviour were not found between the two species, even though one species is aposematic and the other is cryptically coloured, but there were significant differences in the foraging patterns of P.rapae on the two host plants, broccoli and radish.
Cardiac glycosides and oviposition by Danaus plexippus on Asclepias fruticosa in south‐east Queensland (Australia), with notes on the effect of plant nitrogen content
Authors: OYEYELE S. O. , ZALUCKI M. P.
Published: March 2008

Abstract. 1. Previous studies which attempt to relate oviposition by female monarchs, Danaus plexippus (L.), to the cardiac glycosides of their milkweed host plants are reviewed and found to be defective.

2. Here we followed ovipositing females in the field and recorded their oviposition behaviour on individual Asclepias fruticosa (L.) plants. The cardenolide glycoside and per cent nitrogen of each of these plants and also of a control set of plants was recorded.

3. Milkweeds accepted by females, on which egg laying took place, had significantly lower mean cardenolide levels compared with rejected plants and a control sets of plants.

4. Most oviposition (c. 70%) took place on plants with intermediate cardenolide (CG) levels (=200–300 μg/0.1 g DW).

5. The mean CG level in A.fruticosa was 345 μg/0.1 g DW (SD = 138, n=122, range 119–719).

6. There was no relationship between monarch oviposition behaviour and plant per cent nitrogen.
Microhabitat use and hindwing phenotype in Hipparchia semele (Lepidoptera, Satyrinae): thermoregulation and background matching
Authors: SHREEVE T. G.
Published: March 2008

Abstract. 1. Microhabitat use and background matching by adult Hipparchia semele (L.) in a coastal sand dune site in south Wales were studied during the flight period of 1986.

2. Microhabitat use by both sexes is related to temperature and activity. When settling substrates are cool, typically during the early morning, most individuals are located on the warmest basking substrate, lichen patches. After a period of warming, males perch to locate mates on exposed areas of sand where there is a large field of view and where they are visually apparent. Egg‐laying females tend to settle on lichen patches throughout the day.

3. Overall, females are maximally visually cryptic when settled on lichen patches with unexposed forewings. Male crypsis on lichen is less effective, but greater on most other substrates, than that of females. It is argued that individuals match lichen patches because this substrate is used when they are most liable to detection and capture by vertebrate predators. Male crypsis is probably a compromise between maximizing protection on lichen patches and requirements for resemblance to other substrates.

4. The underside hindwing phenotype does not match sand. Background matching to this substrate is probably not important because it tends to be used when individuals are active and can effectively use secondary defence mechanisms.

5. It is suggested that the apical eyespot and orange patch on the forewing underside have a dual role in secondary defence, acting as a startling and deflective device, being exposed by disturbed individuals and by those engaged in activities which may disrupt the visual crypsis afforded by the hindwing underside.
Host specificity and seasonal distribution of Alloxysta pleuralis, a cynipoid hyperparasitoid of aphids in India
Authors: SINGH RAJENDRA , SRIVASTAVA PARAS NATH
Published: March 2008

Abstract. 1. Alloxysta pleuralis (Cameron) is a cynipoid (Hymenoptera) hyperparasitoid of aphids (Homoptera) through their aphidiid (Hymenoptera) parasitoids.

2. It was recorded attacking five aphidiids, Lysiphlebus delhiensis (Subba Rao & Sharma), Trioxys indicus Subba Rao & Sharma, Aphidius uzbekistanicus Luzhetzki, Lipolexis scutellaris Mackauer and Lysiphlebia mirzai Shuja‐Uddin (in order of preference) out of eight species of aphidiid parasitoids tested.

3. Percentage of hyperparasitism of aphids infesting cucurbits, cereals and pulses is higher than in solanaceous crops. Maximum hyperparasitism was recorded on the T. indicus/Aphis gossypii Glover/cucurbit complex.

4. The aphid host as well as the food plants significantly influence its efficiency.

5. A.pleuralis is abundant in northeastern Uttar Pradesh in winter (December–March) when large areas of pulses, cereals and cucurbits are infested with aphids serving as hosts for the primary parasitoids.
Oviposition by Danaus plexippus in relation to cardenolide content of three Asclepias species in the southeastern U.S.A.
Authors: ZALUCKI M. P. , BROWER L. P. , MALCOLM S. B.
Published: March 2008

Abstract. 1. Female monarchs were observed in the field ovipositing on a native North American milkweek host, Asclepias humistrata L. As in a comparable Australian study on an introduced novel host (Asclepias fruticosa L.) we found post‐alighting rejection of plants with low and high cardiac glycoside concentration (CG).

2. Most oviposition took place on plants with CG in the range 200–500 μg/0.1 g dry weight. Thin‐layer chromatography showed no obvious qualitative difference in cardenolide types between accepted and rejected plants, excepting an indication that rejected plants may have a higher level of more polar cardenolides.

3. In a controlled laboratory experiment comparing oviposition on a low (A.incarnata L.) vs high (A.curassavica L.) CG host plant species we found no relationship between CG and oviposition on the low CG species, but a negative relationship in the high CG species. This corroborates our findings on oviposition on single host species in the field.

4. We also record the first indication of a physiological cost of monarch larvae feeding on plants high in CG. There was a significant negative relationship between survival of first instar larvae and CG levels in plants. This study opens the way for further work on the association of monarch butterflies and their toxic milkweed hosts.
Variation in ovariole number and egg size of species of Dacus (Diptera; Tephritidae) and their relation to host specialization
Authors: FITT GARY P.
Published: March 2008

Abstract. 1. An analysis of the number of ovarioles/ovary is presented for fourteen species of Dacus ranging from broad generalists (D.tryoni (Frogg.)) to strict host specialists (D.aglaia Hardy). For eight species data on egg size and the incubation time of eggs is also presented. Interrelationships among these life history variables and their relationships to host specialization were examined.

2. There was a broad positive relationship between the breadth of the natural host range (i.e. excluding cultivated fruits) and ovariole number (and hence potential fecundity). Highly polyphagous species had thirty‐five to forty ovarioles/ovary while the specialists ranged from eight to twenty.

3. D.musae (Tryon), a specialist on banana, was an exception having an ovariole number similar to that of the most polyphagous species.

4. There was no clear relationship between egg size and ovariole number across eight species, though monophages were not fully represented in this analysis. Among these eight species there was no significant relationship between wing length and egg length, nor was there any such relationship among individuals within species.

5. There was considerable variation among species in the incubation time (at 25°C) for eggs, ranging from 24 h for D.cucumis French to 53 h for D.cacuminatus (Hering). This variation was only weakly related to egg size, though D.cucumis produced the largest eggs of any species examined.

6. Possible explanations for a relationship between potential fecundity and host range are discussed in terms of the balance between the abundance of host resources for generalists and their predictability for specialists. However, the observed relationship between ovariole number and host range must remain tentative, given that only fourteen species from one genus have been examined. Considerably more data is required for other dacines, for species in other tephritid subfamilies, and for other phytophagous insect groups to determine whether the relationship is generally applicable.
Influences of host feeding‐niche and foodplant type on generalist and specialist parasitoids
Authors: HAWKINS BRADFORD A. , ASKEW R. R. , SHAW MARK R.
Published: March 2008

Abstract. 1. We classified the parasitoids of 185 British herbivorous insect species as being koinobionts (which should tend to be specialists) or idiobionts (potential generalists) to examine the influences of host feeding‐niche and foodplant type on the numbers of parasitoid species attacking individual host species.

2. The majority of parasitoid species of exophytic hosts are koinobionts, whereas endophytic hosts support mainly idiobionts.

3. Parasitoid assemblage size increases with host foodplant size and complexity; for endophytic hosts this is due to an increase in idiobionts on hosts on large plants, but for exophytic hosts it is the number of koinobionts that increases with foodplant size.

4. Comparison of these patterns with those predicted under a competition hypothesis suggests that parasitoid communities associated with endophytic hosts may be commonly limited by interspecific competition, whereas those of exophytic hosts probably are not.
Strategies of mate finding in the European field cricket (Gryllus campestris) at different population densities: a field study
Authors: HISSMANN KAREN
Published: March 2008

Abstract. 1. Members of a field population of Gryllus campestris L. varied in their walking and calling activity. In both sexes, some individuals occupied burrows whereas others walked around in the observation area. Males at burrows could be either silent or calling.

2. In the course of one summer, population density decreased and the initial balanced sex ratio changed to a large surplus of males.

3. At high population density, there were equal numbers of non‐calling males at burrows, calling males at burrows and walking males, while walking females predominated over females at burrows. Non‐calling males at burrows achieved more encounters with females than did calling and walking males. Females met males by walking through the population and by waiting at burrows. Thus, calling and phonotaxis were not essential for mate finding and calling was less effective than previously thought.

4. At low population density calling males predominated. Calling males at burrows achieved the most encounters with females. Females met males only by walking around in the population area. Calling was thus more important in mate finding than at high population density.

5. Changes in sex ratio and population density may cause the flexibility in mate finding behaviour of individual crickets.
Interactions among leaf toughness, chemistry, and harvesting by attine ants
Authors: NICHOLS‐ORIANS COLIN M. , SCHULTZ JACK C.
Published: March 2008

Abstract. 1. Young and mature leaves of a tropical legume, Inga edulis var. minutula Schery, are strikingly different in secondary chemistry, especially condensed tannins, and leaf toughness.

2. Bioassays with the two different leaf types indicate that leaf cutter ants, Atta cephalotes (L.), always find mature leaves relatively more acceptable than young leaves when selection was based on chemical cues.

3. Since extracts of young leaves show greziter inhibition of fungal pectinases we suggest that leaf‐cutter ants are capable of distinguishing which leaf types are most suitable for the growth of their symbiotic fungus.

4. However, mature leaves are 3 times tougher than young leaves and this prevents leaf‐cutter ants from harvesting the more suitable mature leaves.

5. Consequently, bioassays which require cutting before leaf removal indicate that some colonies actually harvest more from the less suitable young leaves.

6. We suggest that the quality of a colony's habitat may indicate whether a colony will harvest more of the less suitable young leaves. Colonies which are harvesting from highly suitable host plants avoid the tropical legume I.edulis while those in poorer habitats accept I.edulis but, because of leaf toughness, mostly harvest the less suitable young leaves.
The predators of insects
Authors: SCHOENLY KENNETH
Published: March 2008

Abstract. 1. Insect–insectivore trophic relations were reviewed using presence–absence data from sixty‐one invertebrate‐dominated food webs and fifteen food webs from Briand's (1983) original forty web collection. From counts of prey links in higher taxa (orders, classes, phyla), six phyla and thirteen classes of non‐insect insectivores and fourteen orders of insect predators and prey were found.

2. Detritus‐based habitats (phytotelmata, felled logs, carcasses, dungpads) harboured fewer orders of insects, that interact with other insects, than webs from grazer‐based (host plants, some galls) and mixed‐based systems (aquatic webs). Consumer–resource networks of higher insect taxa in these webs shared several features found in some species‐level biological networks: the trend was towards few pairs of strong asymmetrical links, several weak links and many null interactions.

3. From counts of insect predator–insect prey links, hymenopterans as terrestrial predators and parasitoids interacted with the most number of higher insect taxa. Hymenopterans were also linked as prey more often than other terrestrial insects. In freshwater habitats, plecopterans were linked as predators more often than other aquatic taxa, whereas dipterans were listed as prey more often than other insects.

4. Dipterans were linked in the diets of non‐insect insectivores from seven of eight common taxonomic classes. Arachnids were identified as insect predators by food web researchers in the largest number of webs, followed by passerine birds and cyprinodont fishes. From analysis of prey links at the ordinal level, predaceous insects were less polyphagous than other predators (other ectotherms and endotherms).

5. Analysis of chain lengths, as expected, showed that insect prey occupied mostly lowermost trophic levels, non‐insect insectivores were found mostly at uppermost trophic levels, and predaceous insects were found mostly at intermediate trophic levels across most habitats.

6. This analysis offers evidence that insects are not just occupying intermediate trophic levels in some communities. Indeed, some taxa feed at the upper ends of long food chains, for example eupelmids in galls, staphylinids in carcasses, and perlid plecopterans in streams.
Pre‐oviposition mate‐guarding and mating behaviour of Argia vivida (Odonata: Coenagrionidae)
Authors: CONRAD K. F. , PRITCHARD G.
Published: March 2008

Abstract. 1. At Halcyon Hotsprings, British Columbia, Canada, male and female Argia vivida Hagen encountered to mate in two different ways.

2. In the morning (before 12.30 hours solar time), males basked at sunspots in the forest and darted out at passing females, attempting to take them in tandem (the first method of encounter).

3. If a male was successful, the pair engaged in a 31.3±4.8 min copulation followed by an hour of tandem flight before beginning oviposition.

4. As the day progressed, unmated males moved slowly toward the water and arrived at the water at about the same time as the earliest ovipositing pairs (1131±27.5 min solar time).

5. Males retained their grasp on their mates during oviposition (contact‐guarding) but since some tandems separated during oviposition, non‐tandem males at the water could capture recently released, gravid females (the second method of encounter).

6. The new pairs performed a brief copulation (10.2±3.38 min) and began ovipositing immediately thereafter.

7. Some females that avoided recapture attempted to oviposit unguarded.

8. We believe the long duration of morning copulations and period of tandem constitute a male strategy, which we call ‘pre‐oviposition guarding’, to guard females until it is warm enough at the oviposition site for the females to begin ovipositing.

9. Separation of tandems during oviposition may be initiated by either member of the pair and we suggest that one benefit to a female of leaving a guarding mate is increased efficiency of oviposition when the intensity of male harassment is low.

10. The mating system of A. vivida thus comprises a series of complementary male and female mating behaviours.
The influence of host size on sex ratios in the parasitoid Diglyphus begini (Hymenoptera: Eulophidae)
Authors: HEINZ KEVIN M. , PARRELLA MICHAEL P.
Published: March 2008

Abstract. 1. Sex ratio in the ectoparasitoid, Diglyphus begini (Ashmead), attacking larvae of the dipterous leafminer Liriomyza trifolii (Burgess) in glasshouse marigolds, is best depicted by a model where sex ratio varies as a function of host size.

2. Male D. begini progeny are produced in hosts significantly smaller in size than those producing female progeny.

3. Female wasps attack and oviposit on the largest leafminer larvae available and whether a host is large or small depends upon the size of the other hosts attacked.

4. Diglyphus begini females adjust the thre:shold size for the change‐over in sex allocation relative to the size of hosts attacked; however, the sex ratio is maintained at between 60% and 70% males.

5. The patterns observed in these glasshouse studies are not due to sex‐specific differential mortality or superparasitism.
Differential susceptibility to variable plant phenology and its role in competition between two insect herbivores on oak
Authors: HUNTER MARK D.
Published: March 2008

Abstract. 1. The population dynamics of Tortix viridana L. (Lepidoptera: Tortricidae) and Operophtera brumata L. (Lepidoptera: Geometridae) on the pedunculate oak Quercus robur L. are driven by the degree to which larval hatch coincides with oak budburst in spring.

2. Experiments with first instar larvae demonstrate that T. viridana has a much narrower dietary breadth, is less inclined to disperse from closed oak buds, and can resist starvation for longer periods than the polyphagous O.brumata.

3. As a result of its specialist foraging strategy, T. viridana may be less susceptible to mortality associated with colonization of oak in spring than O.brumata. This may explain why T. viridana populations are, on average, higher.

4. These results are discussed in the light of previous work which described the competitive advantage of O. brumata in field cage experiments. Stochastic mortality factors, which drive population change in both species independently of competition, favour T.viridana larvae, and over‐ride the competitive superiority of O.brumata.
Insect responses to plant water deficits. I. Effect of water deficits in soybean plants on the feeding preference of Mexican bean beetle larvae
Authors: McQUATE GRANT T. , CONNOR EDWARD F.
Published: March 2008

Abstract. 1. We examined the preference of larvae of the Mexican bean beetle, Epilachna varivestis Mulsant (Coleoptera: Coccinellidae), for foliage of soybean (Glycine max [L.] Merr.) grown under several levels of water deficit. Third instar larvae were exposed simultaneously to excised foliage from plants that were either well‐watered (control) or had experienced water deficits (treatment).

2. Water‐deficient plants were re‐watered 12 h prior to initiating feeding trials to eliminate physical differences between control and treatment foliage such as leaf water potential, diffusive resistance, relative water content, and foliage toughness.

3. Examination of the free amino acid contents of re‐watered and excised foliage indicated that amino acid concentrations increased markedly in foliage grown under water deficits, and that this increase persisted during the preference tests.

4. Larvae preferred control foliage, but shifted preference to treatment foliage under mild water deficits. When the leaf water potential of water‐deficient treatment foliage was lower than – 1.13 MPa or when it was more than 0.5 MPa lower than that of control foliage, larvae preferred to feed on foliage from well‐watered control plants.

5. The expression of preference for well‐watered control foliage was coincident with increases in the concentrations of total free amino acids and individual free amino acids in the water‐deficient treatment foliage.

6. These results are inconsistent with White's (1974) hypothesis because Mexican bean beetle larvae avoid plants grown under water deficits that have increased concentrations of free amino acids.
Phenology of nutritional differences between new and mature leaves and its effect on caterpillar growth
Authors: STAMP NANCY E. , BOWERS M. DEANE
Published: March 2008

Abstract. 1. We determined the phenology of the shrub Spiraea latifolia Ait. Bork. (Rosaceae), which has indeterminate shoot growth, and the effects of phenological changes in leaf quality on growth rate of the early‐spring feeding buckmoth caterpillars, Hemileuca lucina Hy. Edw. (Saturniidae).

2. Leaves, regardless of whether they were newly expanded or several weeks old, were tougher later in the growth season (mid‐June) than similarly aged leaves collected earlier; correspondingly, water and nitrogen content for leaves of all ages declined through the larval period. By July, newly expanded leaves had no more nitrogen than mature leaves.

3. Relative growth rate of third instar larvae fed new leaves or a mixture of new and mature leaves in early June was higher than that of those fed mature leaves, and efficiency of conversion of digested food to biomass was higher for larvae fed new leaves than for those fed mature leaves or a mixture.

4. In another experiment, larvae were reared on new leaves through the fourth instar and then fed a diet of new, mature or a combination of new and mature leaves, a regimen that was similar to the phenologies of both plants and caterpillars in the field. There was no difference in time to pupation or pupal weights among these treatments.
The effect of host‐plant quality on the survival of larvae and oviposition by adults of an ant‐tended lycaenid butterfly, Jalmenus evagoras
Authors: BAYLIS M. , PIERCE N. E.
Published: March 2008

Abstract.

Juveniles of the Australian lycaenid butterfly, Jalmenus evagorus (Donovan), secrete to ants a solution of sugars and amino acids, primarily serine. The attendant ants protect the larvae and pupae from parasites and predators.

The effect of caterpillar nutrition on the defence provided by ants was investigated. Potted food plants of Acacia decurrens were either given water containing nitrogenous fertilizer or were given water alone. Fertilized plants had a higher nitrogen content than unfertilized plants.

Fifth instar larvae of J.evagoras feeding on fertilized plants attracted a larger ant guard than those feeding on unfertilized plants. In the absence of caterpillars, ants were not differentially attracted to fertilized and unfertilized plants.

In the presence of ants, over a 10‐day period, larvae on fertilized plants survived better than larvae on unfertilized plants. In the absence of ants larvae survived equally on fertilized and unfertilized plants. It is concluded that larvae on fertilized plants attracted a larger ant guard, and thereby survived better, than larvae on unfertilized plants.

Adult females of J. evagoras preferred to lay egg batches on fertiized, rather than unfertilized plants, but they did not lay larger egg batches.
Oviposition response of Simulium reptans (Diptera: Simuliidae) to the presence of conspecific eggs
Authors: COUPLAND JAMES B.
Published: March 2008

Abstract.

The oviposition behaviour of Simulium reptans L. is described from two sites on the River Spey, Scotland. Female aggregations were observed immediately downstream of oviposition sites and were composed mainly of gravid flies (range 60–80%0) together with smaller numbers that were either freshly bloodfed (range 2–17%) or infected with mermithid nematodes (range 0–30%).

The time from landing on the oviposition sites to the onset of oviposition was recorded. The time in the presence of greater than 1‐day‐old eggs did not significantly differ from sites with no eggs present. However, the presence of freshly laid or I‐day‐old eggs significantly shortened the time to onset of oviposition. The cues that elicit oviposition are unknown but it is speculated that they may involve a pheromone.
Host population structure affects field sex ratios of the heteronomous hyperparasitoid, Coccophagus atratus
Authors: DONALDSON J. S. , WALTER G. H.
Published: March 2008

Abstract.

Second instar Filippia gemina de Lotto scale insects are the preferred hosts of female Coccophugus atrutus Compere larvae. These scale insects were found on their host plants, Chrysanthemoides monilifera Norlindh and Cliffortia strobilifera Mettenius, only at certain times during a 1 year sampling programme.

Late larval instars and prepupae of C.atratus, and a Metaphycus species, are the preferred hosts of male C.atratus larvae. These hosts, although they occurred on the same host plants as hosts for female C.atratus, were most numerous at different times during the sampling period.

The ratio of hosts suitable for C.atratus varied from a predominance of hosts suitable for females through to a predominance of hosts suitable for males. Sex ratios of adult C.atratus followed a similar trend but did not reflect, exactly, the ratio of available hosts. Differences in mortality between sexes and hyperparasitism may account for this anomaly.

Variable population sex ratios observed in C.atratus apparently result from the behaviour of individual females in which brood sex ratios are dependent on the relative availability of hosts for males and hosts for females. This behaviour, in turn, may result from variability in the host population structure but may also result from selection pressures operating at the time that heteronomous hyperparasitism evolved.
Sperm competition in Callosobruchus maculatus (Coleoptera: Bruchidae): a comparison of two methods used to estimate paternity
Authors: EADY P. E.
Published: March 2008

Abstract.

This study investigates sperm competition in Cullosobruchus maculatus (F.) (Coleoptera: Bruchidae), and is the first study to make a direct, controlled comparison of the sterile male and genetic marker techniques to estimate sperm precedence.

P2 values (the proportion of offspring fathered by the second male) obtained from the two methods were similar: P2 (sterile male) = 0.82, P2 (genetic marker) = 0.85. Both methods are therefore suitable for studying sperm precedence if the appropriate correction factors are applied.

The importance of general fertilization ability, differential fertilizing capacity and differential zygote mortality are examined and discussed.
Host‐plant mediated geographic variation in the life history of Platycotis vittata (Homoptera: Membracidae)
Authors: KEESE MARK C. , WOOD THOMAS K.
Published: March 2008

Abstract.

The oak treehopper Platycotis vittata (Fabricius) is bivoltine throughout its range with discrete generations in the early spring and autumn. Females of both generations diapause.

Latitudinal variation in the timing of life history exists among four populations of P. vittata along the eastern coastal plain of the United States.

We disrupted synchronization between P.vittata life history and host‐plant phenology in the springs of 1984 and 1985 by placing southern populations on northern trees with a different phenology. This caused some females to oviposit abnormally in late spring, without entering diapause. The offspring of these females had reduced reproductive success.

Winter diapause can be broken by providing females with a newly flushing tree with high levels of amino nitrogen in the sap. Females terminated winter diapause on trees breaking winter dormancy while females on trees still in winter dormancy did not, under identical photoperiod and temperature regimes.

The role of host‐plant mediated life history variation as a process promoting intraspecific geographic differentiation in the arboreal sap‐feeding guild is discussed.
Mortality risk versus food quality trade‐offs in ants: patch use over time
Authors: NONACS PETER , DILL LAWRENCE M.
Published: March 2008

Abstract.

Foragers of the ant species Lasius pallitarsis (Provancher) and Myrmica incompleta Provancher were given access to two food patches that differed in nutritive quality. In about half of the trials, the higher quality patch also had a mortality risk for the foragers in the form of a large Formica subnuda Emery ant located along the trail. Colonies were given access to the food for 4 or 24 h, every second day.

Use of the higher quality patch by L.pallitarsis foragers was depressed by the mortality risk. In contrast to the predictions of a food stress hypothesis, foragers used the risky patch more in the longer access trials. This appears due to a decline in the activity level of the F.subnuda, which results in a significantly lower mortality risk per trip.

M.incompfeta also significantly decreased their use of the higher quality patch when a F.subnuda was present. However, the length of time a colony had access to the patches had no effect on the use of the risky patch. M.incompleta foraging behaviour seems relatively insensitive to short‐term food stress or changing levels of mortality risk.

The differences between species in their exploitation of patches and reactions to F.subnuda are discussed in terms of the species’natural history.
Habitat characteristics of grassland Pterostichus species (Coleoptera, Carabidae)
Authors: RUSHTON S. P. , LUFF M. L. , EYRE M. D.
Published: March 2008

Abstract.

Pterostichus species were sampled on ninety‐two sites distributed throughout north‐east England using pitfall trapping.

The incidence of each species was related to measured site environmental variables using logistic regression.

Four species groups were identified on the basis of size. The extent of overlap in habitat types between species in each group varied. Two large species overlapped considerably whilst the smaller species showed different responses to one or more environmental variable.

Possible causes of the differences in habitat overlap between Pterostichus species are discussed.
Two forms of egg defence in a chrysomelid beetle: egg clumping and excrement cover
Authors: DAMMAN HANS , CAPPUCCINO NAOMI
Published: March 2008

Abstract.

Field experiments demonstrated that the faecal covering that female Microrhopala vittata (Fabr.) (Coleoptera: Chrysomelidae) place over their egg masses significantly reduces egg mortality.

The bottom egg in the egg mass, which lies against the leaf of the host plant, suffers significantly higher mortality than the other eggs in the egg mass.

The parasite Chrysonotomyia sp. (Hymenoptera: Eulophidae) generally parasitizes only the bottom egg in the egg mass, while predators rarely penetrate the faecal covering.

No significant relationship was found between mortality and the number of egg masses per leaf.

By placing eggs in masses, females may ensure that at least the upper eggs in any egg mass are effectively protected against virtually all natural enemies likely to pose a threat.
Contrasting age structures in cave cricket populations: patterns and significance
Authors: CARCHINI GIANMARIA , RUSSO CLAUDIO DI , SBORDONI VALERIO
Published: March 2008

Abstract.

Adaptation to life in caves, as a seasonally constant environment, is expected to affect several life history traits. In this paper we investigate the age structure and phenology of twenty‐seven Dolichopodu cave cricket populations from artificial and natural caves subjected to different environmental regimes and to different availability of food resources.

Morphometric data clearly revealed the occurrence of different age structures and phenology, basically indicating two contrasting patterns.

In artificial caves, which have been colonized by Dolichopoda only in historical times and where food resources and climate are chiefly dependent upon surface environment, age structure was seasonal. In contrast, in most natural caves, where cricket colonization appears to be much older and stability of both climatic parameters and trophic resources is higher, age structure was diverse and aseasonal.

However, a seasonal age structure also occurs in natural caves characterized by either recent origin or by a low temperature regime. This suggests that age structure in Dolichopoda is influenced by historical factors, stability of food resources and also by environmental stress.