bluuebunny/crossref_metadata_2025 huggingface dataset:
Egg‐laying by the speckled wood butterfly (Pararge aegeria): the role of female behaviour, host plant abundance and temperature
Authors: SHREEVE T. G.
Published: March 2008

ABSTRACT.

Egg‐laying by Pararge aegeria (L.) was studied in relation to host plant abundance, temperature and behaviour in one woodland site in central England.

Eggs were laid on the undersides of leaves of fifteen of thirty‐one species of grass located in the study site. Most were deposited singly although on several occasions a number of females laid on a single leaf.

There was no clear relationship between host plant abundance and host plant use, the species used being widespread and abundant.

Most eggs were laid on plants within the temperature range 24–30°C. In spring and later summer these sites were in sunlit open areas but in midsummer they were in the woodland ground layer.

Females distributed their eggs over a large area, usually making a dispersal flight after laying an egg.
The effects of foliage damage on casebearing moth larvae, Coleophora serratella, feeding on birch
Authors: BERGELSON JOY , FOWLER SIMON , HARTLEY SUSAN
Published: March 2008

ABSTRACT.

Mechanical damage to birch (Betula pendula Roth) leaves leads to an increase in the concentration of phenolic compounds, which spreads throughout the leaf within 8 days.

Coleophora serratella L. (Lepidoptera: Coleophoridae) apparently responds to this chemical change over a similar time scale. Within 24 h of pin‐pricking leaves the casebearer moves from the immediate vicinity of the damage, but is just as likely to move to an undamaged portion of the damaged leaf as to vacate the leaf entirely. After 8 days mines on undamaged portions of damaged leaves were significantly smaller than mines on undamaged leaves.

Furthermore, Coleophora serratella reared on damaged trees took an average of 3 days longer to develop than those reared on undamaged trees.

It has been suggested that increased movement in response to damage‐induced chemical changes causes hyperdispersed damage on plant foliage. Both within and between‐leaf casebearer damage patterns were shown to be aggregated on birch.

Thus although mechanical damage can induce chemical and behavioural changes in the field, these are not reflected in the observed damaged patterns. We speculate on several possible reasons for this.
The osmaterial glands of the swallowtail butterfly Eurytides marcellus as a defence against natural enemies
Authors: DAMMAN HANS
Published: March 2008

ABSTRACT.

Natural enemies account for almost all mortality of zebra swallowtail caterpillars (Eurytides marcellus [Cramer]) feeding on pawpaw (Asimina spp.) in Florida.

The osmaterial glands of the third instar caterpillars reduce predation rates in the spring, but not later in the season.

The seasonal decline in effectiveness of osmateria in deterring natural enemies probably stems from a reduction in the importance of the predators that are repelled by osmateria.
Attachment may be a basis for specialization in oak aphids
Authors: KENNEDY C. E. J.
Published: March 2008

ABSTRACT.

The potential role of tarsal attachment in host selection was studied in the specialist aphids Tuberculoides annulatus Hartig and Myzocallis schreiberi Hille Ris Lambers and Stroyan.

M.schreiberi could walk freely on its host, Quercus ilex and on Q.robur, whereas T.annulatus could walk freely on its host, Q.robur but had difficulty on Q. ilex.

Attachment to the rough‐textured leaves of Q.robur was achieved by means of the pretarsal claws, and to the smooth upper surface of individual trichomes on the lower surface of Q.ilex using flexible pretarsal empodia.

Both behavioural and allometric differences can account for the inability of T.annulatus to grip onto Q.ilex.

The role of attachment by phytophagous insects in host plant resistance and selection is discussed.
A comparative study of winter survival in two temperate Collembola
Authors: Van Der WOUDE H. A. , VERHOEF H. A.
Published: March 2008

ABSTRACT.

We studied winter survival of two temperate collembolan species, Orchesella cincta (L.) and Tomocerus minor (Lubbock), that overwinter in adult and juvenile life stages.

A significant seasonal variation in cold hardiness, measured as lethal temperature after 24 h exposure, was found for both species. There was no difference between juveniles and adults in cold hardiness. O.cincta was more cold tolerant than T.minor.

A group of high and a group of low values for lethal temperatures could be distinguished.

Frost periods induced gut evacuation in O.cincta, but not in T.minor.

During frost periods no extra winter mortality was found in T.minor. This species moved down the soil profile as a response to a frost period without snow cover.

The winter mortality of O.cincta was difficult to estimate, since part of the population remained above ground in trees and escaped from sampling. The smallest size classes, which are restricted to the litter, had a lower winter mortality than T.minor.
Primary sex‐ratio and differential progeny survivorship in solitary haplo‐diploid parasitoids
Authors: WELLINGS P. W. , MORTON R. , HART P. J.
Published: March 2008

ABSTRACT.

A method of partitioning emergence sex‐ratio to give estimates of primary sex‐ratio and male and female offspring survival from oviposition to emergence in solitary haplo‐diploid parasitoids is presented.

This method is applied to sex‐ratio data from a larval parasitoid, Aphidius ervi Haliday, and a pupal parasitoid, Coccygomimus turionella L., parasitizing a range of host types.

There was no evidence of facultative control of primary sex‐ratio in either species. Parasitoid emergence sex‐ratios were similar for all host sizes attacked by C. turionella. In contrast, emergence sex‐ratios of A.ervi showed a significant male bias in smaller hosts. This shift in emergence sex‐ratio was attributable to differential progeny survival.

Pre‐emergence mortality in both species was a function of host size, with few offspring surviving from small hosts. This suggests that host size may be an important component in the dynamics of host‐parasitoid interactions.

The evolution of sex‐ratio regulatory mechanisms in solitary haplo‐diploid parasitoids is discussed in the context of parasitoid life‐history. We suggest that there is a constraint to the evolution of the facultative control of primary sex‐ratio in parasitoids attacking larval stages as a result of the uncertainty of future host resource acquisition rates.
Does alary dimorphism imply dispersal dimorphism in the waterstrider,Gerris remigis?
Authors: FAIRBAIRN D. J.
Published: March 2008

ABSTRACT.

The hypothesis that wing dimorphism reflects dimorphism for dispersal ability is tested in two populations of stream‐dwelling waterstriders,Gerris remigisSay, in southern Quebec, Canada.

Movements were assessed directly by recaptures of marked adults, and indirectly by comparisons of residence times and patterns of disappearance of macropterous and apterous morphs. Sampling was done weekly, over a period of 26 months, and 4828 adultG.remigiswere individually marked during this time.

Movements of >100 m were very rare for both morphs. The movement patterns of the two morphs were very similar, and differed only over the winter, when no macropters moved upstream. This latter observation suggests that macropters may be less successful than apterous individuals at moving overland, or rowing against a current at this time of year.

Residence times and patterns of disappearance of the two morphs were very similar during all seasons.

These results suggest that macropterousG.remigisdo not, in general, disperse using any means unavailable to the apterous morph, and that macropters in this species should not be simply categorized as long‐distance dispersers.
Temporal constancy in grasshopper assemblies (Orthoptera: Acrididae)
Authors: JOERN ANTHONY , PRUESS† KENNETH P.
Published: March 2008

ABSTRACT.

Temporal constancy in the structure of grasshopper assemblies (about forty‐five species each) from two types of North American grasslands was assessed; one site was followed 25 years and the other 7 years.

Densities and relative abundances varied but composition of assemblies based on ranks suggested significant structure when three or more species were included in the analysis.

Results compared favourably with other insect herbivore assemblies which have been examined; variability in population change was intermediate along the spectrum of organisms which have been studied.
The harmonic radar: a new method of tracing insects in the field
Authors: MASCANZONI DANIEL , WALLIN HENRIK
Published: March 2008

ABSTRACT.

A novel technique for tracing the movements of insects in the field is described.

The detection system is based on radar technology originally developed for locating avalanche victims. The key of the system is a tiny electronic diode that, glued to the insect, can reflect microwave beams emitted by portable detection equipment.

The technique has been successfully tested in a field‐tracing experiment with carabid beetles. The results show that these insects are capable of dispersing surprisingly long distances in a relatively short period of time.
Effects of root nodules and taproots on survival and abundance of Sitona hispidulus (Coleoptera: Curculionidae) on Medicago sativa
Authors: QUINN MARK A. , HOWER ARTHUR A.
Published: March 2008

ABSTRACT.

The effects of food resources on populations of larvae of Sitona hispidulus (F.), a root and nodule herbivore of Medicago sativa L., were investigated in 1983 and 1984.

Density‐dependent mortality among first‐instar larvae indicated that a lack of available root nodules, the primary resource for first instars, contributed to the 66.2±5.2% and 80.7±4.1% mortalities of first‐instar larvae in 1983 and 1984, respectively. Initial densities of larvae entering the soil were 31.7±2.4 and 15.6±1.3 per soil sample (10.5 cm diam. ×15 cm deep) in 1983 and 1984, respectively (±SEM).

Survivorship and number of first‐instar larvae per soil core sample were significantly related to number and biomass of nodules per soil sample. Percentage soil moisture was not consistently correlated with survivorship and number of larvae per soil sample.

Numbers of second‐ and third‐instar larvae were not consistently correlated with either nodule or taproot biomass.

Numbers of fourth‐instar larvae were associated with taproot biomass, suggesting that taproot surface area may also limit population levels of S.hispidulus. No correlations were found between taproot and nodule biomass on any sampling date indicating that high numbers of fourth‐instar larvae associated with larger taproots were not merely due to a greater survival of first instars associated with larger taproots.

The study suggests that population levels of nodule‐herbivores are controlled by the availability of root nodules. A sparse distribution of nodules results in high levels of mortality among nodule‐herbivores of Medicago sativa.
Aggregation of parasitoids and density‐independence of parasitism in field populations of the wasp Aphytis melinus and its host, the red scale Aonidiella aurantii
Authors: SMITH A. D. M. , MAELZER D. A.
Published: March 2008

ABSTRACT.

Repeated counts were made of the number of adult Aphytis melinus (DeBach) wasps per fruit on Valencia oranges in an orchard over two successive periods. Resulting rates of parasitism per fruit were measured at the end of each period.

For both periods, corresponding to high and low mean numbers of adult parasites, there was a significant positive regresssion of adult wasps per fruit on the number of available hosts per fruit. However, there was a high level of variability about the regression, and the overall aggregative response appears to be weak.

For both periods, rates of parasitism per fruit were independent of host density per fruit and they showed a high level of variability at all densities. Similar patterns were found in another, commercial, orchard over a wide range of mean host densities.

There was no evidence for aggregation of parasites or density dependence of parasitism at a patch size corresponding to the whole tree.

Suggestions based on some host‐parasitoid models, that aggregations of parasite attack in areas of high host density are necessary for effective biological control, are rejected. However, the model of Hassell (1982), incorporating aggregation of parasites and limitations on the effectiveness of the parasite, seems to fit the data quite well.
Wing and flight muscle polymorphism in a lygaeid bug, Horvathiolus gibbicollis: determinants and life history consequences
Authors: SOLBRECK CHRISTER
Published: March 2008

ABSTRACT.

Horvathiolus gibbicollis (Costa), a ground‐living seed‐feeding bug of the mediterranean region, has two wing morphs. In macrop‐terous bugs both pairs of wings are fully developed. In brachypterous ones forewings are reduced to about two‐thirds and hindwings to less than a third of their length in macropters.

Each morph bred true with regard to wing length when reared under variable density, food and temperature conditions for several generations.

All F1 offspring between crosses of the two morphs were brachypterous. In F2 approximately 25% were macropters and 75% brachypters implying monogenic control of wingform.

Flight muscles in macropters vary from fully developed to totally reduced. This variation is determined by environmental conditions during adult life. Most young adult bugs have flight muscles, and totally starved or unmated bugs retain their flight muscles. Fed and mated females histolyse flight muscles as they start laying eggs, while most males of the same group retain their muscles.

Brachypterous bugs have a smaller thorax and larger abdomen than macropterous ones.

Brachypterous bugs reach adulthood slightly before macropterous ones, and they have a distinctly shorter adult preoviposition period.

Lifetime egg production does not differ significantly between the two wing morphs. However, the temporal pattern of egg laying is different in the two morphs. The mx‐curve of macropters starts later, then attains a higher peak and finally decreases faster than that of brachypters.

Initially, macropters lay smaller eggs than brachypters, but egg volume increases with age in macropters and eventually approaches that of brachypters.

The initial increase in reproductive effort (egg volumexegg number) of macropters is concomitant with wing muscle histolysis and the mobilization of thorax space for reproduction.

Adult survival rate does not differ between the morphs.
Habitat choice of some field‐inhabiting carabid beetles (Coleoptera: Carabidae) studied by recapture of marked individuals
Authors: WALLIN HENRIK
Published: March 2008

ABSTRACT.

Habitat choice of some field‐inhabiting carabid beetles was studied in the field, and included the adult‐overwintering Bembidion lampros Herbst, Pterostichus cupreus L. and Agonum dorsale Pontoppidan, and the larval‐overwintering Trechus secalis Paykull, Pterostichus melanarius Illiger, P.niger Schaller and Harpalus rufipes De Geer. These were compared to the forest‐inhabiting and adult‐overwintering species, Carabus nemoralis Müller.

Marked beetles were released in the centre of a circular enclosure which was placed on the edge between a cereal field and a wood. The direction of movement in this circle was compared with that in a control circle placed entirely in the cereal field.

In the field/wood circle, adult‐overwinterers and the larval‐overwin‐terer H.rufipes choose to move into the cereal field. The majority of T.secalis. P.melanarius and C.nemoralis, however, moved into the wood, while P.niger exhibited no preference.

In the field circle, adult‐overwinterers moved towards the more sun‐exposed parts of the circle, whereas the movements of larval‐overwin‐terers were random.

Some species‐specific characteristics considered important for habitat choice by these carabid beetles, and the relevance of these characteristics for their dispersal behaviour are discussed.
Larval densities and a life‐table for the gypsy moth, Lymantria dispar, estimated using the head‐capsule collection method
Authors: HIGASHIURA YASUTOMO
Published: March 2008

ABSTRACT. 1. In order to estimate the absolute larval density in each stage of a larval population of the gypsy moth, Lymantria dispar L., in a deciduous forest in northern Japan, the head‐capsule collection method was used. An estimate by this method was compared with estimates based on two kinds of frass collection methods.

2. Twenty‐one traps made of cloth were put in a study plot. Each trap was of 24.5 cm diameter. Larval head‐capsules falling into the traps were collected and sorted by hand. On the first sampling occasion, the population was also estimated using the frass‐collection method.

3. Larval numbers estimated by the head‐capsule collection method were almost identical to estimates by the two frass methods. Larval numbers entering the four larval instar were successfully estimated by the head‐capsule collection method, and an age‐specific life table was established using the resultant estimates.
Overwintering survivorship of pupae of the mimosa web worm, Homadaula anisocentra (Lepidoptera: Plutellidae), in an urban landscape
Authors: MILLER FREDRIC D. , HART E. R.
Published: March 2008

ABSTRACT. 1. Overwintering survivorship of pupae of the mimosa webworm, Homadaula anisocentra Meyrick (Lepidoptera: Plutellidae), was examined in several urban habitats in central Iowa during the winters of 1981–82, 1982–83 and 1983–84.

2. Survivorship and supercooling point temperatures were determined throughout the winters. Corroborative laboratory studies were conducted during the winter of 1982–83.

3. Minimum ambient temperatures that equalled or were below the supercooling point of the insect, at any time, were lethal.

4. Prolonged cold exposure below 0°C and above the supercooling point resulted in high mortality levels. To quantify this relationship, a concept of minimum‐temperature exposure was developed by tabulating the number of degrees that the daily minimum temperature was below 0°C for a given sampling period.

5. Some mimosa webworm pupae were found to overwinter in highly protected sites (2.5–5.0°C warmer than the ambient air temperatures) in the urban environment, resulting in less minimum‐temperature exposure and reducing the probability of reaching the lethal supercooling point temperature.
Guild structure of arthropods from Bornean rain forest trees
Authors: STORK N. E.
Published: March 2008

ABSTRACT. 1. 23275 arthropods collected by insecticide fogging from ten Bornean lowland rain forest trees were sorted to approximately 3000 species and assigned to guilds using two sets of criteria.

2. The rank order for proportions of guilds of species but not individuals is similar in tropical and temperate canopy samples.

3. Misplacement in the guild assignments of a few species can cause important differences in the proportions of certain guilds. This can seriously affect the results of comparisons of different samples, and views on proportional constancy of guilds of species on different trees.

4. Guilds of arthropod species such as chewers, suckers, all phytophages, predators, ants and tourists, occur in constant proportions in samples from different tropical trees and this constancy of proportion is similar in samples from groups of‘closely related’and‘distantly related’trees.

5. The guild concept of community structure and problems in assigning species to guilds are considered with respect to arthropod samples. The conclusions on constancy of proportion for guilds of species are tempered by remarks on the problems of guild composition.
Ecological correlates and heritability of reproductive variation in two co‐occurring grasshopper species
Authors: ATKINSON DAVID , BEGON MICHAEL
Published: March 2008

ABSTRACT. 1. Relationships are examined between mean egg size and possible selection pressures acting on two grasshopper species, Chorthippus brunneus (Thunb.) and Myrmeleotettix maculatus (Thunb.), co‐occurring at three sites in a sand dunes area.

2. Heavy eggs were laid where the mean crowding of hatchlings was high in relation to the amount of grasses with thin‐edged leaves. To a lesser extent, large eggs were also found in more desiccating conditions. Mean egg dry weights did not correlate with measures of crowding or measures of crowding in relation to total grass abundance.

3. Significant differences in egg size and clutch sizes were observed between the stocks of second generation, laboratory‐reared M.maculatus from three study sites. The significant difference in egg size (site 2 stock > site 1 stock) ran counter to the difference observed in the field but the difference in clutch size (site 3< site 2) was consistent with that observed between field populations.

4. We argue that egg size is primarily determined by selection pressures on the size of hatchlings but that predictably poor feeding conditions for juveniles and adults at site 2 results in the production of smaller adults which, in M.maculatus, then lay smaller eggs. We further argue that M. maculatus from site 2 have been selected to lay larger eggs for their body size and body condition in order to compensate partially for this environmental constraint.
Geographical variability in, and temperature effects on, the phenology of Maniola jurtina and Pyronia tithonus (Lepidoptera, Satyrinae) in England and Wales
Authors: BRAKEFIELD PAUL M.
Published: March 2008

ABSTRACT. 1. Geographical variability in, and temperature effects on, the mean date of adult flight period and the SD about this date are analysed for two univoltine, grassland butterflies in England and Wales from 1976 to 1985. Data were collected on the Butterfly Monitoring Scheme for Maniola jurtina (L.) at twenty‐nine sites and Pyronia tithonus (L.) at twenty sites.

2. Substantial variability for mean date and SD occurs between years and between sites. Changes in mean date between years tend to occur consistently at different sites. The species show some parallel in variation between sites, especially for mean date.

3. June maximum temperature accounts for 95% and 75% of the variation in mean date between years in M. jurtina and P. tithonus, respectively (r=‐0.97 and ‐0.87). Similar relationships occur for temperatures cumulated over the period of post‐winter development from March to July or August.

4. Greater geographical variability in phenology, and a generally less synchronized flight period in M.jurtina may be associated with broader habitat preferences than in P. tithonus.

5. The mean date of adult flight period remains at roughly the same date at more northerly latitudes. In M.jurtina the flight period becomes more synchronized, begins later and ends earlier in the north. P. tithonus shows little or no indication of such a response to latitude. This is discussed with regard to changes in season length and factors limiting the species’range.
Long adult life, low reproduction and competition in two sub‐Antarctic carabid beetles
Authors: DAVIES L.
Published: March 2008

ABSTRACT. 1. On the biologically impoverished sub‐Antarctic Ile de la Possession, Iles Crozet, Amblystogenium pacificum Putzeys and A.minimum Luff (Carabidae), both opportunistic carnivores, coexist in fellfield habitat above 120 m altitude, where they hunt prey in inter‐stone spaces.

2. Beetles show marked claw wear showing that many individuals survive to breed in their third or later year of adult life, and in some years, particularly in A.minimum, populations consisted largely of very old beetles. This coupled with evidence from ripe egg numbers, of rarity of tenerals and of larvae, shows that adult recruitment rates were usually very low.

3. In fellfield the coexisting species pair have non‐overlapping size distributions with A.pacificum the larger. In moorland A.pacificum adults occur in isolation and are smaller and overlap the size ranges of both species in fellfield. These facts are interpreted as character displacement or release, reflecting present‐day interspecific competition, probably for food. Supporting evidence was obtained in terms of apparent size‐differential survival of beetles of different ages.
The causes of seasonal changes in numbers of the yellow dung fly, Scathophaga stercoraria (Diptera: Scathophagidae)
Authors: GIBBONS D. S.
Published: March 2008

ABSTRACT. 1. Counts of adult Scathophaga stercoraria (L.) on cow pats were made in Houghall, County Durham, in 1964 and 1965.

2. A spring peak of numbers was due to adults (overwintered mainly as pupae or larvae) maturing and going to dung to breed. Numbers then dropped, rising to one or more peaks in late June—early July. In 1964 there was then a summer drop in numbers until late September. In 1965 high numbers persisted in summer associated with cooler, wetter weather. Autumn peaks in both years persisted until severe frosts or snow.

3. Mature adults, developed from eggs laid during the spring peak, form the first generation when breeding in mid‐late June. No clear generations can be identified after this, due to eggs being laid daily (females have successive gonotrophic cycles). Changes in adult numbers breeding reflects survival of eggs and newly‐hatched larvae 5–6 weeks earlier, and lower survival rates of adults in mid‐summer compared with spring and autumn.

4. Adult Scathophaga numbers in vegetation rose as numbers on dung dropped. Females dissected to count ovariole tunica dilatations showed that most flies in vegetation were immature, with some parous flies hunting insects to develop the next batch of eggs.

5. Females on dung were dissected and found to range from immature to seven‐parous. Those gravid for the first time were grossly under‐represented, possibly due to wider dispersal.

6. It is suggested that seasonal changes in this r‐strategist cannot be explained simply in terms of generations nor by the occurrence of adult diapause.
Effects of reproductive timing and colony size on the survival, offspring colony size and drone production in the honey bee (Apis mellifera)
Authors: LEE PHILIP C. , WINSTON MARK L.
Published: March 2008

ABSTRACT. 1. The effects of colony size and time of reproduction on the survival and size of offspring colonies and on drone production were examined for honey bees, Apis mellifera L. Drone and worker production and survival of parental and offspring colonies were monitored following swarming. Also, the temporal patterns of drone emergence and availability of unmated queens were examined.

2. Colony size at swarming was positively correlated with the number of workers invested in offspring colonies and the number of queens produced. However, colony size at swarming was not correlated with the number of offspring colonies produced.

3. Swarm size was positively correlated with drone and worker production after swarms were hived. Worker production of hived swarms was positively correlated with colony survival. Offspring queens which inherited a parental nest survived longer than queens in either primary swarms or afterswarms, presumably due to the advantage of inheriting a nest.

4. Drone emergence peaked just prior to swarming, the time when unmated queens were available. High drone production by colonies initiated by swarms probably reflected an attempt to reproduce prior to winter. The probabilities of a second swarming cycle within the same year and of surviving the winter were low for colonies initiated from swarms.
Diel patterns of activity of Thymelicus lineola adults (Lepidoptera: Hesperiidae) in relation to weather *
Authors: PIVNICK KENNETH A. , McNEIL JEREMY N.
Published: March 2008

ABSTRACT. 1. Daily patterns of activity, thoracic temperature (Tth) and thermoregulatory behaviour in relation to environmental conditions were studied in the European skipper Thymelicus lineola (Ochsenheimer) adults.

2. Daily activity was limited mainly by Tth, which in turn was dependent on air temperature (Ta) and sunlight. However, when light intensity fell to < 100 W m−2, skippers also became inactive.

3. Tth was sometimes as much as 12°C above Ta, and this was most pronounced under cool conditions when basking activity predominated.

4. Black globe temperature (Tbg) which, in the absence of wind, is influenced by both Ta, and radiant heat load in a manner similar to a basking butterfly, was used to approximate the maximum Tth attained by T.lineola through basking.

5. Both males and females basked at Tbg >20°C, and if this temperature was not attained, skippers remained inactive. As Tbg increased, basking activity declined more rapidly in males than in females. Basking bouts were also shorter in males.

6. Males also flew, fed and courted females at Tbg >20°C, while females only fed and flew at Tbg >22°C. The percentage of both sexes feeding and flying, and courting in the case of males, were positively correlated with Tbg.

7. In warm weather, males divided their time equally between flying and feeding, while females spent the majority of their time feeding. Feeding bouts were shorter and flying bouts were longer in males than in females. Flight duration in males was positively correlated with Tbg.

8. Skippers avoided, and, consequently laid fewer eggs in, shady areas.

9. Sexual differences in activity patterns in relation to weather reflect differences in the reproductive requirements of the two sexes.
Ecological methods for adult populations of Oryctes rhinoceros (Coleoptera, Scarabaeidae)
Authors: ZELAZNY B. , ALFILER A. R.
Published: March 2008

ABSTRACT. 1. For comparing assessment methods, O.rhinoceros (L.) populations were monitored in five 30–50 ha plots in southern Luzon, Philippines. No consistent correlations were found between number of beetles caught in traps, amount of palm damage and number of breeding sites. Apparently, plots were too small to account for fast dispersal of beetles.

2. Coconut cap traps baited with ethylchrysanthemumate attracted O.rhinoceros adults searching for breeding sites. Several factors were identified influencing catches but trapping was found to be unsuitable for accurately assessing pest populations.

3. A new method which gives estimates on the monthly number of O.rhinoceros attacks on coconut palms, was tested in the Maldives. Palms are climbed about once a year and the sequence of fronds, the number and the position of beetle cuts are recorded.

4. Reduction with age of the length of three teeth on the fore tibia of O. rhinoceros adults was studied in the Philippines. The data was insufficient to obtain a clear correlation between age and length of teeth.

5. The observations indicated that in the Philippines after leaving their site of pupation, O.rhinoceros adults spend about 5 weeks feeding on coconut palms. This is followed by a period of about 7 weeks in breeding sites and, on occasion, additional visits to palms. With these estimates it was possible to relate palm damage records with numbers of feeding adults.
Size and fecundity in the Jamaican gall‐midge Asphondylia boerhaaviae
Authors: FREEMAN B. E. , GEOGHGEN ANDREA
Published: March 2008

ABSTRACT. 1. The gall‐midge Asphondylia boerhaaviae Möhn galls weeds belonging to the Nyctaginaceae in Jamaica and other parts of the Caribbean. The species breeds throughout the year with a generation length of < 1 month.

2. In adult females, plots of wing length on hind tibial length, of maximum potential fecundity (m.p.f.) on wing length, and of m.p.f. on ovariole number, suggested the presence of a small morph, which the use of discriminant function analysis and other investigations confirmed. There was also good evidence of two size morphs in adult males.

3. Both body size and ovariole number had significant effects on m.p.f. but these effects were different in the two morphs. While the food plants had significant influences on size and fecundity, these were relatively small. The m.p.f. of the small morph was 125.8±11.1 eggs, and of the large morph 318.7±8.3 (95% cl).

4. Laboratory experiments on the flight performance of newly‐emerged midges indicated that the small morph was not dispersive and that about 80% of the large morph was dispersive. No differences in size, wing length or fecundity could be found between the two behavioural types of the large morph.

5. The nature of the polymorphism is unusual, particularly since the dispersive individuals potentially have similar (or greater) fecundity than the non‐dispersive ones.

6. Estimates of achieved fecundity (eggs actually laid, rather than m.p.f.) were 67.8±9.6 (field, minimum) and 138.9±30.4 (laboratory), the latter estimate being based on large‐morph females.
Seasonal variation in the reproductive strategy of the parasitic wasp Eulophus larvarum (Hymenoptera: Chalcidoidea: Eulophidae)
Authors: GODFRAY H. C. J. , SHAW M. R.
Published: March 2008

ABSTRACT. 1. Eulophus larvarum (L.) (Hymenoptera: Eulophidae) is a gregarious parasitoid of lepidopterous larvae feeding on broad‐leaved trees. Normally there are two generations a year.

2. Sex ratio in the spring generation of larvae is female biased. The bias is probably due to local mate competition as progeny from one brood emerge from their pupae in close proximity to each other.

3. Sex ratio in the summer generation of larvae is near equality. Local mate competition is absent as individuals from the same brood become separated during the winter.

4. Variation in sex‐ratio in the spring generation is consistent with a binomial model. Variation in sex ratio in the summer generation is much greater than expected from a binomial model and there is a large proportion of single‐sex broods.

5. Two hypotheses are put forward to explain the summer generation pattern: virgin oviposition, and strong intersexual competition.

6. No differences in clutch size were found between the two generations.
Insect‐induced chemical changes in young lodgepole pine (Pinus contorta): the effect of previous defoliation on oviposition, growth and survival of the pine beauty moth, Panolis flammea
Authors: LEATHER S. R. , WATT A. D. , FORREST G. I.
Published: March 2008

ABSTRACT. 1. Significantly more eggs were laid by adult female pine beauty moths (Panolis flammea (D&S)) on previously undefoliated lodgepole pine (Pinus contorta Douglas) saplings than on those which had been partially defoliated the year before.

2. The larval weights, mean relative growth rates and survival rates of P.flammea were lower on defoliated trees than on undefoliated trees.

3. Marked and significant differences between the monoterpene profiles of the shoot cortical oleoresin of defoliated and undefoliated trees were linked to oviposition preferences in P.flammea.

4. Differences occurred between the levels of soluble tannins in previously defoliated and undefoliated trees.

5. The results are discussed in relation to earlier work on insect‐induced changes in plants, and the significance of inter‐provenance differences in lodgepole pine response is assessed.
Communication of leaf suitability by gregarious eastern tent caterpillars (Malacosoma americanum)
Authors: PETERSON STEVEN C.
Published: March 2008

ABSTRACT. 1. Previous work has shown that leaf age affects recruitment trail marking by eastern tent caterpillars (Malacosoma americanum Fabr.). Young leaves of host plants elicit trail marking to a greater degree than mature leaves.

2. Experiments were conducted to establish the relationship between the differential behavioural responses of larvae to young and mature leaves and the suitability of foliage for larval growth and survival. Foliage of black cherry (Prunus serotina Ehrh.), a typical rosaceous host plant, was used for this comparison.

3. Larvae preferred young leaves to mature leaves in choice tests, and marked more to young leaves than to mature leaves in no‐choice tests.

4. Mature leaves supported adequate growth through two larval instars of rearing, but thereafter were unsuitable for growth. Larvae fed mature leaves had lower pupal weight, poorer survival, and grew less efficiently than larvae fed young leaves.

5. The results support the hypothesis that the trail communication system of eastern tent caterpillars is an adaptation to efficiently locate leaves which are favourable for larval growth and survival.
Host‐habitat location by Apanteles glomeratus and effect of food‐plant exposure on host‐parasitism
Authors: SATO Y. , OHSAKI N.
Published: March 2008

ABSTRACT. 1. The study investigates differences in the oviposition pattern of a braconid parasitoid, Apanteles glomeratus L., in three Pieris species in Japan in relation to their use of different cruciferous foodplants.

2. A.glomerutus females located various habitats of different crucifers. On field crops and exposed wild crucifers P.rapae crucivora Boisduval and P.napi japonica Shirôzu, which are both physiologically suitable hosts, were attacked at a high rate, although P.n.japonica is rare in such situations, while P.melete Ménétriès, which is a physiologically unsuitable host, was attacked slightly less frequently.

3. When P.n.japonica occurred on crucifers hidden by overshadowing vegetation, as it generally did, it suffered a very low level of parasitism by A.glomeratus, but if the overshadowing vegetation was cleared then a high rate of parasitism ensued.

4. The foodplant concerned, Arubis, was attractive to the parasitoid and not deleterious to its development in P.n. japonica, but it was not used by P.r.crucivora, which usually failed to develop on it under experimental conditions.

5. The parasitoid females could not locate foodplants hidden by overshadowing vegetation. Therefore the most important difference between foodplants in host‐habitat location was the situation in which the foodplant grew.
Competition between two parasites of the Florida red scale in Israel
Authors: STEINBERG SHIMON , PODOLER HAGGAI , ROSEN DAVID
Published: March 2008

ABSTRACT. 1. During the last decade, the endoparasitic wasp Pteroptrix smithi (Compere) has gradually replaced the ectoparasitic wasp Aphytis holoxanthus DeBach on the Florida red scale, Chrysomphalus aonidum (L.), on citrus in Israel. The studies reported herein were aimed at elucidating some of the mechanisms of this process.

2. Aphytis adults detected, and were attracted to hosts containing eggs of Pteroptrix, whereas adults of Pteroptrix did not detect hosts containing eggs of Aphytis. In this extrinsic aspect of host discrimination, Aphytis is superior to its competitor. Neither species responded to hosts containing heterospecific first‐instar larvae, and both tended to avoid hosts containing more advanced developmental stages of the other species.

3. Aphytis outcompeted Pteroptrix in most cases of multiple parasitism, as observed under both controlled and field conditions.

4. Aphytis was superior in mixed‐species cultures; however, its dominance was affected by the availability of adult food.

5. Aphytis adults were found to be more sensitive (×4.11) to the insecticide malathion as compared to adults of Pteroptrix. This finding provides a possible explanation to the displacement of Aphytis by Pteroptrix in the citrus groves along the coastal plain of Israel.
Variance in number of eggs per patch: oviposition behaviour and population dispersion in a seed parasitic moth
Authors: THOMPSON JOHN N.
Published: March 2008

ABSTRACT. 1. The relationship between oviposition behaviour and population dispersion was analysed for Grey a subalba Braun (Lep., Incurvariidae), a species in which females usually, but not invariably. lay eggs in only a few schizocarps (seed‐pairs) on each umbellet they visit on Lomatium dissectum (Umbelliferae). During each of four years females exhibited a constant probability of leaving an umbellet after each egg was laid. Hence, some umbellets received more eggs than others and the behaviour matched a geometric distribution of eggs among umbellets.

2. The variance in number of schizocarps attacked per umbellet by individual females did not result from females choosing schizocarps of particular sizes or avoiding schizocarps that already contained eggs or larvae. A potential, but speculative, explanation of the variance is that females distribute their eggs among umbellets in a way that maximizes unpredictability on larval dispersion to a searching parasitoid, The pattern of oviposition by Greya females fits the truncated geometric distribution that is predicted if information, as indexed by the Shannon‐Wiener entropy measure, is minimized. None the less, other measures of unpredictability or minimum information are possible, and the results highlight the problem of how to identify patterns of movement that may result from selection for unpredictability to enemies.

3. In systematic surveys of the L.dissectum population during three consecutive years, virtually all plants had between 10% and 65% of their seeds attacked. Hence, the separation of oviposition bouts between umbellets and the constant probability of leaving an umbellet after each egg was laid resulted in a broad distribution of Greya attack among L.dissectum plants.
Population density, phenotype and reproductive output in the grasshopper Chorthippus brunneus
Authors: WALL RICHARD , BEGON MICHAEL
Published: March 2008

ABSTRACT. 1. The effects of population density on the reproductive output of individual female grasshoppers (Chorthippus brunneus Thunberg) and the relationships between reproductive output and component elements of each female's phenotype, were investigated.

2. Reproductive output was primarily determined by the rate of egg‐pod production. Increased density led to significant reductions in the rate of egg‐pod production and reproductive output.

3. Exoskeleton size (reflecting nymphal experience) was positively correlated with clutch size at both high and low densities, but condition (reflecting adult experience) showed no such correlation. At high density, exoskeleton size was more strongly correlated with the rate of egg‐pod production and reproductive output than condition. It is concluded that the nymphal aspects of size are more important than the adult aspects.

4. At low density, females with small exoskeletons compensated for their smaller clutches by producing egg‐pods at a faster rate. Thus, there was no overall relationship between reproductive output and any of the phenotypic characteristics.

5. The effects of competition were weakly asymmetric in high density populations. The weakness of the asymmetry suggests scramble‐like interactions for resources. It is concluded that not only are the effects of competition influenced by individual differences, but also that competition may reveal differences that would not otherwise be apparent.
Seasonal and individual variation in gregarine parasite levels in the field crickets Gryllus veletis and G.pennsylvanicus
Authors: ZUK MARLENE
Published: March 2008

ABSTRACT. 1. Gregarines, debilitating protozoan gut parasites, were monitored in two species of field cricket, Gryllus veletis (Alexander and Bigelow) and G.pennsylvanicus Burmeister, in northern Michigan in 1983 and 1984.

2. Gregarines were found in 31–51% of G.veletis individuals and 50–70% of G.pennsylvanicus.

3. Males were more heavily infected than females in G. veleris, but G.pennsylvanicus males and females had nearly equal infection levels; this disparity resulted in an overall lower infection rate for G. veletis.

4. Both species had fewer gregarines in 1983 than in 1984, possibly due to the adverse effect of drier conditions in 1983 on development of parasite cysts in the soil.

5. Levels of infection were not constant throughout the breeding season for either cricket species.

6. Body size was not correlated with parasite load in either G. veletis or G.pennsylvanicus.

7. Adult age was unrelated to gregarine level in G. veferis, whereas G.pennsylvanicus showed a positive correlation between adult age and parasite load during two non‐consecutive weeks of the breeding season.
Role of host‐plant stimuli in sexual behaviour of small ermine moths (Yponomeuta)
Authors: HENDRIKSE ANS , VOS‐BÜNNEMEYER ELLY
Published: March 2008

ABSTRACT. 1. Studies involving experiments with olfactometers and field experiments have shown that the release of sex‐pheromone by females of Yponomeuta spp. is stimulated by the presence of host plants.

2. While in Y.evonymellus L. less females emitted pheromone in the absence of host plants, in Y.padellus L. the initiation of pheromone release was delayed.

3. Females of Y.evonymellus, Y.cagnagellus Hüb., Y.padellus and Y.plumbellus D. & S. all preferred a place with host‐plant odour to one with non‐host odours for sex‐pheromone release.

4. Male preference for host‐plant odour was demonstrated in the laboratory only for Y.cagnagellus.

5. Trap catches in the field indicated a reinforcement of female attractiveness by host‐plant stimuli.
A comparative study of the relationship between host size and brood size in Apanteles spp. (Hymenoptera: Braconidae)
Authors: Le MASURIER A. D.
Published: March 2008

ABSTRACT. 1. Current models of insect oviposition predict that clutch size in parasitoids should correlate with host size, with a continuum from solitary species at one end to large gregarious broods at the other. This prediction is tested for the genus Apanteles (sensu lato).

2. The distribution of brood sizes in Apanteles is bimodal, with peaks at one (solitary species) and at about twenty (gregarious species).

3. Brood size of gregarious species correlates with host size, but when a measure of the total volume of a parasitoid brood is plotted against host size, solitary species do not lie on the same regression slope as gregarious species.

4. There is a relative shortage of gregarious species on small hosts, and a relative excess of solitary species on large hosts. Solitary species on large hosts do not fully consume the host resource.

5. The possible role of evolutionary constraints to adaptive progeny allocation in Apanteles is discussed.
Egg hatching inhibition: field evidence for population regulation in a treehole mosquito
Authors: LIVDAHL TODD P. , EDGERLY JANICE S.
Published: March 2008

ABSTRACT. 1. We investigated the influence of larval density on egg hatching in the treehole mosquito, Aedes triseriatus Say (Diptera: Culicidae) by submerging laboratory‐produced egg batches in natural habitats stocked with fixed densities of larvae.

2. We found a significant decrease in hatching rate as larval density increased. The results suggest that inhibited eggs refrain from hatching into environments in which competitive effects of large larvae are potentially severe, and in which cannibalism may occur.

3. The amount of time the egg batches were exposed to experimental conditions (between 2 and 16 days) had no significant influence on hatch rate.
Activity budgets, habitat use and body size in two coexisting species of sand wasps (Microbembex: Sphecidae, Hymenoptera)
Authors: TOFT CATHERINE A.
Published: March 2008

ABSTRACT. 1. Two superficially similar species of Microbembex, M.monodonta (Say) and M.cubana Bohart (Hymenoptera, Sphecidae, Nyssoninae), occur syntopically on Staniel Cay, a small Bahamian island (15 km2).

2. Nesting (female) and territorial (male) aggregations of M.cubana were smaller and more numerous than those of M.monodonta in the study site and on the island as a whole.

3. Both species had regular patterns of daily activities that required them to use a variety of microhabitats in the study area.

4. Males of both species defended territories from c. 09.00 to 12.00 hours EST (in May) and the left to feed on nectar until they retired to sleeping burrows, typically from 13.00 to 15.00 hours. Male M.monodonta were active longer each day and intermixed feeding and territorial defence more than did male M.cubana.

5. Females of both species were active for longer each day, from c. 08.30 to 15.30 hours, and intermixed their respective activities – hunting for provisions, feeding, and nest digging and maintenance – during each day more than did males. Female M.monodonta were active longer each day, rising earlier and retiring later, than female M.cubana.

6. In M.monodonta, females were larger (length, X =11.00 mm) than males (10.5 mm). In M.cubana, males were larger (11.1 mm) than females (10.4 mm). Although mean differences were small, they were highly significant (F=22.42; P<10−4) for the species‐sex interaction.

7. Differences in activity budgets, habitat use, and sexual size dimorphism appear to be related. A combination of factors, particularly thermal constraints, possible competition, and different mating systems, could explain these patterns.