Parasitism by the mite Trombidium breei on four U.K. butterfly species

Abstract 1.  The incidence of parasitism by larvae of the mite species Trombidium breei was reported in one population of the lycaenid butterfly Polyommatus icarus , four populations of the satyrine butterfly Maniola jurtina , one population of the satyrine butterfly Aphantopus hyperanthus , and two populations of the satyrine butterfly Pyronia tithonus , as well as on one specimen of the dipteran Alophorus hemiptera . A considerable proportion of butterflies (11-50%) was infested in all study populations.
2. The pattern of infestation was examined in detail in M. jurtina . Males had a significantly higher incidence of infestation than females, and middle-aged butterflies had a higher incidence of infestation than old or young butterflies. The incidence of infestation peaked in the middle of the flight season, and this seasonal effect was independent of the effect of butterfly age.
3. Using a model based on capture-recapture data, it was estimated that a hypothetical ideal male M. jurtina that lives exactly the mean expected lifespan of 9-10 days has an approximately 75% chance of becoming infested with mites at least once during its lifetime, a mean time to first infestation of 3-4 days, and an average infestation persistence time of 2-3 days.
4. Capture-recapture data failed to show any effect of mite infestation on the lifespan or within-habitat movement rate of M. jurtina .
5. In experiments in which individual butterflies were taken out of their normal habitat and released, M. jurtina and P. tithonus that were infested with mite larvae did not differ from uninfested individuals in the efficiency with which they returned to suitable habitat. Thus, parasitism by T. breei larvae had no detectable effects on flight performance or orientation ability.
6. The results suggest that trombidiid mite larvae have limited potential in the biological control of insect pests.     

Reproductive variation and adult size in two co-occurring grasshopper species

ABSTRACT. 1. Egg sizes and clutch sizes of the grasshoppers Chorthippus brunneus (Thunb.) and Myrmeleotettix maculatus (Thunb.) were compared among three years and among three sites less than 1.3 km apart. Relationships between these reproductive traits and date of egg laying, body size and body condition were sought.
2. M.maculatus , the smaller species, laid fewer but larger eggs; and only the eggs of this species showed significant differences between sites and years.
3. A negative correlation between egg size and number per clutch was evident between species and years, but generally not among sites and among individuals of a population.
4. However, a hidden negative correlation between egg size and number was uncovered within populations when the relationship was examined for females of a given mature weight.
5. Variation in the number of eggs per clutch was explained statistically by a positive relationship between female body weight and egg number. Also, both interpopulation and intrapopulation comparisons revealed that for M.maculatus , but not for C.brunneus , females with long hind femurs laid large eggs.     

Life cycle, growth, mortality and production of Ephemerella major Klapalek (Ephemeroptera) in a trout stream in Belgium

SUMMARY. 1. The life cycle of Ephemerella major Klapalek in a chalk trout stream in Belgium took 1 year. Emergence was highly synchronized with a flight period from mid-May to mid-June. Tiny nymphs occurred from June to late August.
2. The mean instantaneous growth rate was high in autumn (3.6% wet wt day⁻¹), very low from November to February (0.8% wet wt day⁻¹) and high until emergence (2.3% wet wt day⁻¹); short day length seemed to be the major factor reducing growth rate during winter.
3. Mortality was close to zero during winter and 1.4—1.7% day⁻¹during other seasons. Total mortality from egg to adult was 99.6%.
4. The annual production was about 9g wet wt m⁻² year⁻¹ and the annual P/ ratio was 7.5. There was good agreement between the production values estimated by four methods. Production rate was highest in May (13 mg wet wt m⁻² day⁻¹) and zero in February.     

Flight activity of adult stoneflies in relation to weather

Abstract. 1. Dispersal of adult aquatic insects between streams may have important consequences for local and regional population dynamics, but little is known about how dispersal is affected by weather conditions.
2. The influence of meteorological variables on flight activity of adult stoneflies (Plecoptera: Leuctridae, Nemouridae, and Chloroperlidae) was investigated using Malaise traps adjacent to three upland streams in the Plynlimon area of mid Wales, U.K.
3. Numbers of adult stoneflies captured weekly in the traps were related positively to air temperature and related negatively to wind speed. Meteorological conditions during daylight showed stronger relationships with flight activity than did conditions at night.
4. There was inter-site variation in the strength of weather effects on stonefly flight. Wind speed was significant at only one site, which had higher average wind speed than the other sites.
5. Annual variation in weather conditions during adult flight periods may result in varying extent of dispersal between sites, influencing community dynamics over a wide area.     

Spatial and temporal variation in species composition of dung beetle assemblages in southern Ireland

Abstract. 1. This study attempts to identify the main community characteristics that contribute to variability in dung beetle assemblage composition and structure across a range of spatial and temporal scales.
2. Dung beetle assemblages ( Aphodius , Sphaeridium, and Geotrupes species) were monitored by dung-baited pitfall trapping at 10-day intervals during the seasonally active period at eleven sites in southern Ireland. Three of the sites were monitored over at least 2 years between 1991 and 1996.
3. Although the species composition of the above taxonomic groups was comparable among sites and years, relative abundances of component species varied considerably. Detrended correspondence analysis ordinations indicated a similar level of variability in dung beetle assemblage structure among years, and among sites ≈1–180 km apart.
4. Processes that may contribute to spatio-temporal variability in dung beetle assemblages are discussed, and strategies for future research are suggested.     

Do hypotheses from short‐term studies hold in the long‐term? An empirical test

Abstract. 1. A sequence of population estimates for two now-extinct populations of Euphydryas editha bayensis is presented. After removing biased sampling days, estimates of demographic parameters from the long-term data were used to test five hypotheses built from studies of shorter duration. Such tests of short-term conclusions are rare.
2. The long-term demographic parameters include sex ratio, mortality, dispersal, mean flight date, and duration of flight season. The two populations differed with respect to sex ratio and mean flight date, and sexes differed with respect to mortality and dispersal.
3. Three of the five hypotheses were supported directly or indirectly by patterns in the parameters. These hypotheses predict that dynamics are asynchronous over the long term, that larval mortality, not adult abundance and mortality, is the primary determinant of changes in population size, and that topography mediates larval mortality.
4. Two hypotheses were not supported or supported only in part. Flight phenology differed between the study populations as predicted, but flight order was opposite that expected from the topographic composition of each habitat. Variability in sex ratio and the occurrence of female-biased ratios in the habitat of one of the populations also suggest that previous observations of sex ratio are not generalisable.
5. Populations were extremely volatile over the study period. Removal of biased sampling days did not change basic trends or fluctuations in the data. This volatility suggests that E. editha populations residing in similar habitats may risk immediate extinction.     

Effect of regional climate warming on the phenology of butterflies in boreal forests in Manitoba, Canada

We examined the effect of regional climate warming on the phenology of butterfly species in boreal forest ecosystems in Manitoba, Canada. For the period 1971-2004, the mean monthly temperatures in January, September, and December increased significantly, as did the mean temperatures for several concurrent monthly periods. The mean annual temperature increased ≈ 0.05°C/yr over the study period. The annual number of frost-free days and degree-day accumulations increased as well. We measured the response of 19 common butterfly species to these temperature changes with the date of first appearance, week of peak abundance, and the length of flight period over the 33-yr period of 1972-2004. Although adult butterfly response was variable for spring and summer months, 13 of 19 species showed a significant (P < 0.05) increase in flight period extending longer into the autumn. Flight period extensions increased by 31.5 ± 13.9 (SD) d over the study period for 13 butterfly species significantly affected by the warming trend. The early autumn and winter months warmed significantly, and butterflies seem to be responding to this warming trend with a change in the length of certain life stages. Two species, Junonia coenia and Euphydryas phaeton, increased their northerly ranges by ≈ 150 and 70 km, respectively. Warmer autumns and winters may be providing opportunities for range extensions of more southerly butterfly species held at bay by past climatic conditions.     

Comparative phenology of four satyrine butterflies inhabiting dry grasslands in Sweden

The phenology of the satyrine butterflies Coenonympha pamphilus L., Lasiommata megera L., Hipparchia semele L. and Maniola jurtina L. was compared under seminatural conditions with Festuca ovina as the food-plant. Coenonympha pamphilus shows striking phenotypic plasticity as revealed by initiating cohorts at successive dates during the whole flight period. Growth rate is finely tuned depending on season, and larvae can hibernate in any of the three first instars, but also aestivate when 'surplus'time is available. Hipparchia semele and M. jurtina have reduced growth rates as last instar larvae at the beginning of summer. Lasiommata megera , which has an obligate bivoltine life cycle, shows the highest overall growth rate of all four species. Results suggest that egg size variation has consequences for the life cycles of these species.     

Significance of spring migration and flexibility in flight-muscle histolysis in waterstriders (Heteroptera, Gerridae)

Abstract. 1. Individuals of long-winged waterstrider (Gerridae) species were found in spring far from their breeding habitats, which indicates that they fly before reproduction.
2. Field samples and laboratory studies show that once they return to their breeding sites, many individuals of three waterstrider species ( Gerris odontogaster (Zett.), Gerris lacustris (L.) and Limnoporus rufoscutellatus (Lat.)) histolyse wing muscles and lose flight ability during their reproductive period.
3. The extent of flight-muscle histolysis varies with environmental factors. Food scarcity affects flight-muscle histolysis in G.odontogaster females. In G.Lacustris , flight-muscle histolysis was more common in the laboratory than in the field samples. Proportionately more females than males lost their flight ability by the end of the reproductive period.
4. Flight ability had direct costs in reproductive potential with (non-flyer) females, which histolysed their flight muscles, laying more eggs than (flyer) females, which maintained flight ability. This was also the case during food scarcity. Non-flyer males of G.odontogaster survived longer than flyer males.
5. Spring migration was distinguished from dispersal during the reproductive period, because these flights serve different functions. Flight-muscle histolysis of females during reproduction is a qualitative reproductive option, with a trade-off between dispersal ability and reproductive potential. Ability to change reproductive behaviour depending on environmental conditions increases an individual's ability to cope with a large variety of habitats.     

Diurnal activity patterns in hoverflies (Diptera, Syrphidae)

Abstract. 1. Time-budgets are constructed from censuses of hoverflies. Larger species spend less time in flight.
2. Most species are active under similar conditions of light intensity, but a shade-tolerant (Melanostoma scalare Fabr.) and a sun-loving species (Metasyrphus corollae Fabr.) were identified.
3. Large species become active (i.e. move, by flying or feeding) at lower temperatures than small ones, except M.scalare, which is tolerant to cool temperatures. This means that, M.scalare apart, the order of species appearing during the day is size-dependent, largest first.
4. Previous claims about the diel periodicity of syrphids can be reconciled by considering the importance of individual thermal balance.
5. Tolerance to low temperatures in small hoverflies is associated with feeding on anemophilous pollen; this may indicate a proline-fuelled flight.     

Movement of two grassland butterflies in the same habitat network: the role of adult resources and size of the study area

Abstract. 1.  Movement patterns of two butterfly species (meadow brown Maniola jurtina L. and scarce copper Lycaenae virgaureae L.) were studied in a 172 ha area within a landscape with a high percentage of suitable habitats for mark–release–recapture experiments.
2.  Adult resource density, but not patch size or larval food plant abundance, influenced the numbers and the fractions of residents, emigrants, and immigrants.
3.  Differences between species were observed in movement frequency and maximum distances moved but not in mean distances moved.
4.  The scarce copper showed much greater movement ability than expected from the results of published studies. This is believed to be a result of the comparatively large size of the study area and the high cover of suitable habitat (>50%).
5.  The mean and maximum distances travelled by butterflies reflected differences in the size of the study area.     

Spatial patterns, temporal variability, and the role of multi-nest colonies in a monogynous Spanish desert ant

Abstract 1. The colonies of the Spanish desert ant Cataglyphis iberica are polydomous. This study describes the temporal and spatial patterns of the polydomy in this species at two different sites, and presents analyses of its role in reducing the attacks of the queen over sexual brood, and in allowing better habitat exploitation.
2. The spatial distribution of nests was clumped while colonies were distributed randomly. Mean nearest neighbour distance ranged from 3.4 to 7.0 m for nests and from 12.3 to 14.1 m for colonies. Distance of foragers searching for food varied among nests: mean values were between 6.1 and 12.6 m.
3. At both sites, the maximum number of nests per colony occurred in summer, during the maximum activity period of the species. Colonies regrouped at the end of this period but overwintered in several nests.
4. Nest renewal in C. iberica colonies was high and showed great temporal variability: nests changed (open, close, re-open) continuously through the activity season and/or among years. The lifetime of up to 55% of nests was only 1–3 months.
5. Polydomy in C. iberica might decrease the interactions between the queen and the sexual brood. In all colonies excavated just before the mating period, the nest containing the queen did not contain any virgin female. Females were in the queenless nests of the colony.
6. The results also suggest that polydomous C. iberica colonies may enhance habitat exploitation because foraging activity per colony increases with nest number. The relationship between total prey input and foraging efficiency and number of nests per colony attains a plateau or even decreases after a certain colony size (four to six nests). This value agrees with the observed mean number of nests per colony in C. iberica .     

Genetic diversity in butterflies: Interactive effects of habitat fragmentation and climate-driven range expansion

Some species are expanding their ranges polewards during current climate warming. However, anthropogenic fragmentation of suitable habitat is affecting expansion rates and here we investigate interactions between range expansion, habitat fragmentation and genetic diversity. We examined three closely related Satyrinae butterflies, which differ in their habitat associations, from six sites along a transect in England from distribution core to expanding range margin. There was a significant decline in allozyme variation towards an expanding range margin in Pararge aegeria, which has the most restricted habitat availability, but not in Pyronia tithonus whose habitat is more widely available, or in a non-expanding 'control species' (Maniola jurtina). Moreover, data from another transect in Scotland indicated that declines in genetic diversity in P. aegeria were evident only on the transect in England, which had greater habitat fragmentation. Our results indicate that fragmentation of breeding habitats leads to more severe founder events during colonization, resulting in reduced diversity in marginal populations in more specialist species. The continued widespread loss of suitable habitats in the future may increase the likelihood of loss of genetic diversity in expanding species, which may affect whether or not species can adapt to future environmental change.     

Temporal trends in phenology of the honey bee Apis mellifera (L.) and the small white Pieris rapae (L.) in the Iberian Peninsula (1952–2004)

Abstract.  1. The first adult appearance of two insect species, the honey bee Apis mellifera (L.) and the small white Pieris rapae (L.), was examined between 1952 and 2004 in Spain.
2. After factoring out the variability resulting from the broad geographical and topographical range of the 798 sampling localities, multiple regression models were used to detect temporal trends in phenology.
3. The best models were repeated, including spring temperature as the explanatory variable to examine the effects of climate on appearance phenology.
4. Both species showed similar temporal trends, delaying their appearance phenology until the mid-1970s and advancing it since that time.
5. The appearance times for both species were negatively related to mean temperature between February and April, with both species appearing earlier in years with warmer springs.
6. The strong dependence of appearance dates on temperature indicates that climatic fluctuations are primarily responsible for the inter-annual variability in spring appearance phenology of both species, and consequently account for the observed long-term trends.
7. This study demonstrates that insect phenology is an accurate and sensitive bioindicator of climate change.     

Reproductive cost of flight capability: a comparison of life history traits in wing dimorphic planthoppers

Abstract. 1. Reproductive costs associated with flight capability were evaluated in the wing dimorphic planthopper, Prokelisia dolus Wilson, by comparing the life history of traits of winged (macropterous) and flightless (brachypterous) females under controlled laboratory conditions.
2. Macropters with large thoraces and fully developed wings maintain a greater investment in flight apparatus than brachypters with small thoraces and reduced wings.
3. Associated with greater flight capability in the macropter of P.dolus are shorter adult life, decreased total fecundity, and delayed age at first reproduction compared to brachypterous females.
4. Under field conditions where mortality is high, the difference in realized fecundity between the two wing forms living on similar resources is further exaggerated with the brachypter having the greater advantage.
5. When the life history traits of the wing forms of P. dolus are compared with traits for nine other species of planthoppers, two similarities emerge. First, the preoviposition period of the macropterous wing form is always longer than that for the brachypter resulting in a reproductive delay. Second, most studies show that macropters are less fecund than brachypters.
6. There is no general tendency among planthopper species for macropterous adults to live fewer days or develop more slowly as nymphs compared to their flightless counterparts.
7. The reproductive delay and reduced fecundity of the volent wing form of planthoppers supports the notion that flight capability is costly and that phenotypic trade-offs between flight and reproduction exist.     

Interrelations Among Habitat Use, Behavior, and Flight-Related Morphology in Two Cooccurring Satyrine Butterflies, Maniola jurtina and Pyronia tithonus

Mobility, activity patterns, habitat use, and some morphological traits of two often cooccurring satyrine butterflies of grasslands—the meadow brown (Maniola jurtina) and the hedge brown (Pyronia tithonus)—were studied by a mark-release-recapture method at two sites. Additionally, someflight-related morphological traits of a series of collected females of P. tithonus were compared between recently colonized and permanent populations. The more active, but less mobile P. tithonus got faster wing damage than did M. jurtina and had more, and more symmetrically spread eyespots onthe wings. For both species, the microdistribution was affected by shelter, long vegetation, and nectar, but this was more pronounced in P. tithonus. It is hypothesized that P. tithonus may traverse the same landscape at a slower rate than M. jurtina.     

Seasonal emergence, host-seeking activity, age composition and reproductive biology of the mosquito Aedes punctor

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.     

Spatial variation of water temperature characteristics and behavior in a Devon river system

SUMMARY. 1. The results of 5 years of continuous monitoring of river water temperatures at seventeen stations within the Exe basin, Devon, U.K., are presented and discussed.
2. Systematic spatial variation in mean annual water temperature was evident and was strongly related to the topographic variable of elevation. Deviations from this relationship reflect local influences of vegetation shading, runoff source and channel character.
3. Considerable spatial variation in temperature extremes was also apparent, and the Exe basin differs from several other British river systems in exhibiting highest peak temperatures at downstream sites on the mainstream. Discharge from Wimbleball Reservoir exerted a significant influence on annual maxima and minima.
4. A clear seasonal cycle characterized all stations and was objectively defined by second-order harmonic functions which varied in amplitude and phase across the study area. Marked spatial variability in the magnitude and timing of diurnal temperature fluctuations, in temperature duration curves and in accumulated temperatures was also recorded.
5. The implications of the spatial variation in thermal regime for the growth of brown trout was also investigated.     

The evolutionary significance of bimodal emergence in the butterfly, Maniola jurtina (Lepidoptera: Satyrinae) (L.).

Most temperate butterflies exhibit a tightly synchronized unimodal adult emergence to facilitate mate location. Exceptions are presumably subject to unusual selection pressure. This study examines the pattern of emergence in Maniola jurtina , which was found to exhibit both unimodal and bimodal emergence patterns at different sites in south-east England. The bimodal pattern was found on chalk grassland; elsewhere the emergence was unimodal. Adults from each emergence peak rarely meet, suggesting that there may be some degree of reproductive isolation. Morphological measurements and electrophoretic analysis of allozyme frequencies are carried out to quantify differentiation between emergence peaks. Captive stock was reared to examine differences in the immature stages. Butterflies from each emergence differ significantly in most morphological variables measured, those from the second peak tending to be smaller. The immature stages differ in morphology and longevity of the egg stage. Allozyme frequencies did not differ between peaks, suggesting that they are not reproductively isolated. Explanations for the maintenance of differences between emergence peaks despite gene flow are discussed. I propose that division of offspring between two emergence times may have evolved to avoid the risk inherent in placing all offspring in one peak which may be rendered inviable by temporal fluctuations in habitat quality.     

A 9-year study of the life cycle of Ephemera danica Müll. (Ephemeridae: Ephemeroptera) in the River Lambourn, England

Abstract. 1. The life cycle of the mayfly, Ephemera danica , was studied on two contrasted sites on the River Lambourn between 1971 and 1979.
2. Quantitative samples of nymphs were taken on the five major biotopes of the river bed, gravel, silt, Ranunculus, Berula and Callitriche . Exposed areas of gravel and silt held significantly lower densities of nymphs than the three macro-phytes with their underlying substrata. The sandy substratum underlying beds of Berula frequently held significantly higher densities than the other macrophytes.
3. Monthly samples from March 1971 to April 1972 followed by samples in June and December from 1972 to 1979 indicated that the nymphal phase normally took 2 years in the River Lambourn.
4. All odd-numbered years from 1971 to 1979 produced weak year-classes. In contrast, all even-numbered years between 1970 and 1978, with the exception of 1972, produced relatively strong year-classes.
5. Meteorological data for the period of flight activity in E.danica indicated that conditions were colder and damper in 1972 than in the other even-numbered years of the study, when recruitment was more successful.