An attempt at re-establishing the swallowtail butterfly at Wicken Fen

Abstract.

• 1 Details of a reintroduction of the swallowtail, Papilio machaon, to Wicken Fen are given.
• 2 The introduced population expanded at first, but crashed as a result of the 1976 drought. It then failed to recover and is probably now again extinct on the Fen.
• 3 The changes in the habitat and the status of the butterfly's food plant, Peucedanum palustre, caused by the drying out of the Fen are discussed, and it is concluded that there is no chance of reestablishing the butterfly permanently at Wicken, unless the Fen can be made wetter.

     

The ecology and status of Thymelicus acteon (Lepidoptera: Hesperiidae) in Britain

ABSTRACT.

• 1 A survey was made of the local butterfly, the Lulworth Skipper (Thymelicus acteon Rott.) in Britain. Adult numbers were estimated on most sites and the habitat was analysed. Changes in numbers were also recorded in five populations over 6 years, and some aspects of behaviour were studied.
• 2 T.acteon forms closed populations. It was found in great abundance throughout its historical range, and appears both to have increased in numbers and to have spread locally. It has not extended its range.
• 3 The wrong larval foodplant is quoted by some modern textbooks. T.acteon requires mature Brachypodium pinnatum Beauv. plants for breeding. Within its range, the butterfly was almost ubiquitous in areas with tall Brachypodium.
• 4 The present abundance and probable increase of T.acteon is attributed to the spread of B.pinnaturn in unimproved calcareous grassland. This has occurred through a decline in grazing, both by domestic stock and, since myxomatosis, by rabbits.

     

Mechanical thinning to restore oak savanna promoted predator assemblages of gypsy moth pupae in Michigan

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Temporal and geographic variation in parasitoid attack with no evidence for ant protection of the Melissa blue butterfly,Lycaeides melissa

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Calculation of collated indices of abundance of butterflies based on monitored sites

Abstract.

• 1 The Butterfly Monitoring Scheme uses regular transect counts on fixed sites to establish annual indices of abundance of butterfly species in the United Kingdom. The annual change in collated index for each species has hitherto been calculated as a simple ratio between total counts summed over all participating sites.
• 2 A revised method for calculation of collated indices is proposed, which applies a logarithmic transformation to site values so as to downweight the influence on the index of the sites with greatest numbers of a species. Zero counts are handled comparably with non-zero values. An alternative method using geometric mean ratios is also examined.
• 3 Indices calculated using the logarithmic transformation are compared with those calculated using the traditional method. Two internal tests of dependency of collated indices on the sites with highest abundance are made. Another evaluation uses regression analysis for the effects of temperature and rainfall on collated indices of butterfly abundance.
• 4 The first internal test shows that logarithmic transformation reduces the dependence of the collated index on the sites of highest abundance for twenty-five out of twenty-seven species examined; while a second test shows a reduction for twenty-six out of forty-two species, and an increase for one species. The number of significant regressions on temperature variables increases with the use of the logarithmic transformation from 11% to 13% of tests made, and on rainfall from 10% to 11%.
• 5 The geometric mean ratio method introduces considerable biases in its treatment of zero values, for which a remedy is not available.
• 6 Although the revised collated indices calculated using logarithmic transformation are broadly comparable with traditionally calculated values, the reductions in dependency on sites with the most abundant populations render the revised indices less subject to perturbation due to local ‘noise’, and so more suitable for research on factors influencing butterfly abundance.

     

Flight endurance in relation to adult age in the green‐veined white butterfly Pieris napi

• 1 The flight apparatus in butterflies, as well as in other insects, is costly to manufacture. Since most animals live in a world where resources are limited, trade‐offs are expected and available resources must thus be allocated between flight and other functions, such as reproduction.
• 2 To mitigate this trade‐off, previous studies have shown that butterflies can break down flight muscles in the thorax as they age in order to use muscle nutrients for reproduction.
• 3 Although breakdown of flight muscles is expected to reduce flight ability, relative flight muscle mass (thorax mass/body mass) in many butterfly species does not decrease with age. The aim of the present study was to test the relationship between flight endurance and adult age in the green‐veined white butterfly Pieris napi (L.). The tests were performed in the laboratory at five different temperatures.
• 4 The results showed that age has a significant influence on butterfly flight endurance; older butterflies showed reduced flight endurance. Male butterflies fly for a longer time than females and flight endurance increases with temperature in both sexes.

     

Oviposition preference and larval performance of the sweet potato butterfly Acraea acerata on Ipomoea species in Ethiopia

• 1 The sweet potato butterfly Acraea acerata is an indigenous species in Ethiopia that has become a major pest on the introduced sweet potato Ipomoea batatas. To assess the role of wild Ethiopian Ipomoea species as host plants, the presence of larvae on wild ipomoeas was studied, and female oviposition choice and larval performance were tested on five wild ipomoeas, as well as on sweet potato.
• 2 In laboratory tests, oviposition and larval development were successful on two wild ipomoeas (Ipomoea tenuirostris and Ipomoea cairica) but no oviposition occurred on the remaining three species. Of the latter, larvae did not feed on Ipomoea hochstetteri and Ipomoea indica, and survival rates were extremely low on Ipomoea purpurea.
• 3 Sweet potato was a better host plant than I. tenuirostris and I. cairica in terms of oviposition preference, larval survival and pupal size; pupae were larger, resulting in more fecund female butterflies.
• 4 In the wild butterfly populations were abundant on I. tenuirostris but absent on I. cairica. Females also tended to prefer I. tenuirostris to I. cairica in oviposition choice experiments. However, no significant differences in performance were found between larvae raised on I. tenuirostris and I. cairica in the laboratory.
• 5 Wild populations of A. acerata also existed on Ipomoea obscura, a plant not investigated in the present study.
• 6 The abundance of A. acerata on wild ipomoeas is too low to likely affect butterfly population densities on sweet potato. However, wild populations may act as reservoirs subsequent to butterfly population bottlenecks on sweet potato.

     

Aridity could have driven the local extinction of a common and multivoltine butterfly

1. Identifying which species are being negatively impacted by climate change and the mechanisms driving their decline is essential to effectively protect biodiversity.
2. Coenonympha pamphilus is a common and generalist butterfly, widely distributed throughout the Western Palearctic, being multivoltine in southern Europe. Previous studies indicate that it will not be substantially affected by climate change; however, it has seemingly disappeared from the southeast of the Iberian Peninsula in the last decades.
3. Here, we aim to determine if it has effectively disappeared from this area, as well as identify the environmental conditions limiting its distribution and the potential causes behind this a priori local extinction.
4. We downloaded all the occurrence records of C. pamphilus and analysed their spatial and temporal trends. To identify the climatic variables driving the distribution of this butterfly in the Iberian Peninsula, we performed an ensemble species distribution model (SDM), combining 600 individual models produced with 6 algorithms.
5. We confirmed that C. pamphilus has not been observed in the southeast of the Iberian Peninsula since 2008. Aridity was the main factor limiting the distribution of C. pamphilus in our ensemble SDM, with areas with high aridity being unsuitable for this species.
6. We hypothesise that multivoltinism is the mechanism driving this local extirpation, as high aridity is causing host plants (Poaceae) to wither prematurely, precluding the development of the second and/or third generations of the butterfly. Even though generalist species are theoretically more resilient to climate change, other traits such as multivoltinism may increase their vulnerability and need to be further investigated.

     

Effects of polyculture and monoculture farming in oil palm smallholdings on tropical fruit‐feeding butterfly diversity

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Habitat loss and degradation due to farming intensification modify the floral visitor assemblages of a semiarid keystone shrub

1. The expansion of intensive agriculture has severely altered landscapes, a process that has been aggravated by the increase of greenhouse agriculture. However, few studies have considered the combined effects of habitat loss/degradation and greenhouse farming on insect visitors to native plants.
2. We analysed how habitat loss/degradation and greenhouse farming are related to the composition, abundance, and richness of the insect assemblages visiting flowers in a semiarid keystone shrub (Ziziphus lotus) in southeast Spain, home to Europe's largest area of greenhouses. We studied 21 populations distributed across a gradient of greenhouse intensification and habitat loss.
3. The composition, abundance, and richness of the Ziziphus insect assemblage substantially varied between populations and were differently affected by natural habitat-remnant and landscape degradation and population isolation.
4. Insect abundance was negatively affected by habitat loss at population level but positively affected at individual Ziziphus scale. Honey-bee relative abundance increased in highly degraded landscapes and isolated populations, being positively associated with hoverflies and negatively with ants and bee-flies. Wild bees, carrion flies, and wasps remain neutral along the degradation axes. Insect visitor abundance per plant affected positively the flower visitation rate, which was also favoured by the relative abundance of honey bees, wild bees, and hoverflies. Species richness was not influenced by anthropogenic degradation, and did not affect flower visitation rate.
5. Our results highlight the fragility of wild pollinator communities to landscape and habitat degradation, and the need to regulate intensive farming practices to preserve wild insect pollinator assemblages in semiarid habitats.

     

Micro‐climate determines oviposition site selection and abundance in the butterfly Pyrgus armoricanus at its northern range margin

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Possible Metapopulation Structure of the Threatened ButterflyPyrgus armoricanus in Sweden

Many insect species dependent on patchily distributed habitats have been shown to exist as metapopulations. Here I investigated the occurrence patterns of the butterfly Pyrgus armoricanus at its northern range margin in Sweden. This was done by mapping all potentially suitable habitat patches within the only area in Sweden where the species occurs (ca. 10├ù20┬ákm), and thereafter checking for presence of the butterfly in all these patches. P. armoricanus was found in 15 patches of dry grassland with presence of one of its potential larval host plants. Both the probability of occurrence and local abundance increased with patch area and decreased with increased isolation. Local abundance was positively related to the presence of an additional host plant. The results support the hypothesis that the persistence of P. armoricanus in Sweden is dependent on metapopulation dynamics. However, further studies, both on dispersal ability and on habitat requirements are needed before this can be ascertained.     

Determinants of foraging profitability in two nectarivorous butterflies

ABSTRACT.

• 1 I studied flower selection and foraging energetics of Agraulis vanillae L. (Nymphalidae) and Phoebis sennae (Pieridae), two butterfly species common to north central Florida. I identified the major nectar resources exploited by several populations of these butterflies and, for each plant species, measured available nectar volumes and concentrations, corolla lengths, and density. I quantified foraging behaviour of each butterfly species at each nectar source (flower visitation rate and percentage of foraging time in flight), and used these data to estimate the net rate of energy intake of each butterfly species at each nectar source.
• 2 Estimated mean energy contents of individual flowers of the eleven exploited plant species spanned three orders of magnitude, ranging between 0.015 and 9.27 joules. Mean energy content of individual flowers was strongly correlated with mean foraging profit of both butterfly species.
• 3 Mean nectar volume strongly influenced energy content and varied widely within and among species, ranging from 0.0076 to 1.853 μ1. Nectar concentration varied between 17.1% and 40.4% sucrose-equivalents. Nectar volume was the best single predictor of foraging profitability (correlation coefficients of 0.994 and 0.984 for Phoebis and Agraulis respectively). Corolla length also strongly affected foraging profitability for both butterfly species; flower species with longer corollas were generally more profitable.
• 4 Flower density and nectar concentration showed weak or nonsignificant associations with foraging profitability.
• 5 The usefulness and limitations of these floral characteristics as bases for foraging selectivity, and the selective pressures foraging butterflies might place on the visited plants are discussed.

     

Ants climb plants because they cannot swim: ant presence on flowers during the flood season reduces the frequency of floral visitors

1. Seasonal changes in environments may not only affect habitat connectivity but may also affect its use by species and their interactions. Thus, during the flood season, ants are forced to develop survival strategies such as vertical plant migration.
2. According to this, it has been hypothesized that the presence of ants may directly affect plant-pollinator interactions.
3. Thus, we asked the following questions: (i) Are floral visitors of Hyptis brevipes expelled due to ant presence on inflorescences during the flood period? (ii) Is the ant effect mediated by the abundance of ants foraging on inflorescences? And, (iii) Does flower abundance predict the abundance of floral visits and ants?
4. We experimentally sampled 59 H. brevipes plants with and without ants during the flooded season, and observed no differences in flower abundance between ant treatments.
5. The probability of detaining floral visitors on H. brevipes increased with ant abundance and exceeded 50% possible repellency, but the probability of visitor deterrence was not related to flower abundance. Furthermore, the abundance of flowers did not predict the number of ants on H. brevipes individuals or the frequency of floral visits.
6. Consequently, ant repelling effects are pronounced when there are more ants foraging on plants. However, the ant repelling effect can be mitigated when plants flourish all year-round and exhibit higher concentrations of flowers in the dry months. Additionally, the different sexual functions of plants may present specific responses due to the explosive pollination mechanism associated with ant effects.

     

The African golden cat Caracal aurata: Africa's least‐known felid

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Interspecific competition between insect herbivores: asymmetric competition between cinnabar moth and the ragwort seed-head fly

ABSTRACT.

• 1 Removal field experiments and observational studies have been undertaken to determine whether feeding by cinnabar moth Tyria jacobaeae L. on the flower heads of ragwort Senecio jacobaea L. affects the abundance of the fly Pegohylemyia seneciella (Meade) that feeds in the flower heads as a larva.
• 2 Correlations between the population density of cinnabar moth and the population density of the fly were suggestive of habitat separation, but provided little evidence of exploitation competition.
• 3 Removal of cinnabar moth by hand from replicated plots over two years shows that, in years when ragwort flower production is consumed by cinnabar moth caterpillars, the fly may show no recruitment at all.
• 4 Fly populations persist in refugia, exploiting ragwort plants that grow in areas where there are no cinnabar moth.
• 5 Recruitment of ragwort is not seed limited, so the reduction in seed production caused by P. seneciella (maximum about 30%) has no impact on ragwort abundance, or on the abundance of cinnabar moth.
• 6 We conclude that there is strong interspecific competition between these two species, and that the competition is highly asymmetric. The cinnabar moth had a substantial effect on the recruitment of the fly in 1986, but the fly has no measurable impact on the recruitment of the moth. In six years out of seven in our long-term study, cinnabar moth reduced flower production to levels comparable to those measured in 1986, and we infer that strong competition with the fly was likely in six years out of seven.
• 7 One reason why there are so few published examples of asymmetric interspecific competition may be simply that the experiments are thought too obvious to be worth doing. We argue that this is not a good reason for eschewing manipulative field experiments, and that few processes in ecology are at all obvious when investigated in detail.

     

Littoral microcrustacea in Lake 302S in the Experimental Lakes Area of Canada: acidification and recovery

• 1 The littoral microcrustacean community (Cladocera and Copepoda) was examined from 1989 to 1991 in a lake experimentally acidified to pH 4.5, and from 1992 to 1997 during the early stages of pH recovery.
• 2 Cladoceran abundance declined significantly from 1989 to 1991 (pH 4.5), but species richness did not change. Acantholeberis curvirostris, Simocephalus serrulatus, Latona spp. (Latona setifera, L. parviremis), and all species of chydorid Cladocera declined markedly in abundance while at pH 4.5. The abundance of cyclopoid copepods was low and Ceriodaphnia and calanoid copepods were absent.
• 3 Recovery of the community was subsequently monitored as pH was incrementally changed to a target pH 5.1 in 1992 and 1993, and to 5.8 in 1994–97. Species richness remained unchanged. Chydorid cladocerans remained at low abundance in 1992, and only Chydorus cf. brevilabris increased substantially from 1993 to 1996. Non‐chydorid Cladocera increased in abundance in 1992, declined again in 1993, then gradually increased (mainly due to Ophryoxus gracilis) in 1994–96. All species declined in 1997 as minnows recolonized the lake. The calanoid copepod Leptodiaptomus minutus was present in low numbers in 1997.
• 4 The microcrustacean community in the littoral zone of Lake 302S has not yet shown consistent signs of recovery from acidification.

     

Delayed ovarian maturation in the butterfly Hipparchia semele as a possible response to summer drought

ABSTRACT.

• 1 Several references indicate that the period of flight of the European satyrine butterfly Hipparchia semele (L.) (Nymphalidae, Satyrinae) starts earlier in southern latitudes, where summers are longer and drier than in the north. However, summer drought has an adverse effect on the growth of grasses on which larval feeding depends. Growth of the grasses is delayed as long as the drought lasts.
• 2 From laboratory and field observations in a mid altitude area near the centre of the Iberian Peninsula, a mechanism that can be interpreted as an adjustment of this insect's life cycle to the host plant's phenology has been observed, i.e. delayed gonadal maturation of adult females. This delay is not associated with female diapause. Although the mean delay in oviposition after copulation was 43 days some captive females were able to oviposit much earlier, and this suggests variability in oviposition dates which might have an environmental or a genetic basis.
• 3 A mechanism of delayed ovarian maturation similar to that of H.semele is also known to occur in the satyrine Maniola jurtina (L.); it is suggested that this adaptation enables these species to occupy wider geographical ranges than other univoltine satyrines in Europe.

     

Environmental DNA analysis for estimating the abundance and biomass of stream fish

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Abundance–occupancy patterns in a riverine fish assemblage

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