EXPERIMENTAL ANALYSES OF WING SIZE,FLIGHT, AND SURVIVAL IN THE WESTERN WHITE BUTTERFLY

Butterflies have distinctively large wings relative to body size, but the functional and fitness consequences of wing size for butterflies are largely unknown. I use natural and experimentally generated variation in wing surface area to examine how decreased wing size affects flight and survival in a population of the western white butterfly, Pontia occidentalis. In the laboratory, experimental reductions in wing area (reduced-wings manipulation) significantly increased wingbeat frequencies of hovering butterflies, whereas a control manipulation had no detectable effects. In contrast, behavioral observations and mark-release-recapture (MRR) studies in the field detected no significant differences in flight activity, initial dispersal rates, or recapture probabilities among treatment groups. Estimated selection coefficients indicated that natural variation in wing size, body mass, and wing loading in the population were not significantly correlated with survival in the two MRR studies. In two mark-recapture studies with manipulated butterflies, survival probabilities were not significantly different for reduced-wings individuals compared with control or unmanipulated individuals. In summary, experimental reductions in wing area significantly altered aspects of flight in the laboratory, but did not detectably alter flight or survival in the field for this population. The large wing size typical of butterflies may reduce the functional and survival consequences of wing size variation within populations.     

Habitats and Resources: The Need for a Resource-based Definition to Conserve Butterflies

Current definitions of habitat are closely allied to the concept of patch and matrix. This concept is, for instance, central to the prevailing metapopulation models of population dynamics. But, butterfly population dynamics, mobility and spatial structure can only properly be understood in the context of a resource-based definition of habitats. In criticising current definitions of habitat, we illustrate how habitat is best understood in terms of resource distributions. These transcend vegetation-based definitions of habitat and lie at the root of life history strategies, the vulnerability of butterflies to environmental changes and extinction, and govern conservation status. We emphasise the need for a resource-use database and demonstrate the shortcomings of current data for conserving butterflies; patch based definitions of habitats are inappropriate for some species and for others do not provide a universal panacea, inadequately explaining spatial occurrence when scaled over space and time. A resource-based habitat definition challenges the bipolar, patch vs. matrix view of landscape; the alternative is to view landscape as a continuum of overlapping resource distributions. We urge greater attention to the details of butterfly behaviour and resource use as the keys to understanding how landscape is exploited and therefore to successful conservation at the landscape scale.     

Spatial ecology of host–parasitoid interactions: a threatened butterfly and its specialised parasitoid

Habitat conservation for threatened temperate insect species is often guided by one of two paradigms: a metapopulation approach focusing on patch area, isolation and number; or a habitat approach focusing on maintaining high quality habitat for the focal species. Recent research has identified the additive and interacting importance of both approaches for maintaining populations of threatened butterflies. For specialised host-parasitoid interactions, understanding the consequences of habitat characteristics for the interacting species is important, because (1) specialised parasitoids are particularly vulnerable to the consequences of fragmentation, and (2) altered interaction frequencies resulting from changes to habitat management or the spatial configuration of habitat are likely to have consequences for host dynamics. The spatial ecology of Cotesia bignellii, a specialist parasitoid of the threatened butterfly Euphydryas aurinia, was investigated at two spatial scales: within habitat patches (at the scale of individual aggregations of larvae, or ‘webs’) and among habitat patches (the scale of local populations). Parasitism rates were investigated in relation to larval web size, vegetation sward height and host density. Within patches, the probability of a larval webs being parasitized increased significantly with increasing number of larvae in the web, and parasitism rates increased significantly with increasing web isolation. The proportion of webs parasitized was significantly and negatively correlated with cluster density. Among habitat patches the proportion of parasitized webs decreased as cluster density increased. Clusters with a high proportion of larval webs parasitized tended to have lower parasitism rates per larval web. These results support the call for relatively large and continuous habitat patches to maintain stable parasitoid and host populations. Conservation efforts directed towards maintenance of high host plant density could allow E. aurinia to reduce parasitism risk, while providing C. bignellii with sufficient larval webs to allow population persistence.     

Adult demography of an isolated population of the threatened butterfly Scarce Heath <Emphasis Type="Italic">Coenonympha hero</Emphasis> and its conservation implications

Scarce Heath Coenonympha hero is considered to be one of the most seriously threatened European butterflies, especially declining in western and central Europe. It usually occurs in small, discrete colonies forming metapopulation systems, but the exchange of individuals between habitat patches is considered limited. Therefore the persistence of the species in fragmented systems is likely to depend largely on the demography of local populations. We investigated a highly isolated population of the species in Poland with mark-release-recapture (MRR). The seasonal population size was assessed at 168 adults, with a well balanced sex ratio. The slightly higher capture probability of females that we recorded is quite atypical for butterflies and may be related to the vegetation structure at the site. The flight period was relatively short (22 days), and the adult life span was estimated at 6.59 days, i.e., twice as long when compared with adult longevity in two other threatened Coenonympha species. Consequently, the temporal fragmentation index (i.e., the ratio of flight period length to adult life span) was calculated at 3.3, which is the lowest value recorded among all congeneric species, suggesting that temporal fragmentation is not a major problem in the investigated population. Nevertheless, the population may be at risk of extinction due to its small size and isolation. Moreover, the area of C. hero habitat has decreased considerably over the last decade due to afforestation. Our findings indicate the need for immediate conservation actions, in particular for the removal of tree seedlings that encroach on the butterfly habitat.     

The impact of habitat fragmentation on trophic interactions of the monophagous butterfly <Emphasis Type="Italic">Polyommatus coridon</Emphasis>

Theory predicts that habitat fragmentation, including reduced area and connectivity of suitable habitat, changes multitrophic interactions. Species at the bottom of trophic cascades (host plants) are expected to be less negatively affected than higher trophic levels, such as herbivores and their parasitoids or predators. Here we test this hypothesis regarding the effects of habitat area and connectivity in a trophic system with three levels: first with the population size of the larval food plant Hippocrepis comosa, next with the population density of the monophagous butterfly species Polyommatus coridon and finally with its larval parasitism rate. Our results show no evidence for negative effects of habitat fragmentation on the food plant or on parasitism rates, but population density of adult P. coridon was reduced with decreasing connectivity. We conclude that the highly specialized butterfly species is more affected by habitat fragmentation than its larval food plant because of its higher trophic position. However, the butterfly host species was also more affected than its parasitoids, presumably because of lower resource specialization of local parasitoids which also frequently occur in alternative hosts. Therefore, conservation efforts should focus first on the most specialized species of interaction networks and second on higher trophic levels.     

Nectar and hostplant scarcity limit populations of an endangered Oregon butterfly

As grassland habitats become degraded, declines in juvenile and adult food resources may limit populations of rare insects. Fender's blue butterfly (Icaricia icarioides fenderi), a species proposed for listing as endangered under the US Endangered Species Act, survives in remnants of upland prairie in western Oregon. We investigated the effects of limited larval hostplants and adult nectar sources on butterfly population size at four sites that encompass a range of resource densities. We used coarse and detailed estimates of resource abundance to test hypotheses relating resource quantity to population size. Coarse estimates of resources (percent cover of hostplant and density of nectar flowers) suggest that butterfly population size is not associated with resource availability. However, more detailed estimates of resources (density of hostplant leaves and quantity of nectar from native nectar sources) suggest that butterfly population size is strongly associated with resource availability. The results of this study suggest that restoring degraded habitat by augmenting adult and larval resources will play an important role in managing populations of this rare butterfly. Received: 20 June 1998 / Accepted: 25 November 1998     

Evolutionary responses by butterflies to patchy spatial distributions of resources in tropical environments

The greatest diversity of butterflies and their host plants occurs in tropical regions. Some groups of butterflies in the tropics exhibit monophagous feeding in the larval stage, exploiting only one family of plants; others are polyphagous, feeding on plants in two or more distinct families. The two major types of tropical habitats for butterflies, namely primary and secondary forests, offer very different evolutionary opportunities for the exploitation of plants as larval food. Butterflies are faced with the major logistical problem, as are many other herbivorous insects, of depositing eggs on the correct plant for successful larval feeding. This paper, using the concepts of phenotype set and spatial patchiness of resources, attemps to make some predictions as to the optimal phenotypic systems for monophagous and polyphagous feeding in tropical butterflies, as related to the spatial patchiness of larval host plants in primary and secondary forests. In addition to the secondary compound chemistry of larval host plants as playing a role in the evolution of monophagy and polyphagy, the assumption is made that the spatial patchiness of host plants within and among different families also acts as a major factor in determining optimal ranges of phenotypes for different patterns of larval feeding. Owing to the high spatial patchiness of primary forest species of canopy trees and vines, it is predicted that butterflies exploiting these will be mostly polyphagous, whereas secondary forests having stable formations of fewer plant species and larger patches of these plants, will have mostly monophagous species. Forest understories may have both monophagous and polyphagous species, depending upon the layer of forest and the general type of understory (i.e. palmaceous or dicotyledonous). Field data on some groups of butterflies from tropical America support these predictions. Polyphagous butterflies are predicted to possess a genetic system of mixed morphs with a population being polymorphic as a whole; monophagous butterflies are predicted to have individuals all more or less similar genetically, and with a high amount of genic variation within individuals. Other forms of monophagy may evolve in species that are essentially monomorphic but with various mechanisms (physiological, developmental, behavioral) of phenotypic flexibility at the individual level. Although the environment is essentially coarse-grained for larvae since most are sedentary and polymorphism is an optimal adaptive strategy, the oviposition strategy of the adult must also be considered and some situations (i.e. forest canopy) have resources (host plants) distributed in a fine-grained fashion. Other forms of limited polyphagy may result from monomorphic genetic systems in which there is considerable phenotypic flexibility.     

Resource-based habitat definition, niche overlap and conservation of two sympatric glacial relict butterflies

The precise knowledge of ecological resources and conditions required by species threatened by rapidly changing environmental conditions is of prime importance for conservation biology. Transferability of this knowledge between species with similar ecological requirements is often assumed, but rarely tested. This is especially the case for glacial relict populations confined to climate‐habitat traps from where they cannot move to rejoin areas with suitable environmental conditions. Using two glacial relict butterflies as model organisms, we first quantitatively define larval and adult resource‐based habitat use of each species. Secondly, we test the transferability of ecological profiles (both habitat and ecological niche) between these two species that share both the same biotope and the same host plant. Our results show that both species have markedly different ecological requirements relating to differences in life history and behavioural traits (i.e. egg‐laying strategies and mate‐locating behaviour). Although the two species share many ecological features, they use different functional habitats within our study site. The high degree of interspecific niche overlap should indicate a high interspecific competition. However, we argue that their co‐existence can be explained by the non‐limiting abundance of some resources (e.g. host plants), by the partial separation in time of adult flight periods and by the territorial behaviour of one of the species. We discuss the following general messages: (1) functional habitat of a (threatened) species should be defined in a spatial context corresponding to individual station keeping, and (2) quick diagnosis based on similar ecological requirements may be misleading for the design of reliable conservation and restoration strategies. Detailed mechanistic and quantitative ecological understanding of resource‐use and environmental tolerances across an organism's life cycle is essential for effective conservation in changing environments, like for glacial relict species.     

Relative contributions of local and regional factors to species richness and total density of butterflies and moths in semi-natural grasslands

Metapopulation theory predicts that species richness and total population density of habitat specialists increase with increasing area and regional connectivity of the habitat. To test these predictions, we examined the relative contributions of habitat patch area, connectivity of the regional habitat network and local habitat quality to species richness and total density of butterflies and day-active moths inhabiting semi-natural grasslands. We studied butterflies and moths in 48 replicate landscapes situated in southwest Finland, including a focal patch and the surrounding network of other semi-natural grasslands within a radius of 1.5 km from the focal patch. By applying the method of hierarchical partitioning, which can distinguish between independent and joint contributions of individual explanatory variables, we observed that variables of the local habitat quality (e.g. mean vegetation height and nectar plant abundance) generally showed the highest independent effect on species richness and total density of butterflies and moths. Habitat area did not show a significant independent contribution to species richness and total density of butterflies and moths. The effect of habitat connectivity was observed only for total density of the declining butterflies and moths. These observations indicate that the local habitat quality is of foremost importance in explaining variation in species richness and total density of butterflies and moths. In addition, declining butterflies and moths have larger populations in well-connected networks of semi-natural grasslands. Our results suggest that, while it is crucial to maintain high-quality habitats by management, with limited resources it would be appropriate to concentrate grassland management and restoration to areas with well-connected grassland networks in which the declining species currently have their strongest populations. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Dispersal in the Glanville fritillary butterfly in fragmented versus continuous landscapes: comparison between three methods

1. Habitat fragmentation may lead to natural selection on dispersal rate and other life‐history traits. Both theoretical analyses and empirical studies suggest that habitat fragmentation may select either for increased or decreased dispersal depending on the traits of the species and the characteristics of the landscape. 2. Dispersal and movement rates in Glanville fritillary butterflies (Melitaea cinxia) originating from a continuous landscape in China and from a highly fragmented landscape in Finland were compared using three different methods. 3. The methods included replicated mark‐release‐recapture (MRR) experiments conducted in the natural environments in China and Finland, tracking with harmonic radar of captive‐reared but free‐flying butterflies in a common environment in the field, and replicated common garden experiments in a large outdoor population cage. 4. The results were largely consistent, showing that butterflies from the more continuous landscape in China had a lower movement rate than butterflies originating from the fragmented landscape in Finland. Butterflies originating from newly‐established populations in Finland moved significantly longer distances than butterflies originating from old populations in Finland or from China, demonstrating significant intra‐specific variation in dispersal rate in Finland. These results are consistent with model predictions for the Glanville fritillary. 5. The tracking experiment revealed a result that would have been impossible to obtain with MRR experiments: movement rate was influenced by a significant interaction between population origin (China vs. Finland) and ambient air temperature.     

Exotic grass invasion impacts fitness of an endangered prairie butterfly, <Emphasis Type="Italic">Icaricia icarioides fenderi</Emphasis>

Fender’s blue butterfly is an endangered species restricted to fragmented, grassland remnants that are becoming increasingly dominated by tall, invasive grasses in western Oregon, USA. I performed a removal experiment to assess the impacts of structural degradation accompanying the invasion of Arrhenatherum elatius, tall oat grass, on butterfly fitness and fitness related behaviors. Clipping of A. elatius to native grass sward height resulted in 2.5–5 times as many eggs laid per leaf of host plant. Both male and female butterflies basked more frequently in areas removed of A. elatius inflorescences and upon encountering the treatment edge butterflies had a high rate of return into a large area removed of the grass inflorescences. Although butterfly behavior appeared to be affected by the change in sward height on the treatment edge, there was no evidence for the edge causing a disproportionate egg load. Invasion and dominance by A. elatius appeared to diminish host plant apparency which may result in overloading of eggs on conspicuous host plants, increased incidence of emigration, and a decrease in the likelihood of colonization because female butterflies appeared indifferent to larval resources beneath A. elatius inflorescences. Dominance of natural shortgrass prairies by tall stature grasses like A. elatius may be an insidious form of habitat degradation for grassland Lepidoptera worldwide, but it may go largely unnoticed because larval and adult resources can persist under the unnaturally tall grass canopy.     

Resource use of specialist butterflies in agricultural landscapes: conservation lessons from the butterfly Phengaris (Maculinea) nausithous

Most of the European grassland butterfly species are dependent on species rich grasslands shaped by low intensity farming. Conservation of these specialist species in agricultural landscapes relies on knowledge of their essential resources and the spatial distribution of these resources. In The Netherlands, the dusky large blue Phengaris (Maculinea) nausithous butterflies were extinct until their reintroduction in 1990. In addition, a spontaneous recolonization of road verges in an agricultural landscape occurred in 2001 in the southern part of The Netherlands. We analyzed the use of the essential resources, both host plants and host ants, of the latter population during the summers of 2003 and 2005. First we tested whether the distribution of the butterflies during several years could be explained by both the presence of host plants as well as host ants, as we expected that the resource that limits the distribution of this species can differ between locations and over time. We found that oviposition site selection was related to the most abundant resource. While in 2003, site selection was best explained by the presence of the host ant Myrmica scabrinodis, in 2005 it was more strongly related to flowerhead availability of the host plant. We secondly compared the net displacement of individuals between the road verge population and the reintroduced population in the Moerputten meadows, since we expected that movement of individuals depends on the structure of their habitat. On the road verges, butterflies moved significantly shorter distances than on meadows, which limits the butterflies in finding their essential resources. Finally we analyzed the availability of the two essential resources in the surroundings of the road verge population. Given the short net displacement distances and the adverse landscape features for long-distance dispersal, this landscape analysis suggests that the Phengaris population at the Posterholt site is trapped on the recently recolonized road verges. These results highlight the importance of assessing the availability of essential resources across different years and locations relative to the movement of the butterflies, and the necessity to careful manage these resources for the conservation of specialist species in agricultural landscapes, such as this butterfly species.     

Conserving Europe’s most endangered butterfly: the Macedonian Grayling (Pseudochazara cingovskii)

The Macedonian Grayling is listed as critically endangered in the recent IUCN Red List of European butterflies because of its extreme rarity and habitat loss due to quarrying. This categorisation was, however, based on rather limited knowledge on its actual distribution, population size and habitat requirements. In 2012, we conducted field surveys to acquire more information. We found the species at six new sites extending its known range of suitable habitat to just under 10 km². The daily population size was estimated using capture-mark-recapture method in the most densely populated part of the Pletvar pass site at more than 650 individuals. Adults proved to be extremely sedentary, not moving far even within the continuous habitat on the same slope. Oviposition was observed on dry plant material and in a rock crevice close to the potential larval host plant Festuca sp. Quarrying is confirmed to be the main threat to the habitat of the Macedonian Grayling with five out of seven populated sites containing active marble quarries. Due to the enlargement of the known area of occupancy, its threat status would now be estimated at endangered. Despite the restricted knowledge about its distribution and trends in the population size, the IUCN criteria proved to be applicable to determine the threat status of a rare and localized butterfly such as Pseudochazara cingovskii. Its original assessment of being called the most threatened butterfly in Europe resulted in immediate research project and subsequent actions that will undoubtedly help to conserve it in the future.     

Habitat complementarity and butterfly traits are essential considerations when mitigating the effects of exotic plantation forestry

Habitat loss threatens insect diversity globally. However, complementary vegetation types in remaining habitat increases opportunities for species survival. We assess the extent to which indigenous forest patches moderate the impact of exotic commercial afforestation on grassland butterflies. Butterflies were sampled in grassland along uncorrelated gradients of landscape-scale indigenous forest and plantation cover, while controlling for variation in local vegetation composition. We separately assessed responses by butterfly groups differing in habitat preference, larval diet, and mobility. There was no effect of landscape- or local-scale variables on species richness, but there was a strong interactive effect of forest and plantation cover on butterfly assemblage structure. The effect varied according to species traits. When forest cover was high, assemblages did not differ at different levels of plantation cover. However, plantation cover significantly influenced assemblage structure when forest cover was low. Grassland with limited forest cover in the protected area supported unique assemblages with high frequency of less mobile, specialized species with herbaceous larval host plants, whereas grassland with low forest cover near plantations had a prevalence of mobile, generalist species. A positive association between forest cover and butterflies with woody larval host plants suggests that indigenous forest patches improved the suitability of fragmented grassland for a subset of butterflies, emphasising the value of natural heterogeneity in transformed areas. However, certain butterfly traits associated with large, open grassland were under-represented in grassland between plantations, underscoring the importance of open areas in the broader landscape to conserve the full diversity of species.

     

Butterfly community structure in fragmented habitats

We analysed effects of habitat fragmentation on the diversity, abundance, and life history traits of butterflies on 33 calcareous grasslands. Diversity of butterflies was positively correlated with habitat area (as was plant diversity), but not with habitat isolation. In contrast to expectations, butterfly densities of polyphagous and oligophagous species declined with habitat area whereas densities of monophagous species increased. The z -values, i.e. the slope of species–area relationships, increased with food plant specialization, from 0.07 in polyphagous, 0.11 in oligophagous, 0.16 in strongly oligophagous to 0.22 in monophagous species, and were 0.14 in plant species. Significant z -values were not only found for total species richness, based on a sample size adjusted to fragment area ( z  = 0.12), but also for the local density of butterfly species richness, based on equal sample size across all habitat fragments ( z  = 0.06). To our knowledge, this is the first study to show differential responses of monophagous, oligophagous and polyphagous species to area with respect to species richness and population density.     

Effects of local and landscape factors on the abundance of an endangered multivoltine butterfly at riverbanks

Plebejus argyrognomon is one of the grassland‐dwelling butterflies undergoing rapid decline in recent decades. Grassland habitats for butterflies are generally threatened by fragmentation and invasive species, hence are among the most vulnerable ecosystems. We studied the seasonal abundance of P. argyrognomon at habitat patches along the banks of the Kinugawa River in eastern Japan, to identify environmental factors suitable for population persistence of this species, including habitat patch connectivity. Results showed that the patch's host plant cover had a positive effect on abundance in all three seasons, while the shading of the host plants by surrounding non‐host plants and nearby forested area showed negative effects. Additionally, habitat patch connectivity and nectar richness could be considered as positive factors in autumn and summer, respectively. Analysis of habitat connectivity also showed that the Kinugawa River did not appear to act as a dispersal barrier for P. argyrognomon. Our findings emphasize the importance of understanding environmental factors that may vary among seasons, and such understanding could contribute to habitat management of multivoltine butterflies in fragmented landscapes.     

Flight patterns of butterfly species in woodlands

Summary The flight patterns of twenty species of butterflies present in two coniferous woods and one coppiced wood in eastern England were recorded from April to September 1979. The most mobile species were those characteristic of disturbed habitats, with spatially segregated larval and adult habitats, and those butterflies with early successional larval host plants. The least mobile species were those of permanent habitats and those with ubiquitous larval host plants. Flights of poorly vagile species, but not vagile species, were restricted in both coniferous and coppiced woodland, but were shorter in the latter due to the presence of vegetational barriers to flight. Vagile species remained in coppiced areas longer than in areas of coniferous woodland, flights being influenced by the location of larval and adult food resources.     

An ecological classification of Central European macromoths: habitat associations and conservation status returned from life history attributes

To be used as a predictive conservation tool, classification of animal habitats should rely on actual resource requirements of individual species. Shreeve et al. (J Insect Conserv 5:145–161, 2001) produced a resource-based habitat classification for British butterflies, obtaining habitat association groups, whose constituent species differed in their distribution extent, distribution change and vulnerability in Britain. To test the utility of this approach for a group with a less-known biology, we produced a resource-based classification of habitats of Central European macromoths. We worked with macrolepidopteran moth families, except for the megadiverse Geometridae and Noctuidae. We produced a matrix of 178 life history attributes describing resource use by 164 species, subjected the matrix to ordination analysis, and compared the resulting moths groupings with external ecological information. Five habitat association groups were distinguished: I—close canopy moths, II—open canopy moths, III—grasslands moths, IV—herb-feeding hawk moths, and V—lichen feeders. The classification sustained deleting attributes related to host plants taxonomy. Groups I–III sustained control for taxonomic positions of the moths, whereas IV and V did not. Members of the groups differed in the representation of externally obtained habitat associations, biogeography elements, threat status, and range size. Endangered species were over-represented in groups II and III and underrepresented in group I, in agreement with recent land cover changes across the continent. Species resources can be used to reconstruct their habitat needs, and it is possible to scale up from life histories through habitat use to range structures.     

The ecology of Myrmica ants in relation to the conservation of Maculinea butterflies

Maculinea butterflies in Europe, and probably most of Asia, are host specific social parasites of various species of Myrmica ants. The latest summary of field data showing the pattern of host specificity by Maculinea is presented. Myrmica ants have been well studied in the laboratory but much less is known about the ecology of their natural populations. While the former is important in understanding the adaptive evolution of Maculinea larval behaviours, the latter is of more practical importance to conservationists charged with the protection of specific populations of Maculinea. The current knowledge of habitat partition, colony growth and colony reproduction within communities of Myrmica ants is summarized in relation to the ecology of Maculinea species. Concepts used in current population simulation models are explained. A key concept is the idea that community structure (both number of species and size and abundance of nests) is controlled by the quantity and quality of suitable nest sites. Some advice is given to conservationists who might need to manipulate Myrmica ant populations in order to maintain a robust population of a Maculinea species. © Rapid Science Ltd. 1998     

Diapause termination in two species of tropical butterfly, Euploea core (Cramer) and Euploea sylvester (Fabricius) (Lepidoptera: Nymphalidae)

Abstract This study examined the factors used as cues for diapause termination by two Euploea species. Euploea core and E. sylvester were collected from two overwintering sites at Chillagoe, Queensland. Under tropical wet-season conditions, more butterflies terminated diapause (approximately 60%) than those kept under dry-season conditions (approximately 40%). However, 100% diapause termination occurred only when butterflies were kept under wet-season conditions and were fed with honey. For reproductive success, Euploea species need to terminate diapause rapidly to synchronise oviposition with fresh, rapid growth of their larval host plants, which often occurs after rain. The presence of rainfall, increased temperature and long days alone is not a fail-safe set of cues for this event. Our results suggest that food (as nectar), in conjunction with these combined environmental factors, provide Euploea species with a reliable signal that larval host resources are available for oviposition.