Unpalatable Butterflies Research Articles

Evaluating an Alleged Mimic of the Monarch Butterfly: Neophasia (Lepidoptera: Pieridae) Butterflies are Palatable to Avian Predators.

Some taxa have adopted the strategy of mimicry to protect themselves from predation. Butterflies are some of the best representatives used to study mimicry, with the monarch butterfly, Danaus plexippus (Lepidoptera: Nymphalidae) a well-known model. We are the first to empirically investigate a proposed mimic of the monarch butterfly: Neophasia terlooii, the Mexican pine white butterfly (Lepidoptera: Pieridae). We used captive birds to assess the palatability of N. terlooii and its sister species, N. menapia, to determine the mimicry category that would best fit this system. The birds readily consumed both species of Neophasia and a palatable control species but refused to eat unpalatable butterflies such as D. plexippus and Heliconius charithonia (Lepidoptera: Nymphalidae). Given some evidence for mild unpalatability of Neophasia, we discuss the results considering modifications to classic mimicry theory, i.e., a palatability-based continuum between Batesian and Müllerian mimicry, with a quasi-Batesian intermediate. Understanding the ecology of Neophasia in light of contemporary and historical sympatry with D. plexippus could shed light on the biogeography of, evolution of, and predation pressure on the monarch butterfly, whose migration event has become a conservation priority.

Subtle variation in size and shape of the whole forewing and the red band among co-mimics revealed by geometric morphometric analysis in Heliconius butterflies.

Heliconius are unpalatable butterflies that exhibit remarkable intra‐ and interspecific variation in wing color pattern, specifically warning coloration. Species that have converged on the same pattern are often clustered in Müllerian mimicry rings. Overall, wing color patterns are nearly identical among co‐mimics. However, fine‐scale differences exist, indicating that factors in addition to natural selection may underlie wing phenotype. Here, we investigate differences in shape and size of the forewing and the red band in the Heliconius postman mimicry ring (H. erato phyllis and the co‐mimics H. besckei, H. melpomene burchelli, and H. melpomene nanna) using a landmark‐based approach. If phenotypic evolution is driven entirely by predation pressure, we expect nonsignificant differences among co‐mimics in terms of wing shape. Also, a reinforcement of wing pattern (i.e., greater similarity) could occur when co‐mimics are in sympatry. We also examined variation in the red forewing band because this trait is critical for both mimicry and sexual communication. Morphometric results revealed significant but small differences among species, particularly in the shape of the forewing of co‐mimics. Although we did not observe greater similarity when co‐mimics were in sympatry, nearly identical patterns provided evidence of convergence for mimicry. In contrast, mimetic pairs could be distinguished based on the shape (but not the size) of the red band, suggesting an “advergence” process. In addition, sexual dimorphism in the red band shape (but not size) was found for all lineages. Thus, we infer that natural selection due to predation by birds might not be the only mechanism responsible for variation in color patterns, and sexual selection could be an important driver of wing phenotypic evolution in this mimicry ring.

Both Palatable and Unpalatable Butterflies Use Bright Colors to Signal Difficulty of Capture to Predators

Birds are able to recognize and learn to avoid attacking unpalatable, chemically defended butterflies after unpleasant experiences with them. It has also been suggested that birds learn to avoid prey that are efficient at escaping. This, however, remains poorly documented. Here, we argue that butterflies may utilize a variety of escape tactics against insectivorous birds and review evidence that birds avoid attacking butterflies that are hard to catch. We suggest that signaling difficulty of capture to predators is a widespread phenomenon in butterflies, and this ability may not be limited to palatable butterflies. The possibility that both palatable and unpalatable species signal difficulty of capture has not been fully explored, but helps explain the existence of aposematic coloration and escape mimicry in butterflies lacking defensive chemicals. This possibility may also change the role that putative Müllerian and Batesian mimics play in a variety of classical mimicry rings, thus opening new perspectives in the evolution of mimicry in butterflies.

A genetic mechanism for female-limited Batesian mimicry in Papilio butterfly.

In Batesian mimicry, animals avoid predation by resembling distasteful models. In the swallowtail butterfly Papilio polytes, only mimetic-form females resemble the unpalatable butterfly Pachliopta aristolochiae. A recent report showed that a single gene, doublesex (dsx), controls this mimicry; however, the detailed molecular mechanisms remain unclear. Here we determined two whole-genome sequences of P. polytes and a related species, Papilio xuthus, identifying a single ∼130-kb autosomal inversion, including dsx, between mimetic (H-type) and non-mimetic (h-type) chromosomes in P. polytes. This inversion is associated with the mimicry-related locus H, as identified by linkage mapping. Knockdown experiments demonstrated that female-specific dsx isoforms expressed from the inverted H allele (dsx(H)) induce mimetic coloration patterns and simultaneously repress non-mimetic patterns. In contrast, dsx(h) does not alter mimetic patterns. We propose that dsx(H) switches the coloration of predetermined wing patterns and that female-limited polymorphism is tightly maintained by chromosomal inversion.

A model for population dynamics of the mimetic butterfly Papilio polytes in the Sakishima Islands, Japan

We present a mathematical model for population dynamics of the mimetic swallowtail butterfly Papilio polytes in the Sakishima Islands, Japan. The model includes four major variables, that is, population densities of three kinds of butterflies (two female forms f. cyrus, f. polytes and the unpalatable butterfly Pachliopta aristolochiae) and their predator. It is well-known that the non-mimic f. cyrus resembles and attracts the male most, and the mimic f. polytes mimics the model butterfly P. aristolochiae. Based on experimental evidence, we assume that two forms f. cyrus and f. polytes interact under intraspecific competition for resources including the male, and the growth rate of f. cyrus is higher than that of f. polytes. We further assume that both the benefit of mimicry for the mimic f. polytes and the cost for the model are dependent on their relative frequencies, i.e. the motality of the mimic by predation decreases with increase in frequency of the model, while the motality of the model increases as the frequency of the mimic increases. Taking the density-dependent effect through carrying capacity into account, we set up a model system consisting of three ordinary differential equations (ODEs), analyze it mathematically and provide computer simulations that confirm the analytical results. Our results reproduce field records on population dynamics of P. polytes in the Miyako-jima Island. They also explain the positive dependence of the relative abundance (RA) of the mimic on the advantage index (AI) of the mimicry in the Sakishima Islands defined in Section 2.

Phylogeny of Neotropical Castniinae (Lepidoptera: Cossoidea: Castniidae): testing the hypothesis of the mimics as a monophyletic group and implications for the arrangement of the genera

A cladistic analysis of the Neotropical Castniidae is presented using 120 morphological characters, and a taxonomic treatment based on that analysis is also presented. The tribe Gazerini as previously delimited was found to be paraphyletic with respect to the genera Ceretes, Divana, Riechia, Frostetola, and Oiticicastnia. The genera Castnia, Geyeria, and Athis were also found to be non-monophyletic taxa. The mimicry pattern had multiple independent origins in the Neotropical castniids, and at least two lineages, Riechia and Prometheus, are involved in Batesian mimicry rings with unpalatable butterfly models in the tribes Acraeini and Heliconiini (Nymphalidae). We propose for Castniini 13 new synonymies and 27 new combinations. Geyeria strigata (Walker, 1854) is revalidated. The generic placements of Athis superba (Strand, 1912) and Castnia eudesmia Gray, 1838 are questionable, but presently upheld. © 2014 The Linnean Society of London

Molecular basis of wing coloration in a Batesian mimic butterfly, Papilio polytes

Batesian mimicry protects animals from predators through resemblance with distasteful models in shape, color pattern, or behavior. To elucidate the wing coloration mechanisms involved in the mimicry, we investigated chemical composition and gene expression of the pale yellow and red pigments of a swallowtail butterfly, Papilio polytes, whose females mimic the unpalatable butterfly Pachliopta aristolochiae. Using LC/MS, we showed that the pale yellow wing regions in non-mimetic females consist of kynurenine and N-β-alanyldopamine (NBAD). Moreover, qRT-PCR showed that kynurenine/NBAD biosynthetic genes were upregulated in these regions in non-mimetic females. However, these pigments were absent in mimetic females. RNA-sequencing showed that kynurenine/NBAD synthesis and Toll signaling genes were upregulated in the red spots specific to mimetic female wings. These results demonstrated that drastic changes in gene networks in the red and pale yellow regions can switch wing color patterns between non-mimetic and mimetic females of P. polytes.

WING SHAPE VARIATION ASSOCIATED WITH MIMICRY IN BUTTERFLIES

Mimetic resemblance in unpalatable butterflies has been studied by evolutionary biologists for over a century, but has largely focused on the convergence in wing color patterns. In Heliconius numata, discrete color-pattern morphs closely resemble comimics in the distantly related genus Melinaea. We examine the possibility that the shape of the butterfly wing also shows adaptive convergence. First, simple measures of forewing dimensions were taken of individuals in a cross between H. numata morphs, and showed quantitative differences between two of the segregating morphs, f. elegans and f. silvana. Second, landmark-based geometric morphometric and elliptical Fourier outline analyses were used to more fully characterize these shape differences. Extension of these techniques to specimens from natural populations suggested that, although many of the coexisting morphs could not be discriminated by shape, the differences we identified between f. elegans and f. silvana hold in the wild. Interestingly, despite extensive overlap, the shape variation between these two morphs is paralleled in their respective Melinaea comimics. Our study therefore suggests that wing-shape variation is associated with mimetic resemblance, and raises the intriguing possibility that the supergene responsible for controlling the major switch in color pattern between morphs also contributes to wing shape differences in H. numata.

Are Corporal Allometric Measurements Good Predictors of Palatability in Neotropical Butterflies (Lepidoptera)?

Since palatable butterflies are more dependent on evasive flight to escape from predators, they should be more restricted in their flight-related morphology than unpalatable ones. We compared: the ratios between the (1) length of head plus thorax and the length of abdomen (A/B), (2) length of the tip of the head to wing base and the length of the wing base to end of the abdomen (C/D), (3) the variances of A/B and C/D, (4) the proportion between the thoracic and the body weight, and (5) the flight speed between palatable and unpalatable butterflies. A/B and thoracic/body weight were higher for palatable species, indicating higher body symmetry and muscular mass. However, flight speed did not differ. Unexpectedly, the variance of A/B was higher for palatable species while that of C/D did not differ. Therefore, corporal allometric measurements of Neotropical butterflies are good predictors of palatability, though not of flight speed.

Behavioral Batesian Mimicry Involving lntraspecific Polymorphism in the ButterflyPapilio polytes

Batesian mimics gain protection from predation by their similarity to distasteful models. In butterflies, it has been thought that distasteful species and Batesian mimics fly slowly and in a straight line, but few studies have demonstrated their behavioral similarity, and no studies have been conducted on behavioral mimicry Involving Batesian intraspecific polymorphism. Here, we compared the wing stroke among various butterflies: palatable non-mimetic Papilio xuthus, unpalatable Pachliopta aristolochiae, and palatable polymorphic Papilio polytes (cyrus form, non-mimetic females; polytes form, Batesian mimetic females) to clarify whether the wing stroke of unpalatable butterflies is different from that of palatable species, whether that of the non-mimetic females of Pap. polytes is different from the mimetic females, and whether that of the mimetic females resembles that of the model. We found that the minimum positional angle (phi(min)) of Pach. aristolochiae and mimetic females of Pap. polytes was significantly larger than that of Pap. xuthus and non-mimetic females. We did not detect significant differences between that of Pach. aristolochiae and mimetic females of Pap. polytes. These results show that phi(min) differed between the mimicry group and palatable butterflies. In addition, the wingbeat frequency (WBF) of Pach. aristolochiae and mimetic females tended to differ from that of Pap. xuthus and non-mimetic females. This result suggests that there may be convergence of WBF in Batesian mimicry groups, as in the case of Müllerian mimicry groups, and serves as the first evidence of behavioral mimicry in Batesian intraspecific polymorphism.

Batesian Mimicry: Can a Leopard Change Its Spots — and Get Them Back?

Can undefended mimics survive outside the range of their noxious models? Two recent studies on Batesian mimicry suggest they can, but alternative survival strategies and morphologies are then favoured.

Evolution of the wave: aerodynamic and aposematic functions of butterfly wing motion

Many unpalatable butterfly species use coloration to signal their distastefulness to birds, but motion cues may also be crucial to ward off predatory attacks. In previous research, captive passion-vine butterflies Heliconius mimetic in colour pattern were also mimetic in motion. Here, I investigate whether wing motion changes with the flight demands of different behaviours. If birds select for wing motion as a warning signal, aposematic butterflies should maintain wing motion independently of behavioural context. Members of one mimicry group (Heliconius cydno and Heliconius sapho) beat their wings more slowly and their wing strokes were more asymmetric than their sister-species (Heliconius melpomene and Heliconius erato, respectively), which were members of another mimicry group having a quick and steady wing motion. Within mimicry groups, wing beat frequency declined as its role in generating lift also declined in different behavioural contexts. In contrast, asymmetry of the stroke was not associated with wing beat frequency or behavioural context-strong indication that birds process and store the Fourier motion energy of butterfly wings. Although direct evidence that birds respond to subtle differences in butterfly wing motion is lacking, birds appear to generalize a motion pattern as much as they encounter members of a mimicry group in different behavioural contexts.

THE COST OF BAD TASTE

Some butterflies have evolved a special defence against predators –they taste bad. And they want predators to recognize them as bad-tasting, so they're brightly coloured and fly slowly and steadily to show off their colours. Between the colouration and slow flight, predators can spot them easily, so they're easy to catch. But once predators learn to associate bright colours and slow flight with bad taste, they avoid these butterflies. In evolutionary terms, the colouration and flight pattern is an `honest signal':it has both costs and benefits. Unpalatable butterflies pay the cost of being easy to spot but gain the benefit of predators learning to avoid them.It seems that there might be a loophole in this arrangement. If good-tasting butterflies mimic the same bright coloration and flight pattern as bad-tasting ones, then the mimics get the benefits without the costs. For some reason, however, there are very few of these brightly coloured tasty butterflies, called Batesian mimics, and Robert Srygley explores possible reasons why in his recent paper.Srygley wondered whether flight pattern might help explain the lack of Batesian mimics. He had a hunch that the slow steady flight used by both the mimics and the bad-tasting butterflies might take a lot of energy, which would make it less beneficial to bother being a mimic. The quick and erratic way normal palatable butterflies fly might be easier, possibly explaining why so few butterflies have gone down the Batesian route. And as they are so rare, it wasn't clear before he started his study whether they fly erratically, like the good-tasting butterflies they are, or slowly, like the bad-tasting butterflies they mimic.Srygley filmed the flight patterns of three orange tiger-striped unpalatable butterflies, three Batesian mimics modelled on the orange tiger-striped butterflies, and two species of tasty green butterflies closely related to the mimics. Would the Batesian mimics fly slowly like the foul orange tiger-striped butterflies or erratically like the tasty green butterflies? For the first time, he demonstrated that Batesian mimics do fly in the same way as the unpalatable butterflies that they are modelled on: not only did they both have similar wing beat speeds but they also both flew significantly slower than the green palatable butterflies.From these films, he also estimated the power each butterfly uses to fly at ordinary speeds of ∼1 m s–1 using a relatively simple mathematical theory. Because of the flight pattern differences, both the mimics and the distasteful butterflies that they mimic used significantly more power to fly than the tasty green ones. Interestingly, the mimics also used substantially more power than the conspicuous orange tiger-striped butterflies. Thus, it was most costly to be a mimic, least costly to fly in a`normal' fast way and in-between to fly slowly like the bad-tasting conspicuous butterflies.Srygley hypothesized that Batesian mimics try to do too much – they fly slowly like unpleasant tasting butterflies when they aren't threatened but fly erratically like palatable butterflies when they're pursued. As a result,they aren't very good at either and don't get much benefit from their mimicry,which may be why there aren't many Batesian mimics.

Are European White Butterflies Aposematic?

It has been suggested that the white coloration of Pieridae butterflies is a warning signal and therefore all white Pieridae could profit from a mimetic resemblance. We tested whether green-veined white (Pieris napi) and orange-tip (Anthocharis cardamines) butterflies benefit from white coloration. We compared their relative acceptability to wild, adult pied flycatchers (Ficedula hypoleuca) by offering live A. cardamines and P. napi together with two non-aposematic butterflies on the tray attached to birds' nesting boxes. Experienced predators equally attacked white and non-white butterflies, and the order of attack among the Pieridae was random. If anything, there was a slight indication that the female A. cardamines was the least favoured prey. Since birds did not avoid white coloration, we compared the palatability of these two species against known palatable and unpalatable butterflies by presenting them to great tits (Parus major). Pieris brassicae, which has been earlier described as unpalatable, was also included in the palatability test. However, there were no significant differences in the palatability of the butterflies to birds, and even P. brassicae was apparently palatable to the great tits. Our results do not unambiguously support the hypothesis that the white coloration of Pieridae would signal unpalatability. Nevertheless, in our last experiment, pied flycatchers often rejected or left untouched free flying P. napi and A. cardamines. This suggests that other features in a more natural situation, such as the agile flight pattern or odours might still make them unprofitable to birds.

Butterfly visual characteristics and ontogeny of responses to butterflies by a specialized tropical bird

The responses of two adult and three hand-reared, naive young rufous-tailed jacamars (Galbula ruficauda) to local butterflies were studied in feeding experiments. Four behavioural characteristics distinguish jacamars from other less specialized avian predators: (1) Exposed to butterflies for the first time, naive young jacamars would attack butterflies without showing signs of inhibition. Unacceptable butterflies, once captured, were taste-rejected quickly, and most survived the sampling. The few presumably unacceptable butterflies consumed by the birds were not observed to cause vomiting. (2) After gaining some familiarity with butterflies, young birds, like the adults, developed a reluctance to attack. They visually rejected certain classes of butterflies, often failing to attack them during an entire four-hour feeding trial. However, occasional attacks were made on butterflies in these ‘rejected’ classes. When this did occur, the insects proved to be actually easier to catch than those that were more often attacked. Once captured, however, the majority of these butterflies were taste-rejected. (3) For a given butterfly species, most individuals were either consumed or rejected. Thus, each species could be clearly classified as either acceptable or unacceptable to the jacamars. This consistency in jacamar responses resulted in a bimodal acceptability distribution of sympatric butterflies. (4) Young jacamars were capable of rapid associative learning and their responses were closely associated with butterfly visual characteristics in which colour pattern, flight behaviour, and morphology were also closely correlated. Thus, a single butterfly morphological parameter termed body shape (body length/thoracic diameter ratio) can adequately predict the feeding responses of jacamars. Visually detectable traits associated with butterflies possessing chemical defences may represent a balance between the need to signal unambiguously to specialized and/or experienced predators and the need to escape attacks by generalized and/or opportunistic predators. Since the proportion of specialized predators is higher in the tropical rainforest than in other habitat types, we expect greater divergence of morphological and behavioural characteristics between palatable and unpalatable butterflies in rainforest habitats.

Butterfly visual characteristics and ontogeny of responses to butterflies by a specialized tropical bird

The responses of two adult and three hand-reared, naive young rufous-tailed jacamars (Galbula ruficauda) to local butterflies were studied in feeding experiments. Four behavioural characteristics distinguish jacamars from other less specialized avian predators: (1) Exposed to butterflies for the first time, naive young jacamars would attack butterflies without showing signs of inhibition. Unacceptable butterflies, once captured, were taste-rejected quickly, and most survived the sampling. The few presumably unacceptable butterflies consumed by the birds were not observed to cause vomiting. (2) After gaining some familiarity with butterflies, young birds, like the adults, developed a reluctance to attack. They visually rejected certain classes of butterflies, often failing to attack them during an entire four-hour feeding trial. However, occasional attacks were made on butterflies in these ‘rejected’ classes. When this did occur, the insects proved to be actually easier to catch than those that were more often attacked. Once captured, however, the majority of these butterflies were taste-rejected. (3) For a given butterfly species, most individuals were either consumed or rejected. Thus, each species could be clearly classified as either acceptable or unacceptable to the jacamars. This consistency in jacamar responses resulted in a bimodal acceptability distribution of sympatric butterflies. (4) Young jacamars were capable of rapid associative learning and their responses were closely associated with butterfly visual characteristics in which colour pattern, flight behaviour, and morphology were also closely correlated. Thus, a single butterfly morphological parameter termed body shape (body length/thoracic diameter ratio) can adequately predict the feeding responses of jacamars. Visually detectable traits associated with butterflies possessing chemical defences may represent a balance between the need to signal unambiguously to specialized and/or experienced predators and the need to escape attacks by generalized and/or opportunistic predators. Since the proportion of specialized predators is higher in the tropical rainforest than in other habitat types, we expect greater divergence of morphological and behavioural characteristics between palatable and unpalatable butterflies in rainforest habitats.

Locomotor mimicry in butterflies? A critical review of the evidence

The hypothesis of locomotor mimicry in butterflies presented by Srygley (Phil. Trans. R. Soc. Lond.B 343, 145—155 (1994)) is criticized as unparsimonious, from two perspectives. First, the existence of mimicry between palatable but unprofitable prey is disputed on theoretical and empirical grounds. The lack of a strong predator aversion stimulus seriously undermines the unprofitable prey scenario, and supposed cases of mimicry of unprofitable models are explicable by traditional mimetic modes. Second, correlations of phenotypic characters used to support alternative adaptive peaks for palatable and unpalatable butterflies are criticized for failing to account for phylogenetic relationships. Virtually all of the relevant variation in flight-related morphology is shown to be due to differences between clades, rather than mimicry groups. An alternative hypothesis emphasizing phylogenetic constraint in the evolution of morphological characters associated with predator avoidance is proposed. The ground rule — or perhapsdoctrinewould be a better term — is that adaptation is a special and onerous concept that should be used only where it is really necessary. When it must be recognized, it should be attributed to no higher a level of organization than is demanded by the evidence. In explaining adaptation, one should assume the adequacy of the simplest form of natural selection, that of alternate alleles in Mendelian populations, unless the evidence clearly shows that this theory does not suffice. G. C. Williams (1966, pp. 4—5).

Locomotor mimicry in butterflies? The associations of positions of centres of mass among groups of mimetic, unprofitable prey

With detailed measurements of flight-related morphological parameters of 18 species within the tribe Heliconiini and 10 of their non-heliconiine comimics, I found that morphological parameters relevant to flight biomechanics are associated with three escape tactics of these Neotropical butterflies: evasive flight, distastefulness, and mimicry. Two distinct character suites, one pertaining to the position of centre of body mass and another pertaining to wing shape, were identified using principal-components analysis. A third component correlated most highly with the position of centre of wing mass. Mimicry groups were best discriminated by the positions of centres of body and wing mass, suggesting that these features converged within mimicry groups. Centres of mass were positioned nearer to the wing base in mimicry groups composed of more palatable species, presumably decreasing the radial moments of inertia of the body and wings and increasing flight speed and turning performance. Predation has selected for body morphology that increases flight speed and manoeuvrability in palatable butterflies, whereas the morphology of distasteful species compromises flight performance. Convergent selection may reduce morphological differences of species within mimicry groups arising from distantly related lineages, and hence it may have enhanced the morphological diversification of palatable and unpalatable butterflies within lineages that have more recently evolved distastefulness.

Polymorphic Müllerian mimicry in a group of African butterflies: a re‐assessment of the relationship between Danaus chrysippus, Acraea encedon and Acraea encedana (Lepidoptera: Nymphalidae)

Müllerian mimicry, in which there is convergence in coloration between unrelated unpalatable species, should lead to uniformity in appearance, not polymorphism, and so the occurrence in tropical Africa of unrelated species of unpalatable butterflies with corresponding polymorphic colour forms suggested a problem of special evolutionary interest. Field work in Uganda and Sierra Leone in 1964 72 demonstrated a statistical association between the occurrence and relative frequencies of polymorphic forms in Danaus chrysippus (Danainae) and Acraea encedon (Acraeinae) which was deemed as confirmation of a Müllerian relationship between them. There were, however, certain anomalies which at the time remained unresolved. Later, in 1976, it was discovered that what had been called A. encedon is in reality two sibling species. A. encedon and a new one, named as A. encedana. The two differ in the structure of both male and female genitalia and in the coloration and the food‐plants of the larvae. The recognition of the additional species has enabled a re‐assessment of the polymorphie Müllerian association with D. chrysippus. It emerges that, although there is a close qualitative and quantitative reciprocal mimetic relationship between A. encedana and D. chrysippus, the relationship between A. encedon and D. chrysippus is much weaker, and in places non‐exitent. The possible origin of the mimetic polymorphism is discussed in terms of hybridization of previously allopatric and monomorphic populations which have met as a consequence of recent expansions of geographical range in all three species resulting from forest clearance and the spread of savanna‐like conditions in previously forested areas.

Thermoregulation in Unpalatable Danaine Butterflies

Thoracic temperatures of two species of unpalatable danaine butterflies in Papua New Guinea were high, exceeding ambient temperature on average by 5-5?C. Males and females of both species flew under conditions of intense solar irradiance, and in most cases showed significant regulation of thoracic temperature. Thoracic temperature excess was not, however, positively correlated with solar irradiance, body mass, or wing loading. In general, equilibrium temperature of a flying butterfly is influenced by choice of microhabitat, flight metabolism, and convective cooling. Interactions between these factors can be complex, and may alternatively result in thoracic temperatures close to ambient (as reported previously for unpalatable neotropical butterflies), or in a high thoracic excess, as exemplified by the danaine butterflies considered here. Association between palatability and thermal biology in butterflies thus has a variety of possible outcomes. Key-words: Danaine butterfly, palatability, Papua New Guinea, thermoregulation