Seasonal phenotypic plasticity of wing melanisation in the cabbage white butterfly, Pieris rapae L. (Lepidoptera: Pieridae)

Abstract.  1. Effective thermoregulation is crucial for the fitness of small flying insects. Phenotypic plasticity of the ventral hindwing of pierid butterflies is widely recognised as adaptive for effective thermoregulation. Butterflies eclosing in cooler environments have more heavily melanised wings that absorb solar radiation, thus allowing flight under these cool conditions.
2. Many pierids also exhibit phenotypic plasticity of dorsal forewing melanisation but in this case, cooler environments reduce melanisation. It has been hypothesised that this plasticity is also adaptive because it increases solar reflection from the wing surfaces onto the body in certain basking postures.
3. The degree of seasonal variation in ventral hindwing and dorsal forewing melanisation of wild-caught Pieris rapae was quantified to determine if it shows patterns of plasticity similar to that documented for other Pieris species.
4. Male wing melanisation on both wing surfaces shows the characteristic seasonal, adaptive plasticity. However, only some dorsal forewing pattern elements of females conformed to the predictions of the hypothesis of adaptive dorsal forewing melanisation. Sexual dimorphism of wing pattern plasticity may result from, and/or affect, sexual dimorphism of behaviour and physiology of these butterflies.     

Thermal characterization of butterfly wings—1. Absorption in relation to different color, surface structure and basking type

1. 1. Spectral integral reflectance, transmittance and the resulting absorption of intact and descaled butterfly wings of the black-winged Pachliopta aristolochiae (Papilionidae), the white-winged Pieris brassicae (Pieridae), and the yellow-winged Gonepteryx rhamni (Pieridae) were determined between 350 and 800 nm.

2. 2. Whereas in the black forewing of the dorsal basking Pachliopta almost all incident light is absorbed nearly independent of the wavelength and thus converted into heat, the white forewing of the body basking Pieris absorbs less than 20% in the visible range of the spectrum.

3. 3. The yellow hindwing of the lateral basking Gonepteryx absorbs to a higher degree than the Pierid wing, but—due to the sparsely arranged scales—transmittance is clearly increased (40–50% between 525 and 800 nm).

4. 4. The varying thermal characteristics of the different wings with reference to the color and arrangement of the scales and the different basking strategies of the butterflies are discussed.

Warning coloration can be disruptive: aposematic marginal wing patterning in the wood tiger moth

Warning (aposematic) and cryptic colorations appear to be mutually incompatible because the primary function of the former is to increase detectability, whereas the function of the latter is to decrease it. Disruptive coloration is a type of crypsis in which the color pattern breaks up the outline of the prey, thus hindering its detection. This delusion can work even when the prey's pattern elements are highly contrasting; thus, it is possible for an animal's coloration to combine both warning and disruptive functions. The coloration of the wood tiger moth (Parasemia plantaginis) is such that the moth is conspicuous when it rests on vegetation, but when it feigns death and drops to the grass‐ and litter‐covered ground, it is hard to detect. This death‐feigning behavior therefore immediately switches the function of its coloration from signaling to camouflage. We experimentally tested whether the forewing patterning of wood tiger moths could function as disruptive coloration against certain backgrounds. Using actual forewing patterns of wood tiger moths, we crafted artificial paper moths and placed them on a background image resembling a natural litter and grass background. We manipulated the disruptiveness of the wing pattern so that all (marginal pattern) or none (nonmarginal pattern) of the markings extended to the edge of the wing. Paper moths, each with a hidden palatable food item, were offered to great tits (Parus major) in a large aviary where the birds could search for and attack the “moths” according to their detectability. The results showed that prey items with the disruptive marginal pattern were attacked less often than prey without it. However, the disruptive function was apparent only when the prey was brighter than the background. These results suggest that warning coloration and disruptive coloration can work in concert and that the moth, by feigning death, can switch the function of its coloration from warning to disruptive.     

Fine nanostructural variation in the wing pattern of a moth <Emphasis Type="Italic">Chiasmia eleonora</Emphasis> Cramer (1780)

Butterflies and moths possess diverse patterns on their wings. Butterflies employ miscellaneous colour in the wings whereas moths use a combination of dull colours like white, grey, brown and black for the patterning of their wings. The exception is some of the toxic diurnal moths which possess bright wing colouration. Moths possess an obscure pattern in the dorsal part of the wings which may be a line, zigzag or swirl. Such patterns help in camouflage during resting period. Thus, the dorsal wing pattern of the moth is used for both intra- as well as inter-specific signal communication. Chiasmia eleonora is a nocturnal moth of greyish black colouration. The dorsal hindwing possesses yellow and black colour patches. A white-coloured oblique line crosses both left and right fore- and hindwings to form a V-shaped pattern across the dorsal wing. This V-shaped pattern possesses a UV signal. Closer to the body, the colour appears darker, which fades towards the margin. The fine nanostructural variation is observed throughout the wings. This study elucidates the wing pattern of the geometrid moth C. eleonora using high-resolution microscopy techniques that has not been described in previous studies.     

Colour pattern homology and evolution in Vanessa butterflies (Nymphalidae: Nymphalini): eyespot characters

Ocelli are serially repeated colour patterns on the wings of many butterflies. Eyespots are elaborate ocelli that function in predator avoidance and deterrence as well as in mate choice. A phylogenetic approach was used to study ocelli and eyespot evolution in Vanessa butterflies, a genus exhibiting diverse phenotypes among these serial homologs. Forty‐four morphological characters based on eyespot number, arrangement, shape and the number of elements in each eyespot were defined and scored. Ocelli from eight wing cells on the dorsal and ventral surfaces of the forewing and hindwing were evaluated. The evolution of these characters was traced over a phylogeny of Vanessa based on 7750 DNA base pairs from 10 genes. Our reconstruction predicts that the ancestral Vanessa had 5 serially arranged ocelli on all four wing surfaces. The ancestral state on the dorsal forewing and ventral hindwing was ocelli arranged in two heterogeneous groups. On the dorsal hindwing, the ancestral state was either homogenous or ocelli arranged in two heterogeneous groups. On the ventral forewing, we determined that the ancestral state was organized into three heterogeneous groups. In Vanessa, almost all ocelli are individuated and capable of independent evolution relative to other colour patterns except for the ocelli in cells ?1 and 0 on the dorsal and ventral forewings, which appear to be constrained to evolve in parallel. The genus Vanessa is a good model system for the study of serial homology and the interaction of selective forces with developmental architecture to produce diversity in butterfly colour patterns.     

Morphology of hindwing veins in the shield bug Graphosoma italicum (Heteroptera: Pentatomidae)

Light, fluorescence, and electron microscopy were applied to cross sections and -breakage and whole-mount preparations of the anterior hindwing vein of the shield bug Graphosoma italicum. These analyses were complemented by investigations of the basal part of the forewing Corium and Clavus. The integration of structural, histological, and fluorescence data revealed a complex arrangement of both rigid and elastic structures in the wall of wing veins and provided insights into the constitution of transition zones between rigid and elastic regions. Beneath the exocuticular layers, which are continuous with the dorsal and ventral cuticle of the wing membrane, the lumen of the veins is encompassed by a mesocuticular layer, an internal circular exocuticular layer, and an internal longitudinal endocuticular layer. Separate parallel lumina within the anterior longitudinal vein of the hindwing, arranged side-by-side rostro-caudally, suggest that several veins have fused in the phylogenetic context of vein reduction in the pentatomid hindwing. Gradual structural transition zones and resilin enrichment between sclerotized layers of the vein wall and along the edges of the claval furrow are interpreted as mechanical adaptations to enhance the reliability and durability of the mechanically stressed wing veins.     

Wing colors of Chrysozephyrus butterflies (Lepidoptera; Lycaenidae): ultraviolet reflection by males

Wing colors of the four species of Chrysozephyrus butterflies were analyzed by a spectrophotometer. As the dorsal wing surface of males showed a strong reflectance when the specimen was tilted, measurements were made by the tilting method. The dorsal wing surface of males which appears green to the human eye reflected UV (315-350 nm) as well as green light (530-550 nm). The reflectance rate of UV to visible green light varied among species with a higher rate for C. hisamatsusanus and C. ataxus, and a lower rate for C. smaragdinus and C. brillantinus. The peak wavelength and the peak height did not shift when the specimen was exposed to direct sunlight at least for 16 hr. Artificial removal of scales by scratching the wing surface decreased reflectance. Blue marks on the forewings of C. brillantinus, C. hisamatsusanus and C. ataxus females reflected UV to visible light of short wavelength, and orange marks on the dorsal surface of the forewing and the ventral surface of the hindwing of C. samaragdinus females showed a higher reflectance at longer wavelengths.     

Sexual Size Dimorphism in the Color Pattern Elements of Two Mimetic Heliconius Butterflies

Sexual dichromatism and sexual dimorphism of body size are reasonably well studied in butterflies. Sexual size dimorphism of color pattern elements, however, is much less explored. The object of this study is Heliconius, a genus of butterflies well known for the coevolution between mate color preferences and mimicry. Given the sexual role of wing coloration, we investigated the existence of sexual size dimorphism in the wing color elements of a mimetic pair—Heliconius erato phyllis Fabricius and Heliconius besckei Ménétriés—and analyzed the allometric patterns of these traits. Correlation between size of elements in the dorsal and ventral wing surfaces were also estimated. In both species, three out of four elements were larger in males, but the non-dimorphic element was not the same. With regard to the allometric patterns, our most important finding was that smaller males of one species have proportionally larger yellow bars. This is the first study specifically concerning quantitative sexual dimorphism in the coloration of this well-known genus of butterflies and it opens new prospects to investigate sex-related natural selection and sexual selection of color pattern elements.     

Female preferences for aposematic signal components in a polymorphic poison frog

Aposematic signals may be subject to conflicting selective pressures from predators and conspecifics. We studied female preferences for different components of aposematic coloration in the polymorphic poison frog Oophaga pumilio across several phenotypically distinct populations. This frog shows striking diversity in color and pattern between geographically isolated populations in western Panama. Results indicate that male dorsal color is the most important determiner of female preferences. We did not find consistent evidence for effects of other signal components, such as spotting pattern or ventral color. Females in two populations showed assortative preferences mediated by male dorsal coloration. In a third population we found incomplete color-assortative preference behavior, with females exhibiting strong discrimination toward one novel color but not another. These results hint at a possible interaction between sexual and natural selection: female tolerance of unfamiliar coloration patterns could facilitate the establishment of novel phenotypes that are favored by other selective pressures (e.g., predator biases). Furthermore, our study suggests that specific components of the aposematic signal (i.e., dorsal color, ventral color, and spotting pattern) are affected differently by natural and sexual selection.     

Homologies in the colour patterns of the genus Charaxes (Lepidoptera: Nymphalidae)

The phylogenetically and morphologically diverse patterns of Charaxes can be reduced to a simple set of pattern elements which can be homologized throughout the genus. At least five types of correspondence (homologies) exist among pattern elements: those between (1) species, (2) forewing and hindwing, (3) dorsal and ventral wing surface, (4) serial wing-cells, and (5) individual pattern elements within a single wing-cell. Differences in Charaxes colour patterns result from the distortion, elaboration, enlargement, reduction or loss of individual pattern elements. Further variation is often the result of dislocation of pattern elements from their serial homologues in neighbouring wing-cells, and fusion of individual pattern elements to create larger areas of colour. The type of analysis presented in this paper should be broadly applicable within the Lepidoptera and may prove useful in studying the systematics of colour patterns and the evolution of the developmental system that gives rise to them.     

Vibration receptive sensilla on the wing margins of the silkworm moth Bombyx mori

Bristles along the wing margins (wm-bristles) of the silkworm moth, Bombyx mori, were studied morphologically and electrophysiologically. The male moth has ca. 50 wm-bristles on each forewing and hindwing. Scanning electron microscopy revealed that these wm-bristles are typical mechanosensilla. Leuco-methylene blue staining demonstrated that each wm-bristle has a single receptor neuron, which is also characteristic of the mechanosensillum. The receptor neuron responded to vibrating air currents but did not respond to a constant air current. The wm-bristles showed clear directional sensitivity to vibrating air currents. The wm-bristles were classified into two types, type I and type II, by their response patterns to sinusoidal movements of the bristle. The neuron in type I discharged bursting spikes immediately following stimulation onset and also discharged a single spike for each sinusoidal cycle for frequencies less than ca. 60 Hz. The neuron in type II only responded to vibrations over 40 Hz and, specifically at 75 Hz, discharged a single spike for each sinusoidal cycle throughout the stimulation period. These results suggest that the two types of wm-bristles are highly tuned in different ways to detect vibrations due to the wing beat. The roles of the wm-bristles in the wing beat are discussed.     

Eyespots deflect predator attack increasing fitness and promoting the evolution of phenotypic plasticity

Some eyespots are thought to deflect attack away from the vulnerable body, yet there is limited empirical evidence for this function and its adaptive advantage. Here, we demonstrate the conspicuous ventral hindwing eyespots found on Bicyclus anynana butterflies protect against invertebrate predators, specifically praying mantids. Wet season (WS) butterflies with larger, brighter eyespots were easier for mantids to detect, but more difficult to capture compared to dry season (DS) butterflies with small, dull eyespots. Mantids attacked the wing eyespots of WS butterflies more frequently resulting in greater butterfly survival and reproductive success. With a reciprocal eyespot transplant, we demonstrated the fitness benefits of eyespots were independent of butterfly behaviour. Regardless of whether the butterfly was WS or DS, large marginal eyespots pasted on the hindwings increased butterfly survival and successful oviposition during predation encounters. In previous studies, DS B. anynana experienced delayed detection by vertebrate predators, but both forms suffered low survival once detected. Our results suggest predator abundance, identity and phenology may all be important selective forces for B. anynana. Thus, reciprocal selection between invertebrate and vertebrate predators across seasons may contribute to the evolution of the B. anynana polyphenism.     

Prey from the eyes of predators: Color discriminability of aposematic and mimetic butterflies from an avian visual perspective

Predation exerts strong selection on mimetic butterfly wing color patterns, which also serve other functions such as sexual selection. Therefore, specific selection pressures may affect the sexes and signal components differentially. We tested three predictions about the evolution of mimetic resemblance by comparing wing coloration of aposematic butterflies and their Batesian mimics: (a) females gain greater mimetic advantage than males and therefore are better mimics, (b) due to intersexual genetic correlations, sexually monomorphic mimics are better mimics than female‐limited mimics, and (c) mimetic resemblance is better on the dorsal wing surface that is visible to predators in flight. Using a physiological model of avian color vision, we quantified mimetic resemblance from predators’ perspective, which showed that female butterflies were better mimics than males. Mimetic resemblance in female‐limited mimics was comparable to that in sexually monomorphic mimics, suggesting that intersexual genetic correlations did not constrain adaptive response to selection for female‐limited mimicry. Mimetic resemblance on the ventral wing surface was better than that on the dorsal wing surface, implying stronger natural and sexual selection on ventral and dorsal surfaces, respectively. These results suggest that mimetic resemblance in butterfly mimicry rings has evolved under various selective pressures acting in a sex‐ and wing surface‐specific manner.     

The startle responses of blue jays to Catocala (Lepidoptera: Noctuidae) prey models

Artificial moth models were presented to caged blue jays, Cyanocitta cristata, in order to investigate the effectiveness of deimatic displays in underwing (Catocala: Noctuidae) moths. The models had flexible, patterned ‘hindwings’ which were concealed behind cardboard ‘forewings’ until the birds removed them from a presentation board. Jays which had been trained on models with grey hindwings exhibited a startle response when they were exposed to Catocala-patterned hindwings. In contrast to this, subjects trained on Catocala models did not startle to a novel grey hindwing. The startle response to Catocala patterns lasted over several days until birds habituated to the models. When the jays had habituated to one Catocala hindwing pattern, a novel Catocala pattern always elicited a startle response. Familiar Catocala hindwing patterns which appeared in an anomalous context (i.e., associated with a different forewing pattern) also evoked a startle response from these birds. Novelty, oddity, conspicuousness, and anomaly are considered as possible stimulus characteristics which trigger the startle response.     

Reorganization of sensory regulation of locust flight after partial deafferentation

Previous investigations have shown that the flight motor pattern of the mature locust (Locusta migratoria L.) relies heavily on the input of the hindwing tegulae. Removal of the hindwing tegulae results in an immediate change in the motor pattern: the wingbeat frequency (WBF) decreases and the interval between the activity of depressor and elevator muscles (D–E interval) increases. In contrast, removal of the forewing tegulae has little effect on the motor pattern. Here we report adaptive modifications in the flight system that occur after the removal of the hindwing tegulae. Over a period of about 2 weeks following hendwing tegula removal, the flight motor pattern progressively returned towards normal, and in about 80% of the animals recovery of the flight motor pattern was complete. We describe the changes in the activity pattern of flight muscles and in the patterns of depolarizations in flight motoneurons and flight interneurons associated with this recovery. In contrast to the situation in the intact animal, the activity of the forewing tegulae is necessary in recovered animals for the generation of the motor pattern. Removal of the forewing tegulae in recovered animals resulted resulted in similar changes in the flight motor pattern as were observed in intact animals after the removal of the hindwing tegulae. Furthermore, electrical stimulation of forewing tegula afferents in recovered animals produced similar resetting effects on the motor pattern as electrical stimulation of the hindwing tegulae afferents in intact animals. From these observations we conclude that recovery is due to the functional replacement of the removed hindwing tegulae by input from the forewing tegulae.     

Morpho morphometrics: Shared ancestry and selection drive the evolution of wing size and shape in Morpho butterflies

Butterfly wings harbor highly diverse phenotypes and are involved in many functions. Wing size and shape result from interactions between adaptive processes, phylogenetic history, and developmental constraints, which are complex to disentangle. Here, we focus on the genus Morpho (Nymphalidae: Satyrinae, 30 species), which presents a high diversity of sizes, shapes, and color patterns. First, we generate a comprehensive molecular phylogeny of these 30 species. Next, using 911 collection specimens, we quantify the variation of wing size and shape across species, to assess the importance of shared ancestry, microhabitat use, and sexual selection in the evolution of the wings. While accounting for phylogenetic and allometric effects, we detect a significant difference in wing shape but not size among microhabitats. Fore and hindwings covary at the individual and species levels, and the covariation differs among microhabitats. However, the microhabitat structure in covariation disappears when phylogenetic relationships are taken into account. Our results demonstrate that microhabitat has driven wing shape evolution, although it has not strongly affected forewing and hindwing integration. We also found that sexual dimorphism of forewing shape and color pattern are coupled, suggesting a common selective force.     

Acoustic startle/escape reactions in tethered flying locusts: motor patterns and wing kinematics underlying intentional steering

We simultaneously recorded flight muscle activity and wing kinematics in tethered, flying locusts to determine the relationship between asymmetric depressor muscle activation and the kinematics of the stroke reversal at the onset of wing depression during attempted intentional steering manoeuvres. High-frequency, pulsed sounds produced bilateral asymmetries in forewing direct depressor muscles (M97, 98, 99) that were positively correlated with asymmetric forewing depression and asymmetries in stroke reversal timing. Bilateral asymmetries in hindwing depressor muscles (M127 and M128 but not M129) were positively correlated with asymmetric hindwing depression and asymmetries in the timing of the hindwing stroke reversal; M129 was negatively correlated with these shifts. Hindwing depressor asymmetries and wing kinematic changes were smaller and shifted in opposite direction than corresponding measurements of the forewings. These findings suggest that intentional steering manoeuvres employ bulk shifts in depressor muscle timing that affect the timing of the stroke reversals thereby establishing asymmetric wing depression. Finally, we found indications that locusts may actively control the timing of forewing rotation and speculate this may be a mechanism for generating steering torques. These effects would act in concert with forces generated by asymmetric wing depression and angle of attack to establish rapid changes in direction.Abbreviations ASR acoustic startle response - dB SPL decibel sound pressure level (re: 20 Pa RMS) - EMG electromyogram - FWA forewing asymmetry - HWA hindwing asymmetry     

A new genus Heppneralis Park of Lecithoceridae (Lepidoptera: Gelechioidea) from Is. Sulawesi,Indonesia, with descriptions of two new species

A new genus, Heppneralis Park, gen. nov., of the subfamily Torodorinae, is described based on the type species, H. decorella sp. nov., and an additional new species, H. dumogaensis sp. nov., from Is. Sulawesi, Indonesia is described. The new genus is distinguished from all known genera of the subfamily by unique wing color markings on both wings, with R₅ and M₂ absent in the forewing and M₂ absent in the hindwing.     

Reorganization of sensory regulation of locust flight after partial deafferentation.

Previous investigations have shown that the flight motor pattern of the mature locust (Locusta migratoria L.) relies heavily on the input of the hindwing tegulae. Removal of the hindwing tegulae results in an immediate change in the motor pattern: the wingbeat frequency (WBF) decreases and the interval between the activity of depressor and elevator muscles (D-E interval) increases. In contrast, removal of the forewing tegulae has little effect on the motor pattern. Here we report adaptive modifications in the flight system that occur after the removal of the hindwing tegulae. Over a period of about 2 weeks following hindwing tegula removal, the flight motor pattern progressively returned towards normal, and in about 80% of the animals recovery of the flight motor pattern was complete. We describe the changes in the activity pattern of flight muscles and in the patterns of depolarizations in flight motoneurons and flight interneurons associated with this recovery. In contrast to the situation in the intact animal, the activity of the forewing tegulae is necessary in recovered animals for the generation of the motor pattern. Removal of the forewing tegulae in recovered animals resulted in similar changes in the flight motor pattern as were observed in intact animals after the removal of the hindwing tegulae. Furthermore, electrical stimulation of forewing tegula afferents in recovered animals produced similar resetting effects on the motor pattern as electrical stimulation of the hindwing tegulae afferents in intact animals. From these observations we conclude that recovery is due to the functional replacement of the removed hindwing tegulae by input from the forewing tegulae.     

Hox基因与昆虫翅的特化

自从1978年E.B. Lewis描述了著名的果蝇双胸突变体（bithorax）以来,大量的比较发育遗传学研究为我们揭示了形态进化的遗传基础,从而使形态进化研究进入了一个新的时代。同时,Hox基因的研究也成为这一领域的焦点。本文综述了昆虫翅的起源及其特化类群翅的发育遗传学研究的最新进展。一般认为,原始的有翅昆虫胸腹部多附肢（包括翅）; 之后不同的体节受到了不同Hox的抑制,形成两对翅以及前后翅的分化; Ubx的不同表达导致了前后翅的分化,并且Ubx负责识别后翅。我们选择翅特化最为显著的3个类群——鞘翅目（T2鞘翅）、双翅目（T3平衡棒）和捻翅目（T2平衡棒）,结合Hox的表达情况讨论了翅的特化机理。目前已知双翅目和鞘翅目的翅的控制模式存在巨大差异,两种模式的比较研究对于理解翅的形态进化具有重要的意义。但是对捻翅目昆虫的研究则很少。