Thermoregulation and flying habits of the Japanese sulfur butterfly Colias erate (Lepidoptera: Pieridae) in an open habitat

This study evaluated the impact of the thermal environment on the flying behavior of male Japanese sulfur butterflies Colias erate searching for females in an open habitat. Thoracic temperature was monitored before and after flight. Mean thoracic temperature of butterflies immediately after landing was consistently higher than, but independent of, ambient temperature. Although ground speed of flying butterflies was different between flight types, air speed against the butterfly was similar across flight types. The excess of thoracic over ambient temperature was lower in flying butterflies than in basking ones, as predicted by a model. This difference appeared to be due to air current, which enhanced heat loss. In a laboratory study, newly eclosed male butterflies were placed under an incandescent lamp to measure their thoracic temperature at different air current speeds. The excess of thoracic over ambient temperature decreased as the speed of air currents increased. When the air current was similar to the air speed against flying butterflies in the field, a substantial decrease occurred in the operative thoracic temperature.     

Pterin pigments amplify iridescent ultraviolet signal in males of the orange sulphur butterfly, Colias eurytheme

Animal colouration is typically the product of nanostructures that reflect or scatter light and pigments that absorb it. The interplay between these colour-producing mechanisms may influence the efficacy and potential information content of colour signals, but this notion has received little empirical attention. Wing scales in the male orange sulphur butterfly (Colias eurytheme) possess ridges with lamellae that produce a brilliant iridescent ultraviolet (UV) reflectance via thin-film interference. Curiously, these same scales contain pterin pigments that strongly absorb wavelengths below 550 nm. Given that male UV reflectance functions as a sexual signal in C. eurytheme, it is paradoxical that pigments in the wing scales are highly UV absorbing. We present spectrophotometric analyses of the wings before and after pterin removal that show that pterins both depress the amplitude of UV iridescence and suppress a diffuse UV reflectance that emanates from the scales. This latter effect enhances the directionality and spectral purity of the iridescence, and increases the signal's chromaticity and potential signal content. Our findings also suggest that pterins amplify the contrast between iridescent UV reflectance and scale background colour as a male's wings move during flight.     

Iridescent ultraviolet signal in the orange sulphur butterfly (Colias eurytheme): spatial, temporal and spectral properties

Many of nature's most striking animal colours are iridescent, exhibiting a high degree of spectral purity and strong angular dependence of intensity and hue. Although a growing number of studies have detailed the intricate mechanisms responsible for producing iridescent colours, few attempts have been made to describe their dynamic appearance in ecologically and behaviourally realistic contexts. We suggest that the optical properties unique to iridescent structural colours are important for understanding how they function as signals during behavioural interactions. Using males of the orange sulphur butterfly, Colias eurytheme , which exhibit an iridescent ultraviolet (UV) reflectance on their dorsal wing surfaces, we develop a holistic framework for inferring the appearance of this signal to conspecifics under field conditions that incorporate data on their spectral sensitivity. We show that, during flight, the UV signal is brightest within a wing beat cycle when viewed from directly above the male. Spectral properties of the signal under natural lighting indicate that male wing colour should be readily perceived and distinguished from that of females and from the dark green visual background of UV-absorbing vegetation. Finally, our analyses permit predictions regarding how signal senders and receivers should orientate themselves for maximal transmission and reception of this ultraviolet iridescent signal.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 349–364.     

A review of the pre-oviposition behaviour of small cabbage white butterfly, Pieris rapae(lepidoptera: Pieridae)

This paper reviews the literature concerning the ovipositional behaviour of Pieris rapae (small cabbage white butterfly) and where appropriate considers results from studies involving other butterflies. The paper considers searching behaviour, stimuli utilised in host plant finding and identification and concludes with a general section on the role of learning and prior experience in ovipositional behaviour.     

The eyes of a patrolling butterfly: visual field and eye structure in the Orange Sulphur, Colias eurytheme (Lepidoptera, Pieridae)

Sensory information plays a critical role in determining an animal's behavior on both proximate and evolutionary timescales. Butterflies, like many other insects, use vision extensively over their lifetimes, and yet relatively little work has been published to date on their visual capabilities. We describe the visual system of a pierid butterfly, Colias eurytheme, with the ultimate goal of better understanding its role in shaping the behavior of this animal. We made several measurements: visual field dimensions, eye surface area, interommatidial angle (Deltaphi), facet diameter (D), and eye parameter (p). C. eurytheme had a large visual field and considerable regional variation in visual acuity, as inferred by Deltaphi and D. When compared to females, males had larger eye surface areas, smaller Deltaphi, and larger D in all regions except ventrally. Both sexes had proportionally large eye surface areas compared to other butterflies. Minimum p in males was small, indicating that some regions of their eyes may operate close to the diffraction limit. Finally, we found that both eye surface area and D scaled positively, but with negative allometry to body size. We discuss the relevance of these visual characteristics to the biology and behavior of C. eurytheme.     

Effects of saline intake on spermatophore and sperm ejaculation in the male swallowtail butterfly Papilio xuthus (Lepidoptera: Papilionidae)

Although sodium ions induce puddling behavior in males of some butterfly species, the role of sodium ions in male life history is unclear. Newly emerged laboratory‐reared males of the swallowtail butterfly Papilio xuthus were allocated to five adult diets: water (as a control) and 0.001, 0.01, 0.1 or 1 mol/L saline solution. Males preferred to take 0.1 mol/L saline solution. We attempted to hand‐pair males after two days of intake. Males on all diets, except those taking 1 mol/L saline solution, were likely to couple. Males taking 0.01 mol/L saline solution produced the largest spermatophore, although there were no significant differences in the number of eupyrene sperm bundles and apyrene spermatozoa between saline‐taking males and control males. Salt accumulation in the male body also had little effect on the number of both types of spermatozoon in the spermatophore.     

Habitat use and population biology of the Danube Clouded Yellow butterfly Colias myrmidone (Lepidoptera: Pieridae) in Romania

The Danube Clouded Yellow (Colias myrmidone) is one of the most endangered butterflies in Europe. Its distribution range shrank dramatically in the last few decades due to the extinction of populations in Western and Central Europe. Ecological studies were commenced when populations were already at the verge of extinction, thus our knowledge on the population ecology and habitat use of this butterfly is very limited. Here we report the results of a study on habitat preferences, egg distribution and demography of C. myrmidone in Romania, perhaps the last remaining stronghold of the species in Central Europe. We found that Danube Clouded Yellow adults occurred mainly in mesophilous grasslands created by forest clearing and then maintained by low intensity grazing allowing bushes and forest-edge vegetation to develop and host Chamaecytisus species to grow. Butterflies highly preferred lightly grazed pastures over hay meadows and abandoned grasslands, their density was positively related to host plant density. Egg-laying females preferred habitat patches with relatively high cover of the host plant and tall vegetation. Both apparent survival rate and encounter probability were lower for females than males, and parameter estimations also had much higher errors for females. These indicate that much higher sampling effort is needed to estimate and monitor population parameters for females than for males. Our results provide guidelines for the habitat management and population monitoring of Colias myrmidone, thus may significantly contribute to its successful conservation.     

Juvenile hormone titers in virgin and mated Choristoneura fumiferana and C. rosaceana females: assessment of the capacity of males to produce and transfer JH to the female during copulation

We used a radioimmunoassay (RIA) to assess the effect of mating on juvenile hormone (JH) titer in females of the tortricid moths Choristoneura fumiferana and C. rosaceana. Virgins had undetectable levels of JH in their hemolymph on the 5th day of the pupal stage but titers rose to 1-4 and 0.2-0.5 ng JH II eq./ml, respectively, after emergence. On days 1, 3 and 5 following copulation, females of both species had higher JH titers than virgins of the same ages, with the greatest difference between virgin and mated females observed on day 3 for C. fumiferana and on day 5 for C. rosaceana. This increase was apparently not the result of a male-to-female transfer of JH during copulation since: (i) the accessory sex glands (ASGs) of males of both species displayed a very limited ability to convert JH acid into JH, (ii) ASGs produced no JH when incubated in vitro in the presence of L-[methyl-(3)H]-methionine, (iii) ASGs of males injected with L-[methyl-(3)H]-methionine 24 h prior to dissection contained no JH-associated radioactivity, and (iv) freshly formed spermatophores dissected out of females mated to similarly injected males contained no trace of radioactive JH. In addition, the JH content of ASGs and spermatophores, as measured by RIA, was not higher than that of virgin-female hemolymph, on a per-mg basis. However, in contrast with earlier findings in other species of moths, the CA of male C. fumiferana and C. rosaceana maintained in vitro in the presence of tritiated methionine produced and released JH I, JH II and JH III in quantities and proportions similar to those reported for female glands.     

Cues by which suspended-leaf nests of Euryattus (Araneae: Salticidae) females are recognized by conspecific males and by an aggressive-mimic salticid, Portia fimbriata

Females of Euryattus sp. indet, a salticid from Queensland, suspend rolled-up leaves for nests. Euryattus males respond to conspecific females in nests with vibratory courtship. Portia fimbriata , a sympatric salticid that preys on Euryattus , responds to Euryattus females' nests by mimicking the courtship of Euryattus males. In the laboratory, cues by which potential mates (conspecific males) and potential predators ( P. fimbriata females) recognize the nests of Euryattus females are investigated experimentally. Both the position of the leaf in relation to the substratum and the number of threads between the leaf and the substratum appear to be important cues by which both the Euryattus males and P. fimbriata females find nests. In addition, chemical cues from Euryattus females influence conspecific males, but there is no evidence that chemical cues are important to the predator.     

Epigamic selection by males as evidenced by courtship partner preferences in the checkered white butterfly (Pieris protodice)

Free-flying males of the checkered white butterfly, Pieris protodice, were presented with tethered females that varied with respect to both size (as measured by forewing length) and age (as measured by wing wear). Because males make a substantial investment in their offspring through nutrients passed to the female during copulation, they were expected to court young and large females for longer times than older and smaller females, and they did so. Additional experiments further suggest that size discriminations are made on the basis of apparent wing area and age discriminations are made on the basis of an age-related increase in ultraviolet reflectance that occurs in females. The discussion examines the adaptive value of these discriminations.     

Seasonal effects of density on territory occupation by males of the satyrine butterfly Paryphthimoides phronius (Butler 1867)

Territorial defense in butterflies may be related to both population density and climatic conditions. If these factors change throughout the year, males are expected to adaptively adjust their behavior in order to maximize reproductive success. In this study, we analyzed the annual dynamics of territory occupation by males of the satyrine butterfly Paryphthimoides phronius at a mildly seasonal subtropical site in southeastern Brazil. We investigated the relationship between the number of defended sites, number of males disputing mating areas, proportion of males adopting alternative mate-locating tactics, and the proportion of time invested in territorial disputes with annual variations in temperature and male density. We found little support for the influence of temperature on the dynamics of territory occupation. On the other hand, the number of defended sites increased with male density, whereas the number of males inside each territory, the proportion of satellite males, and the proportion of time spent in territorial disputes were unrelated to variations in population abundance. Territory defense seems to be adopted whenever possible. We conclude that, instead of increasing the number of individuals disputing the same territory during months of high population abundance, males apparently opt to colonize and defend new and, maybe, suboptimal areas.     

TErritorial defence and mating success in males of the small heath butterfly, coenonympha pamphilus L. (Lepidoptera: Satyridae)

It has long been recognized that territorial defence in male butterflies must be some sort of mating strategy and that the territories are used as mating stations. However, so far, no systematic study has established the adaptive significance of territorial behaviour. This study is an attempt to fill this gap. By comparing the distribution of territories with the distribution of locations where wild and released virgin females mated this study shows that, in the small heath butterfly (Coenonympha pamphilus), males in territories have higher mating success than males outside territories. This supported the hypotheses that the function of territorial behaviour is to secure more matings and that the territories are mating stations. Wing length measurements suggest the same. Large males residing in territories tended to mate more often than small males, which were usually found outside territories. Since resident males were larger than non-resident males, this size difference was used to see how territorial occupancy influenced longevity. Mark-recapture of measured males revealed no significant correlation between wing length and the further life expectancy of males, strongly suggesting that the mating success of males in territories is also higher when measured over their whole lifetime.     

Degradation of wool by Hofmannophila pseudospretella (lepidoptera: Oecophoridae) larval midgut extracts under conditions simulating the midgut environment

The ability of midgut extracts of the keratinophagous larva, Hofmannophila pseudospretella (Lepidoptera: Oecophoridae), to catalyse degradation of wool was studied in vitro. A high rate of degradation was observed under anaerobic conditions in the presence of a reducing agent at pH 9.2 and at an oxidation-reduction potential of −200 to −350 mV, values comparable to those observed in vivo. Rates were sensitive to the oxidation-reduction potential and the nature of the reductant, being higher for sulphydryl compounds than for other sulfur-based reducing agents and inversely related to the oxidation-reduction potential for both classes of compounds. Degradation was measured as a two-step process involving reduction/solubilization of wool proteins followed by proteolysis. The initial step was shown to occur via two pathways, enzymic and non-enzymic. The enzymic pathway was the major route in vitro and was characterized by a requirement for a heat-unstable, high molecular weight fraction of the larval midgut extract as well as a reducing agent for maximum rates. The possible nature of this activity and its in vivo importance are discussed. © 1996 Wiley-Liss, Inc.     

Lifetime mating success of males in a natural population of the papilionid butterfly,Atrophaneura alcinous (Lepidoptera: Papilionidae)

Lifetime mating success of males in a natural population of the papilionid butterfly, Atrophaneura alcinous, was investigated and causes of the variation were examined. The most successful males mated with 5 females, whereas about 73% of the males failed to mate. Body size of males was not correlated with their eclosion date, longevity and lifetime mating success. There was no trade-off between mating success and longevity, and long-lived males had a disproportionately high mating success. Although number of available females per male per day was not variable among males with different longevities, long-lived males had higher mating efficiency. Time interval between matings by non-virgin males was shorter than that from eclosion to the first mating. High lifetime mating success of long-lived males was strongly related to their mating experience, not to their age per se.     

A range-wide genetic bottleneck overwhelms contemporary landscape factors and local abundance in shaping genetic patterns of an alpine butterfly (Lepidoptera: Pieridae: Colias behrii)

Spatial and environmental heterogeneity are major factors in structuring species distributions in alpine landscapes. These landscapes have also been affected by glacial advances and retreats, causing alpine taxa to undergo range shifts and demographic changes. These nonequilibrium population dynamics have the potential to obscure the effects of environmental factors on the distribution of genetic variation. Here, we investigate how demographic change and environmental factors influence genetic variation in the alpine butterfly Colias behrii. Data from 14 microsatellite loci provide evidence of bottlenecks in all population samples. We test several alternative models of demography using approximate Bayesian computation (ABC), with the results favouring a model in which a recent bottleneck precedes rapid population growth. Applying independent calibrations to microsatellite loci and a nuclear gene, we estimate that this bottleneck affected both northern and southern populations 531–281 years ago, coinciding with a period of global cooling. Using regression approaches, we attempt to separate the effects of population structure, geographical distance and landscape on patterns of population genetic differentiation. Only 40% of the variation in F_ST is explained by these models, with geographical distance and least‐cost distance among meadow patches selected as the best predictors. Various measures of genetic diversity within populations are also decoupled from estimates of local abundance and habitat patch characteristics. Our results demonstrate that demographic change can have a disproportionate influence on genetic diversity in alpine species, contrasting with other studies that suggest landscape features control contemporary demographic processes in high‐elevation environments.     

Adaptation at specific loci. VII. Natural selection,dispersal and the diversity of molecular-functional variation patterns among butterfly species complexes (Colias: Lepidoptera,Pieridae)

Natural genetic variants at the phosphoglucose isomerase, PGI, gene differ in spatial patterning of their polymorphism among species complexes of Colias butterflies in North America. In both lowland and alpine complexes, molecular-functional properties of the polymorphic genotypes can be used to predict genotype-specific adult flight performances and resulting large genotypic differences in adult fitness components. In the lowland species complex, there is striking uniformity of PGI polymorph frequencies at a number of sites across the American West; this fits with earlier findings of strong, similar differences in fitness components over this range. In an alpine complex, Colias meadii shows similar uniformity of PGI frequencies within habitat types, either montane steppe or alpine tundra, over several hundred kilometres in the absence of dispersal. At the same time, large shifts (10-20%) in frequency of the most common alleles occur between steppe and tundra populations, whether these are isolated or, as in some cases, are in contact and exchange many dispersing adults each generation. Data on male mating success of common C. meadii PGI genotypes in steppe and tundra show heterozygote advantage in both habitat types, with shifts in relative homozygote disadvantage between habitats which are consistent with observed frequency differences. Nonadaptive explanations for this situation are rejected, and alternative, thermal-ecology-based adaptive hypotheses are proposed for later experimental test. These findings show that strong local selection may dominate dispersal as an evolutionary agent, whether or not dispersal is present, and that selection may often be the major force promoting 'cohesion' of species over long distances. This case offers new opportunities for integrating studies of molecular structure and function with ecological aspects of natural selection in the wild, both within and among species.     

Sperm reflux and its role in multiple mating in males of a butterfly Polygonia c-aureum Linnaeus (Lepidoptera: Nymphalidae)

The relationship between sperm quantity in the duplex and that in the vasa deferentia was examined in the Asian comma butterfly, Polygonia c-aureum. In virgin males, the number of eupyrene sperm bundles in the duplex increased linearly with age, whereas that in the vasa deferentia was consistently small. However, numerous sperm were found in the vasa deferentia of males immediately after mating. The number of eupyrene sperm bundles in the vasa deferentia after mating significantly increased with age and with increasing the time interval between matings. From these and other results, it was suggested that some sperm in the duplex were moved back to the vasa deferentia during mating, and that such sperm reflux provides a means to save sperm for multiple mating.     

Identification,accumulation, and biosynthesis of the cuticular hydrocarbons of the southern armyworm,Spodoptera eridania (cramer) (lepidoptera: Noctuidae)

The accumulation and biosynthesis of cuticular and internal hydrocarbons in the Southern armyworm, Spodoptera eridania, were examined at closely timed intervals during larval and pupal development. Gas chromatography-mass spectrometry (GC-MS) was used to identify n-alkanes, monomethylalkanes, and dimethylalkanes ranging in chain length from 23 to 35 carbons. The amount of cuticular hydrocarbon stayed relatively constant during each stadium, while the amount of internal hydrocarbon increased dramatically during the first half of each larval stadium, presumably to replace the cuticular hydrocarbon lost on the shed cast skin with each molt. The accumulation of internal hydrocarbon was mirrored by large increases in the rate of incorporation of labeled acetate into the hydrocarbon fraction. Hydrocarbon production fell to very low rates during the latter part of the fourth and fifth larval stadia. Relatively high rates of hydrocarbon production were observed during the first and last one-third of the pupal stage and essentially all of the hydrocarbons produced during this stage remained internal. These data document large changes in the rates of hydrocarbon production during development in S. eridania and suggest that most of the hydrocarbon produced during each stage was stored internally and then transported to the cuticle of the next stage.