True UV color vision in a female butterfly with two UV opsins

ABSTRACT In true color vision, animals discriminate between light wavelengths, regardless of intensity, using at least two photoreceptors with different spectral sensitivity peaks. Heliconius butterflies have duplicate UV opsin genes, which encode ultraviolet and violet photoreceptors, respectively. In Heliconius erato, only females express the ultraviolet photoreceptor, suggesting females (but not males) can discriminate between UV wavelengths. We tested the ability of H. erato, and two species lacking the violet receptor, Heliconius melpomene and Eueides isabella, to discriminate between 380 and 390 nm, and between 400 and 436 nm, after being trained to associate each stimulus with a sugar reward. We found that only H. erato females have color vision in the UV range. Across species, both sexes show color vision in the blue range. Models of H. erato color vision suggest that females have an advantage over males in discriminating the inner UV-yellow corollas of Psiguria flowers from their outer orange petals. Moreover, previous models ( McCulloch et al., 2017) suggested that H. erato males have an advantage over females in discriminating Heliconius 3-hydroxykynurenine (3-OHK) yellow wing coloration from non-3-OHK yellow wing coloration found in other heliconiines. These results provide some of the first behavioral evidence for female H. erato UV color discrimination in the context of foraging, lending support to the hypothesis ( Briscoe et al., 2010) that the duplicated UV opsin genes function together in UV color vision. Taken together, the sexually dimorphic visual system of H. erato appears to have been shaped by both sexual selection and sex-specific natural selection.

Revised species definitions and nomenclature of the blue and purple/rose Cithaerias butterflies (Lepidoptera, Nymphalidae, Satyrinae)

This study reassesses the taxonomic status of Neotropical blue and purple/rose-colored Cithaerias butterflies, thus complementing a previous study of the rose-colored species. Based on comparative study of wing coloration and genitalia morphology, I revise species definitions and the taxonomic status of: Cithaerias andromeda, C. azurina STAT. REV., C. esmeralda STAT. REV., C. bandusia STAT. REV., C. pyropina, and C. songoana STAT. REV. Photographs of adults and illustrations of male and female genitalia are provided for all species. Of particular importance are the genitalia illustrations of male and female C. azurina, presented here for the first time, as well as finding a putative first female of Ecuadorean subspecies C. pyropina julia.

Minoa lutea Schwingenschuss, 1954 (Lepidoptera: Geometridae: Larentiinae) recognized as bona species

The species Minoa murinata (Scopoli, 1763) sensu lato is examined throughout its distribution range. Specimens from central Europe (Germany, Italy, France) are compared with those from Serbia, Croatia, Slovenia and newly collected specimens from eastern Turkey, Armenia, Georgia and Russia. The study is based on a combination of behavioural observations, morphological characters (size, wing coloration, structure of male and female genitalia) as well as genetic data (DNA barcoding). The taxon Minoa murinata var. monochroaria Herrich-Schäffer, 1848 is downgraded from subspecies rank to synonymy of M. murinata. Morphological study of the populations from eastern Turkey, Armenia, Georgia and Russia confirm the taxon Minoa murinata f./ssp. lutea Schwingenschuss, 1954 as a bona species. It is herewith upgraded from synonymy of M. murinata to species level. The results of DNA barcoding are discussed. Wing pattern, male and female genitalia of both species are illustrated.

True UV color vision in a butterfly with two UV opsins

ABSTRACTTrue color vision in animals is achieved when wavelength discrimination occurs based on chromatic content of the stimuli, regardless of intensity. In order to successfully discriminate between multiple wavelengths, animals must use at least two photoreceptor types with different spectral sensitivity peaks.Heliconius butterflies have duplicate UV opsin genes, which encode two kinds of photoreceptors with peak sensitivities in the ultraviolet and violet, respectively. In H. erato, the ultraviolet photoreceptor is only expressed in females.Evidence from intracellular recordings suggests female H. erato may be able to discriminate between UV wavelengths, however, this has yet to be tested experimentally.Using an arena with a controlled light setting, we tested the ability of H. erato, and two species lacking the violet receptor, H. melpomene and outgroup Eueides isabella, to discriminate between two ultraviolet wavelengths, 380 and 390 nm, as well as two blue wavelengths, 400 and 436 nm, after being trained to associate each stimulus with a food reward. Wavelength stimuli were presented in varying intensities to rule out brightness as a cue.We found that H. erato females were the only butterflies capable of color vision in the UV range; the other butterflies had an intensity-dependent preference for UV stimuli. Across species, both sexes showed color vision in the blue-range.Models of H. erato color vision suggest that females have an advantage over males in discriminating the inner UV-yellow corolla of Psiguria pollen flowers from the surrounding outer orange petals, while previous models (McCulloch et al. 2017) suggested that H. erato males have an advantage over females in discriminating Heliconius 3-hyroxykynurenine (3-OHK) yellow wing coloration from non-3-OHK yellow wing coloration found in mimics.These results provide some of the first behavioral evidence for UV color discrimination in Heliconius females in the context of foraging, lending support to the hypothesis (Briscoe et al. 2010) that the duplicated UV opsin genes function together in UV color vision. Taken together, the sexually dimorphic visual system of H. erato appears to have been shaped by both sexual selection and sex-specific natural selection.

Genomic architecture of a genetically assimilated seasonal color pattern

Developmental plasticity allows genomes to encode multiple distinct phenotypes that can be differentially manifested in response to environmental cues. Alternative plastic phenotypes can be selected through a process called genetic assimilation, although the mechanisms are still poorly understood. We assimilated a seasonal wing color phenotype in a naturally plastic population of butterflies (Junonia coenia) and characterized three responsible genes. Endocrine assays and chromatin accessibility and conformation analyses showed that the transition of wing coloration from an environmentally determined trait to a predominantly genetic trait occurred through selection for regulatory alleles of downstream wing-patterning genes. This mode of genetic evolution is likely favored by selection because it allows tissue- and trait-specific tuning of reaction norms without affecting core cue detection or transduction mechanisms.

Hot wings: thermal impacts of wing coloration on surface temperature during bird flight

Recent studies on bird flight propose that hotter wing surfaces reduce skin friction drag, thereby improving flight efficiency (lift-to-drag ratio). Darker wings may in turn heat up faster under solar radiation than lighter wings. We used three methods to test the impact of colour on wing surface temperature. First, we modelled surface temperature based on reflectance measurements. Second, we used thermal imaging on live ospreys ( Pandion haliaetus ) to examine surface temperature changes with increasing solar irradiance. Third, we experimentally heated differently coloured wings in a wind tunnel and measured wing surface temperature at realistic flight speeds. Even under simulated flight conditions, darker wings consistently became hotter than pale wings. In white wings with black tips, the temperature differential produced convective currents towards the darker wing tips that could lead to an increase in lift. Additionally, a temperature differential between wing-spanning warm muscles and colder flight feathers could delay the flow separation above the wing, increasing flight efficiency. Together, these results suggest that wing coloration and muscle temperature both play important roles in modulating wing surface temperature and therefore potentially flight efficiency.

Siccia imana, a new species from Rwanda (Lepidoptera: Erebidae: Arctiinae)

The genus Siccia Walker, 1854 is a member of the subtribe Cisthenina Bendib & Minet of the tribe Lithosiini Billberg (family Erebidae Leach, subfamily Arctiinae Leach) being widely distributed in the Afrotropics. Members of the genus are small or medium-sized moths with similar external appearance (whitish or grey wing coloration with blackish pattern consisting of spots and transverse lines). The check-list of the genus was provided by Kühne (2007), two additional species were described by Ivinskis & Saldaitis (2008). Currently the genus includes 20 valid species with very different male and female genitalia structures, and the generic and subgeneric structure of this group needs revision (Volynkin & László, in prep.).

Analysis of some morphological characters of Elzunia Bryk, 1937 (Nymphalidae: Danainae: Ithomiini) results in a revised classification

We propose a revised classification for the genus Elzunia Bryk, 1937, with four species and 20 subspecies. We describe two new subspecies, Elzunia humboldt carlosi Le Crom and Llorente, ssp. nov., and Elzunia humboldt willmotti Le Crom, Llorente and Andrade, ssp. nov. We recognize five additional unnamed subspecies but do not describe them because they are represented by too little material. A detailed examination of 854 specimens from 31 collections allowed us to define 24 stable phenotypes and delimit their geographic distribution. We present a diagnosis and description for each taxon and provide images of the wing coloration pattern and male genitalia, and a distribution map. We also present a key for all the species and subspecies. We conducted a multivariate statistical analysis of measurements of the discal cell (DC) veins, and with this we explore the species groupings by these characters. Lastly, we discuss mimetic interactions of this genus with species of other Ithomiini and Heliconiinae.