The evolutionary significance of dry and wet season forms in some tropical butterflies

An explanation is developed for the adaptive significance of the forms characteristic of the dry season and wet season adult generations of some tropical butterflies. The divergent phenotypes are accounted for as adaptive responses to a shift in the optimum balance between dependence on the alternative (but interdependent) strategies of active anti-predator devices and of crypsis. The seasonal polyphenisms exhibited by the satyrines Melanitis leda (Fabricius) and Orsotrioena medus (Fabricius) and the nymphalid Junonia almana (Linné) are examined in detail. The wet season forms show prominent marginal eyespot patterns which are displayed at rest and function principally in the deflection of attacks by vertebrate predators. In contrast, the dry season forms show very small or no spots and are wholly cryptic. Wet season butterflies are more active in general than those in the dry season when aestivation behaviour is often observed. The alternative phenotypes represent responses to the differences in behaviour, environment and nature of predation. Reproductive success is optimized in each season by an interaction of phenotype and behaviour. The hypothesis must be tested in detail by an investigation of the behavioural ecology and population biology of particular species. It is argued that these seasonal polyphenisms provide examples of adaptations to a repeating pattern of changing environments where the mode of selection is, in broad terms, understood.     

Flight speed of male spruce bud worm moths in a wind tunnel at different wind speeds and at different distances from a pheromone source

ABSTRACT. Flying male spruce budworm ( Choristoneura fumiferana [Clem.]) moths responding to virgin females and to synthetic pheromone in a wind tunnel maintained a constant rate of upwind progress when held by moving optomotor cues at a constant distance from the pheromone source. When allowed to progress upwind to the source, however, they slowed their upwind speed progressively as they approached it. They also adjusted their flight speed to maintain similar rates of upwind progress at different wind speeds.     

Anthropologies of art

This paper discusses how different conceptions of the idea of ‘anthropology’ entail different views of the ‘anthropology of art’. The prevailing notion of anthropology as the Western study of small-scale non-Western societies leads to a conception of the anthropology of art as dealing with the visual arts of these societies or cultures. Anthropology is sometimes also interpreted as referring to a particular approach that is applicable in examining sociocultural phenomena in whatever culture, including its art forms. Both conceptions of anthropology may be considered subsidiary to a more encompassing view of anthropology as the multidisciplinary study of humankind. Following this view, the anthropology of art becomes the comprehensive examination of art in human existence. As such it would coincide with World Art Studies, conceived as the global and multidisciplinary study of the visual arts.     

To feed or to wrap? Female silk cues elicit male nuptial gift construction in a semiaquatic trechaleid spider

By wrapping prey and offering it as a nuptial gift, males can obtain mating and/or parental benefits despite some costs. Males of the Neotropical semiaquatic spider Paratrechalea ornata (Trechaleidae) offer females a nuptial gift consisting of a prey item wrapped in silk. What stimulus inhibits males from feeding and elicits gift construction? We hypothesized that signals associated with female silk threads could affect decision-making by males. We investigated three groups of males carrying a captured prey under different experimental treatments. In the treatment S, males were exposed to an arena with female silk; in SF, males were exposed to both silk and a female confined in a cell, and in the control group, males were exposed to a clean arena. Gift construction was observed only in the S and SF groups, with a similar occurrence rate. After touching females (SF group), males did not change their pattern of gift construction. Gift construction occurrence increased with male and female age. The results lead us to assume that the existence of chemical cues associated with female silk elicits male searching behaviour and gift construction, allowing males to decide between eating or wrapping prey according to the possibility of a sexual encounter. Anticipating gift construction, males are ready to mate, diminishing the risks of predation, female desertion or male–male scramble competition. The effect of age on behavioural variation and the rate of construction is discussed.     

Reverse hierarchies and sensory learning

Revealing the relationships between perceptual representations in the brain and mechanisms of adult perceptual learning is of great importance, potentially leading to significantly improved training techniques both for improving skills in the general population and for ameliorating deficits in special populations. In this review, we summarize the essentials of reverse hierarchy theory for perceptual learning in the visual and auditory modalities and describe the theory's implications for designing improved training procedures, for a variety of goals and populations.     

Evolution and spectral tuning of visual pigments in birds and mammals

Variation in the types and spectral characteristics of visual pigments is a common mechanism for the adaptation of the vertebrate visual system to prevailing light conditions. The extent of this diversity in mammals and birds is discussed in detail in this review, alongside an in-depth consideration of the molecular changes involved. In mammals, a nocturnal stage in early evolution is thought to underlie the reduction in the number of classes of cone visual pigment genes from four to only two, with the secondary loss of one of these genes in many monochromatic nocturnal and marine species. The trichromacy seen in many primates arises from either a polymorphism or duplication of one of these genes. In contrast, birds have retained the four ancestral cone visual pigment genes, with a generally conserved expression in either single or double cone classes. The loss of sensitivity to ultraviolet (UV) irradiation is a feature of both mammalian and avian visual evolution, with UV sensitivity retained among mammals by only a subset of rodents and marsupials. Where it is found in birds, it is not ancestral but newly acquired.