Sexual Dimorphism in Eye Morphology in a Butterfly ( Asterocampa leilia

In the Empress Leilia butterfly, Asterocampa leilia, as in many insects, males have larger eyes than females. We explore the morphological causes and consequences of this dimorphism in eye size by comparing the corneal surface area, facet numbers, and patterns of variation in facet dimensions in males and females. We report that, with body size (measured by forewing length) controlled, male eyes are consistently larger than female eyes, and that, although males and females do not differ significantly in the number of facets per eye, males have significantly larger facets. Also, males have disproportionately larger facets both frontally and dorsally. As a result of these sexual differences in eye structure, males are expected to have a larger and more acute visual field than females which could be advantageous in the context of this species' mate searching tactic

A Comparative Study of Dragonfly Flight in Variable Oxygen Atmospheres

i ABSTRACT One hypothesis for the small size of insects relative to vertebrates, and the existence of giant fossil insects, is that atmospheric oxygen levels have constrained body sizes because oxygen delivery would be unable to match the needs of metabolically active tissues in larger insects. This study tested whether oxygen delivery becomes more challenging for larger insects by measuring the oxygen-sensitivity of flight metabolic rates and behavior during hovering for 11 different species of dragonflies that range in mass by an order of magnitude. Animals were flown in 7 different oxygen concentrations ranging from 30% to 2.5% to assess the sensitivity of their behavior and flight metabolic rates to oxygen. I also assessed the oxygen-sensitivity of flight in low-density air (nitrogen replaced with helium), to increase the metabolic demands of hovering flight. Lowered atmosphere densities did induce higher metabolic rates. Flight behaviors but not flight metabolic rates were highly oxygen-sensitive. A significant interaction between oxygen and mass was found for total flight time, with larger dragonflies varying flight time more in response to atmospheric oxygen. This study provides some support for the hypothesis that larger insects are more challenged in oxygen delivery, as predicted by the oxygen limitation hypothesis for insect gigantism in the Paleozoic. ii ACKNOWLEDGEMENT

MATING AND EGG MASS PRODUCTION IN THE AEOLID NUDIBRANCH HERMISSENDA CRASSICORNIS (GASTROPODA: OPISTHOBRANCHIA)

Volume: 165Start Page: 276End Page: 28

Production and Use of Secretions Passed by Males at Copulation in Pieris Protodice (Lepidoptera, Pieridae)

Volume: 91Start Page: 141End Page: 15

Temporal and spatial overlap in the mate-locating behavior of two species of Junonia (Nymphalidae)

Volume: 30Start Page: 267End Page: 27

Male-specific structures on the wings of the Gulf Fritillary butterfly Agraulis vanillae (Nymphalidae)

Volume: 57Start Page: 279End Page: 28

Female iridescent colour ornamentation in a butterfly that displays mutual ornamentation : is it a sexual signal?

In species wherein males display elaborate sexually selected traits or ornaments, conspecific females may also express these traits in full or partial form. This is called mutual ornamentation, and the co-occurrence of such traits in males and females remains poorly understood. In many sulphur butterflies (subfamily Coliadinae), males have a brilliant ultraviolet (UV) iridescence on their dorsal wing surfaces that functions as a sexual signal in courtship. In some of these sulphurs, such as the large grass yellow, Eurema hecabe, females also display dorsal iridescent patches, albeit smaller, restricted to the forewings and less bright than the male's, but the reasons for its occurrence in females are unknown. Here we present a study testing two functional hypotheses for the female UV-reflecting patch: an antiharassment hypothesis and a male mate choice hypothesis. The daily activity pattern of this species suggests that males are most likely to harass or choose among females from midday on. Observations made at this time of day on the characteristics of females related to male courtship duration suggest that males may preferentially court females with a large UV patch. Experiments with colour-manipulated models also suggest that males court with equal intensity females with and without a basal UV patch. Taken altogether the results provide no support for the antiharassment hypothesis. Because support for the male mate choice hypothesis was relatively weak and because of the limited potential for selection on female coloration due to male choice in these butterflies, the nonfunctional sexual correlation hypothesis remains a viable explanation for the female ornament.7 page(s