No description available.

No description available.

No description available.

No description available.

Social learning is a well-studied process in vertebrates, yet insect social learning studies have historically neglected solitary insects. To bridge this gap, I investigated whether the fall field cricket, Gryllus pennsylvanicus, could use individual and social learning to associate water with visual and odour cues. Demonstrator crickets had firsthand experience sampling water paired with cues, and observer crickets watched the demonstrators. I therefore tested demonstrators for individual learning and observers for social learning. I tested for learning by measuring cue preference in the absence of water. When quantifying cue preference by the proportion of time spent near rewarded cues, there was no evidence of individual or social learning. However, when quantifying cue preference by the first cue investigation (>3 seconds) during the test, crickets showed evidence of individual but not social learning. There was also a small effect of cue type on learning. These results differ from previous studies that found social learning in other species of crickets. The findings highlight that there are interspecific differences in learning and social behaviour, and that the method of quantifying learning can influence the outcome.

No description available.

The amount of heritable variation and the pattern of genetic covariation in traits are the chief determinants in the evolution of a population, at least over the short term. A preponderance of heritability (h$ sp2)$ and genetic (r$ rm sb g)$ experiments are performed under laboratory conditions which are characterized by low levels of environmental variability. This thesis describes the investigation of the effects of environmental heterogeneity on phenotypic components of variance and covariance. Full-sib families of the field cricket, Gryllus pennsylvanicus, were split between a homogeneous laboratory environment and a more variable field environment. The values of h$ sp2$ were, on average, lower in the variable field environment, with a mean reduction of 19%. Development time was an exception, exhibiting high levels of additive variance in the field. Substantial decreases in generic components of variance contributed to the lower field h$ sp2$ estimates, as well as the expected increases in the components of environmental variance. Within-environment r$ rm sb g$ among morphological traits were not found to differ between the two environments. Laboratory measures of r$ rm sb g$ involving life history traits, though, were not found to reflect the same correlations measured in the heterogeneous environment. A significant negative genetic correlation between fecundity and development time was found in the field environment, yet was not observed in the laboratory. Male-female genetic correlations between morphological traits were high (all r$ rm sb g>0.73),$ and were consistently higher in the field environment than in the laboratory. The genetic correlations between the sexes in development time followed the same trend, but gonad weight showed no similarity between the sexes in either environment. Across-environment correlations within each trait are also discussed.

Thesis (Ph. D.)--University of Florida, 1988. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 149-153).

The present is an attempt to show the pattern of innervation, or neuronal geometry, of various nerves leading to their respective ganglia (Fig. 1) and to obtain visualization of the finest terminal branches. A description of the cellular arrangement of a segmental ganglion would be of value in better understanding the results obtained when using the axonal iontophoresis method applied to the third through seventh ventral nerve cord ganglia. A segmental ganglion of the thorax or abdomen is usually an oval mass of nerve tissue, continuous with the interganglionic connectives (Fig. A). Two or three principal lateral nerves extend from its sides. The ganglion is encased in a nucleated sheath, the neurilemma, which forms a continuous covering over the nerves and the connectives. The main cellular components of the ganglion, ganglion cells, are arranged peripherally, mostly in the lateral and dorsal parts. The central and ventral parts are occupied by a neuropil mass. The lateral nerves of the ganglion contain both motor and sensory fibers which arise from the dorsal and ventral roots, respectively, within the ganglion.

No description available.