Thesis (M.D.)--University of Pennsylvania, 1803. / Microform version available in the Readex Early American Imprints series.

The catalpa sphinx, Ceratomia catalpae, is a specialist on Catalpa trees, which produce iridoid glycosides (IGs). Whereas some trees are defoliated every year, others escape herbivory. Caterpillar populations are either heavily parasitized by the braconid wasp, Cotesia congregata, or remain unparasitized. We hypothesized that these patterns could be explained by variable IG concentrations among trees and insect responses to these chemicals. IG concentrations varied among trees. Percent defoliation was positively related to IG concentration. In comparisons of insect responses to relatively high or low IG concentrations, moths preferred to oviposit on trees with high IG concentrations. Caterpillars did not display a feeding preference nor did wasps differ in searching responses to leaf discs with high or low IG concentrations. Results indicate that observed patterns of herbivory can be explained by moth oviposition preferences for trees with high IG concentrations.

This study addresses flood risk assessment in the Catalpa Creek watershed, located in northeast Mississippi, USA. Employing the Hydrological Modeling System (HEC-HMS) and the River Analysis System (HEC-RAS), integrated models were developed and calibrated, to predict flood behavior within the watershed. The study conducted flood frequency analyses for return periods ranging from 2 to 100 years and generated flood inundation maps, pinpointing flood-prone areas. Mitigation measures for flood risk management were recommended. The results underscore the effectiveness of the integrated modeling approach for simulating and understanding the complex dynamics of flood events. The research identified critical flood-prone zones, emphasizing the importance of proactive flood risk management. The calibrated hydrological model serves as a valuable tool for stormwater management, water resource planning, and watershed assessment. The study provides insights into flood risk in the Catalpa Creek watershed, offering valuable guidance to regional decision-makers. This study lays the foundation for future investigations in floodplain encroachment, sediment transport, stream restoration, and flood inundation hazard mapping.

Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) is a polyphagous, invasive, and highly significant pest of mid-Atlantic fruit orchards. Its capacity to invade orchards season-long is believed to be facilitated by the availability of wild host plants near orchards and the high dispersal capacity of adults and nymphs. Interactions between H. halys and its hosts were investigated via laboratory and field experiments. Rearing H. halys nymphs in the laboratory on several of its known wild and tree fruit hosts used alone and in combination showed that peach was much more suitable for nymphal development and survival than was apple, tree of heaven, or catalpa and that nymphal performance was enhanced on mixed host diets. Nymphs reared on different host plant diets yielded adults that differed in protein, sugar or lipid content, offering new insights into plant diet effects on H. halys nutrition. The majority of tree species identified from unmanaged woodlands next to apple orchards in Virginia and West Virginia were known hosts of H. halys. Passive trunk traps were developed to capture H. halys nymphs walking up and down tree trunks and used to measure their temporal patterns of movement onto and off of wild and tree fruit hosts at the orchard-woodland interface via weekly assessments during two consecutive seasons. More upward- than downward-walking nymphs were captured, which may be partially explained by the positively phototactic and negatively geotactic behavior of H. halys nymphs demonstrated in laboratory studies. Most nymphs captured while walking up and down trunks were second instars, although the data also reflected temporal changes in the distribution of instars and temporal variation in the numbers of nymphs captured. A field study to characterize injuries to apple and peach fruit at harvest from feeding by young or older nymphs early or late in the season revealed that feeding by young nymphs early in the season resulted in least injury to both crops. In combination, these studies greatly improve our understanding of the biology and ecology of H. halys in eastern fruit orchards and provide relevant data that will inform the development of ecologically-based management programs for it. / Ph. D.