Date of Award

1984

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Entomology

Abstract

Cattle hoofprint samples from a permanent pasture in Vermilion Parish, Louisiana during 1980 yielded an average of 9.2 eggs and capsules of Psorophora columbiae (Dyar and Knab)/hoofprint. Pasture sections differed significantly (P < .0001) in number of eggs and capsules/hoofprint. Sections ranged from 2.7 to 20.6 eggs and capsules/hoofprint. The number of eggs and capsules collected/date also differed significantly (P < .01), but peaks in numbers did not always correspond with peaks in rainfall or adult mosquito collections. Hoofprint densities and herd movement did not influence egg distribution. Estimates of numbers of eggs and capsules on the 30 ha permanent pasture range from 2,633,621 in late February to 16,913,025 on June 2, 1980. Mosquito oviposition was compared in hoofprint samples taken from a permanent pasture and a fallow rice field in Vermilion Parish, Louisiana during 1981. Hoofprints from the permanent pasture contained significantly (P < .001) more Ps. columbiae eggs than did hoofprints from the fallow rice field, averaging 3.3 and 1.9 eggs/hoofprint respectively. However, estimates of egg density in the 2 sites did not differ significantly (P > .05) since hoofprint density was greater in the fallow rice field. Egg density estimates were 15.2/m('2) for the fallow rice field and 13.3/m('2) for the permanent pasture. Hoofprint depth, hoofprint location, and cattle movement did not influence egg distribution. Results of studies with caged Ps. columbiae exposed to natural lighting conditions indicated that the oviposition cycle was bimodal with the main peak occurring in the 2 h period following sunset. This period coincides with peaks in flight activity, feeding activity, and swarming reported for this species in earlier studies. Caged Ps. columbiae were exposed to soil that contained various percentages of moisture by weight. Average numbers of eggs deposited per cage in soil at 0, 20, 40, 60, and 80% moisture and in water differed significantly (P < .004) with 2.2, 30.2, 89.8, 28.3, 14.0, and 43.2 eggs/moisture level respectively. Cages of mosquitoes exposed to soil at 30, 40, 50, 60, 70, and 80% moisture by weight deposited 125.8, 188.6, 176.9, 39.6, 46.3, and 31.5 eggs/moisture level respectively. These averages were significantly different (P < .008).

Pages

115

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