Date of Award

Spring 1974

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

Program/Concentration

Biology

Committee Director

Daniel E. Sonenshine

Committee Member

Gerald F. Levy

Committee Member

Robert L. Ake

Call Number for Print

Special Collections LD4331.B46 G367

Abstract

Elements of the ecology of the two dominant man-biting ticks were studied during 1971-1973 in two locations in Southeastern Virginia, namely, what is now the Dismal Swamp National Wildlife Refuge and Newport News City Park. Tick species composition, relative abundance, density, and distribution in the two areas were compared. In addition, the Dismal Swamp locality was used as a test area for studies on the survival of native, lab reared and translocated Dermacentor variabilis (Say) and Amblvomma americanum (L.) in relation to selected abiotic factors. The Newport News locality served as a control area for these studies.

The species composition of ticks captured by flagging and host examination was as expected for this geographical region. In the Dismal Swamp, the most abundant species of tick was the American dog tick, D. variabilis, which was found throughout the area sampled. The second most abundant species, the lone star tick, A. americanum, however, was concentrated only in specific locations. Ixodes scaoularis (Say) and Haemaohvsalis leoorisoalustris (Packard) were also found in rare instances, but the sampling methods utilized precluded speculation on their abundance.

Isolated colonization by D. variabilis of a suboptimal habitat via artificial openings (roads and ditches) is suggested by the highly significant density variation observed between the roadside and forest interior concentrations of this tick in the Dismal Swamp. In 1971 flagging of 39,100 m2 demonstrated a density of 15 D. variabilis/1000 m2 from the forest-road ecotone. In contrast flagging of 2500m2 of the forest interior indicated a density of only 1.2 D. variabilis/1000 m2. In 1972, density of 37 D. variabilis adults/1000 m2 was found along the roadside while a density of only 1.5 D. variabilis adults/1000 m2 was found within the forest interior during a total seasonal flagging effort covering 180,200 m2. A. americanum comprised only 3-6% of the total captive for the 2 years in the Dismal Swamp.

No significant difference between roadside and forest interior densities of A. americanum adults was found at Newport News (113/1000 m2 vs 107/1000 m2 respectively) during a seasonal flagging effort of 17,800 m2.

Survival and molting of adults and nymphs of laboratory reared A. americanum and D. variabilis and wild caught A. americanum were tested in environmental containers at two sites in the Swamp and one site in Newport News. The survival at 80% and molting at 94% were greatest for all ticks at Newport News ~ Survival and molting were much lower at the Dismal Town site (51% and 84% respectively), while few ticks survived and molted at the Lynn Ditch site (14% and 49% respectively). The time required to complete molting in the 2 Swamp sites was more than twice that of the laboratory controls. This tended to increase their vulnerability to adverse physical factors as well as predators.

The abiotic factor of most significance was found to be inundation. Over 60% of those areas surveyed were inundated for 6 or more weeks during the winter months. Inundation did not occur until after the ticks had gone into diapause. Overwinter survival studies of ticks in inundated sites showed death within 8 days of submersion. Diapausing ticks made no observable effort to move from the substrate chosen for quiescence, even after inundation.

Hosts for all stages of D. variabilis and A. americanum were observed. Limited data on these hosts suggest that they are very sparsely distributed. Wildlife management may alter this host-support system of these ticks, permitting a change in their populations.

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DOI

10.25777/6p1c-4277

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