The ecology, life history, and population dynamics of the sagebrush defoliator, Aroga websteri Clarke, were studied in the field and laboratory. The defoliator has one generation a year at the Curlew Valley site. It overwintered in the egg stage and passed through five larval instars. Ten parasite species attacked the defoliator at the study site . Four species, Orgilus ferus, Phaeogenes sp., Spilochalcis leptis, and Apanteles cacoeciae, contributed over 75 percent of the total incidence of parasitism. Parasitism ranged from 20 to 76 percent in 1971, but only ranged from 6 to 29 percent in 1972. This decrease in total parasitism in 1972 coincided with a five-fold increase in the defoliator population. In 1972, many mature larvae died as a result of food shortage. A microsporidian infection and a predaceous beetle also caused variable mortality during the two years. Methods for determining defoliation to sagebrush plants were also studied in the field.
The consumption and utilization of food by the fourth and fifth larval instars were determined. The fecundity, rate of development, and behavior of the insect were also investigated under laboratory conditions. Partial life tables were constructed from the findings of 1971 and 1972 to assess the r ole of various mortality factors in regulating the sagebrush defoliator numbers.
| Identifer | oai:union.ndltd.org:UTAHS/oai:digitalcommons.usu.edu:etd-4530 |
| Date | 01 May 1972 |
| Creators | Kirkland, Reed L. |
| Publisher | DigitalCommons@USU |
| Source Sets | Utah State University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | All Graduate Theses and Dissertations |
| Rights | Copyright for this work is held by the author. Transmission or reproduction of materials protected by copyright beyond that allowed by fair use requires the written permission of the copyright owners. Works not in the public domain cannot be commercially exploited without permission of the copyright owner. Responsibility for any use rests exclusively with the user. For more information contact Andrew Wesolek (andrew.wesolek@usu.edu). |
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