Date of Award:

5-1-1982

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Department name when degree awarded

Life Sciences:Biology

Committee Chair(s)

B. Austin Haws

Committee

B. Austin Haws

Committee

Donald W. Davis

Committee

Frederic H. Wagner

Abstract

The activity of selected arthropod predators on both immature and adult black grass bugs, Labops hesperius Uhler and Irbisia brachycera Uhler, in infested Utah ranges was investigated. Adult Nabis alternatus was found to the most important predator of black grass bugs, especially in early spring, when nabids were the most abundant predaceous species. Immature nabids consumed the bugs but because of their smaller size they preyed mostly on leafhoppers, smaller plant bug nymphs and other immature nabids. A shortwinged species of Nabis (probably N. vanduzeei) showed good potential as a predator of adult Labops and Irbisia in laboratory feeding tests. Several spiders were found to be important predators of black grass bugs. Their importance increased as the spiders grew in size. In decreasing order of importance as predators were the thomicids Xysticus cunctator, Misumenops lepidus and Tibellus sp.; the clubionid Castianera sp.; and the tetragnathidae, Tetragnatha sp. It was concluded from field and laboratory observations, that spiders are opportunistic predators and that they will attack any prey in relative similar size range, including beneficial arthropods, such as nabids and other spiders. Wolf spiders (lycosids) and Thanatus sp. (thomisid), both commonly observed in the field and collected during early spring, failed to prey on black grass bugs in the 1982 laboratory tests. Thanatus appeared to prefer prey other than black grass bugs, like flies, leafhoppers, other plant grass bugs, etc. The failure of wolf spiders as predators of immature Labops or Irbisia in the 1982 laboratory tests could be due to "nervousness", making them difficult to handle. They were affected by confinement. Studies should utilize large containers, trying to simulate conditions similar to a grassland.

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