Patterns of habitat use by generalist predators in agricultural ecosystems

Densities of hemipteran and coccinellid predators were measured in soybeans, corn, tomatoes and tobacco. Each predator species preferred a subset of the four crops. Nabis spp. (Hemiptera: Nabidae) were most abundant in soybeans; Geocoris punctipes (Hemiptera: Lygaeidae) preferred soybeans and tobacco; Orius insidiosus (Hemiptera: Anthocoridae) preferred soybeans and corn; and Jalysus wickhami (Hemiptera: Berytidae) preferred tomatoes and tobacco. The two most common coccinellids, Coleomegilla maculata and Hippodamia convergens, preferred corn and tobacco, respectively. Harmonia axyridis, Coccinella septempunctata, and Cycloneda munda preferred tobacco.; Within-plant distribution of predators was determined in the same crops. Nabis spp. and Geocoris punctipes nymphs occupied lower portions of soybean plants than did adults. Geocoris punctipes was associated with stems, petioles, blooms and fruits, while nabids were on the foliage. In corn, Coleomegilla maculata was distributed over the whole plant. Hippodamia convergens, H. axyridis, C. septempunctata, and J. wickhami occurred near the top of tomatoes, while C. maculata occurred at a lower level. In tobacco, H. convergens, H. axyridis, C. septempunctata and J. wickhami occurred throughout the plant, while C. maculata and G. punctipes were primarily on dead and senescing lower leaves.; In pairwise choice tests with a soybean standard, the order of oviposition preference for N. roseipennis was squash {dollar}>{dollar} soybean = tobacco {dollar}>{dollar} tomato {dollar}>{dollar} corn. Eggs were laid at significantly greater height within soybean and squash plants than within corn, tomato, and tobacco plants.; Studies of C. maculata, H. convergens, and H. axyridis on diets of tobacco aphids vs. corn pollen showed that all three species survived and developed well on an aphid diet. Survival and development in these three species were hindered by feeding exclusively on pollen, but least so for C. maculata.; Two- and three-trophic-level effects of resistant plants on development of N. roseipennis were determined. Resistant plants negatively affected development time, adult weight, and fecundity through herbivore prey which had fed on resistant plants, but not through direct plant feeding by the predator.; Predators of lepidopteran eggs and temporal patterns of predation were determined in soybeans, corn and tomatoes. Nabids were the dominant predators in soybeans and primarily nocturnal. Coleomegilla maculata was the dominant predator in corn and they were diurnal. Few predators were observed in tomatoes.; In an ancillary study reported in an appendix, Podisus maculiventris (Hemiptera: Pentatomidae) was shown to make directional choices relative to vibrations produced by feeding by the green cloverworm, Plathypena scabra (Lepidoptera: Noctuidae). Podisus maculiventris moved toward the source of real and recorded vibrations.