Ovipositional Preference and Distribution of Eggs in Selected Field and Vegetable Crops by Nabis roseipennis (Hemiptera: Nabidae)

Hemipteran predator abundance varies significantly among crop species. Ovipositional preference by these predators for specific crops may help explain differences in predator abundance among crops. Ovipositional preferences of Nabis roseipennis Reuter between a preferred standard (soybean) and four crops (corn, tomato, tobacco and squash) were determined in paired-choice tests under greenhouse conditions. Significantly more eggs or egg groups were found in soybean than in corn and tomato. Squash was the only plant preferred for oviposition over soybean. Within-plant distribution of eggs varied among plant species and appeared to be independent of prey distribution. The specific site chosen for oviposition in each plant species apparently was determined by plant physical characteristics, possibly including rind toughness and, for tomato and tobacco, glandular trichome presence and age. Patterns of ovipositional preference were similar to previous observations of field abundance and may be partially responsible for those patterns.

Movement of Nuclear Polyhedrosis Virus into Velvetbean Caterpillar (Lepidoptera: Noctuidae) Larval Populations on Soybean by Nabis roseipennis (Heteroptera: Nabidae) Nymphs

Nabis roseipennis Reuter nymphs that preyed on larvae of the nuclear polyhedrosis virus (NPV) infected velvetbean caterpillar, Anticarsia gemmatalis (Hübner), excreted the virus (AgNPV) for several days thereafter. Based on bioassays, fifth instar and second instar nymphs excreted 84.7 × 105 and 9.7 × 105 polyhedral inclusion bodies (PIB) per nymph, respectively. The AgNPV-contaminated nymphs effectively disseminated the virus via the feces over soybean plants where it served as inoculum to initiate disease in larval populations of A. gemmatalis caged in the field. Larval mortality from AgNPV ranged from 11.4 to 48.5% over treatments in two tests. Larval mortality in treatments where the source of virus inoculum was AgNPV-contaminated fifth instar nymphs was similar to that in treatments where the source of viral inoculum was diseased larvae. Larval mortality resulting from AgNPV dissemination by the nymphs was usually higher in treatments containing fifth instar nymphs than in those with second instar nymphs. Dissemination of NPV by fifth instar nymphs was higher in mixed-age than in uniformed-age A. gemmatalis larval populations. This was not the case with the smaller second instar nymphs.

FEEDING AND DEVELOPMENT OF NABIS ROSEIPENNIS (HEMIPTERA: NABIDAE) ON HELIOTHIS VIRESCENS (LEPIDOPTERA: NOCTUIDAE) LARVAE1

Feeding, development, and duration of life stages of Nabis roseipennis Reuter, on different size (2, 3, 4, or 5 mm) early instar Heliothis virescens (F.) larvae were studied in the laboratory. Three or 4-mm larvae were optimum for feeding, consumption, and development of nymphs and adults. Nabis roseipennis fed 3 or 4 mm larvae consumed more and survived longer than those fed 2 or 5 mm larvae. Prey size significantly affected the duration of the individual 5 nymphal stages. Nymphs fed 3 or 4 mm larvae developed faster than those fed 2 or 5 mm larvae. Nymphs feeding on 2 mm larvae did not develop to adults. Nymphs and adults can survive and mature satisfactorily for extended periods on small prey, but need larger prey to accelerate development and maintain a high growth potential.