Development of Nymphs and Feeding Habits of Nymphal and Adult Edessa meditabunda (Heteroptera: Pentatomidae) on Soybean and Sunflower

Abstract

Most Edessa meditabunda (F.) nymphs feeding on several plant parts of soybean, Glycine max (L.) Merrill, and on sunflower, Helianthus annuus L., did not reach adulthood. Nymphs did not reach the third stadium on reproductive structures, such as soybean pod or seed or on sunflower seed (mature). On immature sunflower seed and stems, and on soybean stems, nymphal mortality was 100%. On soybean leaves, 20% of the nymphs reached the adult stage; on sunflower leaves and stems, only 5% completed nymphal development. Developmental time (second to fifth stadia) varied from 42.0 to 78.0 d, values greater than observed in most seed-sucking pentatomids (20–34 d). Nymphs preferred soybean stems or leaves to pods. On sunflower, nymphs preferred fruit, leaves, and stems, in that order. Adults clearly preferred to feed on soybean stems. Curiously, adult E. meditabunda were usually found head-down, rather than in the “normal” position (head-up), while feeding on soybean stems. Its rostrum is much shorter than that of phytophagous pentatomids specialized for feeding on seeds. Feeding frequency indicated by the number of stylet sheaths found on the food (soybean leaflet) varied among stadia and among individuals within a stadium. The number of stylet sheaths per stadium and per stadium-day increased as the nymphs developed, indicating greater feeding activity by older nymphs.