Feeding Behavior of Nezara viridula First Instars: EPG Analysis and Effect of Food Availability on Subsequent Development

Abstract

Assertions that first-instar pentatomids “do not feed” are pervasive in the literature. Recent research using rifampicin-resistant marked bacteria demonstrated that first-instar southern green stink bug, Nezara viridula (L.) (Hemiptera: Pentatomidae), ingest from green bean. The technique of electropenetrography (EPG), coupled with histology, has allowed researchers to elucidate feeding behavior within plant tissue, and recordings of several species (including N. viridula) have shown that internal stylet probes of adults and late-instar nymphs may terminate in xylem as well as in seed endosperm, inner pod wall, or stem parenchyma. The seeming contradiction regarding “feeding” could be explained if first instars were simply hydrating from plant tissue to maintain water balance. In this study, first-instar N. viridula were supplied with either water or green bean, and subsequently given a traditional rearing diet (green bean and peanut) from second instar onward. We noted aggregations of first instars forming on water wicks and on beans along the carpellary bundles and at both tips. Availability of food (green bean) in first instar did not affect subsequent development. Using EPG, we recorded first-instar N. viridula probing on soybean leaves and found the primary waveform to be xylem ingestion. Probing and ingestion behavior did not differ between first instars previously exposed to high and moderate humidity conditions. We conclude that these insects ingest from xylem, but nutrients other than water are not required in the first instar for successful nymphal development.