Feeding Adaptations of Some Predaceous Hemiptera

Feeding adaptations in five species of predaceous heteropterans (Geocoris punctipes (Say), Nabis alternatus Parshley, Podisus maculiventris (Say), Zelus renardii Kolenati and Sinea confusa Caudell) representing four families (Lygaeidae, Nabidae, Pentatomidae, and Reduviidae) were studied. Mouthparts were examined with scanning electron and light microscopy. Radio-labeled (14C) inulin was used to determine that preoral digestive enzymes originate in the salivary glands rather than the gut. All species tested positive for proteinase and phospholipase, but only N. alternatus and P. maculiventris tested positive for salivary amylase. Evidences of salivary stylet collars were observed in all five species, and flanges were studied in detail in G. punctipes and appear to be related to leverage for stylets. Direct observations and video replays showed that the toothed mandibular stylets penetrate, rasp, and cut prey tissues; maxillary stylets form salivary and food canals that deliver saliva and remove liquified prey contents from within. Movements of invading stylets within prey as they probe narrow recesses, such as legs and antennae, are amazingly quick and agile, sometimes bending back upon themselves. These morphological, physiological, and behavioral adaptations permit a concerted pre-digestion of prey from within and allow these predators to feed efficiently upon prey that equal or exceed them in size.