laboratory studies were conducted to compare rostrum length morphology of mandible serration and area of food and salivary canals of dichelops melacanthus (dallas) (dm), euschistus heros (f.) (eh), nezara viridula (l.) (nv), and piezodorus guildinii (westwood) (pg) (heteroptera: pentatomidae). nv showed the longest (5.9 mm) and pg the shortest (3.5 mm) rostrum length; dm and eh were intermediate. length and width of mandible tip areas holding serration was bigger for nv (106.0 and 30.2 μm, respectively) and smaller for pg (71.1 and 23.7 μm), with all species having four central teeth and three pairs of lateral teeth. the inner mandible surface showed squamous texture. cross-section of food and salivary canals (fc and sc) indicated greater area for nv and dm compared to eh and pg; however, the ratio fc/sc, yielded the highest relative area for pg.