Members of the Miridae (Lygus lineolaris Palisot de Beauvois and Pseudatomoscelis seriatus Reuter) and Pentatomidae (Acrosternum hilare Say, Euschistus servus (Say), Euschistus tristigmus (Say), Euschistus quadrator Rolston, Oebalus pugnax (F.), Piezodorus guildinii (Westwood), and Thyanta custator accerra McAtee) comprise a piercing—sucking insect complex that continues to plague multiple crops, including cotton. All these species have been associated with pathogen transmission. Breaching of boll carpel walls facilitates introduction of pathogens, and it is unknown whether stylets of these pests can fully penetrate carpel walls. Thus, stylet penetration estimates are needed and have been the focus of the present work. Stylet penetration estimates for L. lineolaris were significantly deeper than P. seriatus. Among the Pentatomidae, highest mean penetrationwas estimated for E. servus followed by A. hilare, yet A. hilare possessed a longer rostrum. Similarly, O. pugnax showed deeper penetration estimates than P. guildinii yet P. guildinii possessed a longer rostrum. Thus, rostrum length should not be equated to penetration potential. Pseudatomoscelis seriatus and L. lineolaris both infest early-season cotton, and the ranges of observed penetration indicate these insects, as well as the Pentatomidae, can breach the walls of critical pinhead squares and smaller bolls. The insects addressed herein affect a myriad of crops globally, and penetration estimates allow identification of growth stages susceptible to feeding and disease transmission.