Technical Abstract: This study is the first to quantify and statistically analyze the stylet probing/penetration behaviors of Lygus bugs, and the external body movements associated with both probing and non-probing, via electrical penetration graph [EPG] and video recording, respectively. We also provide here the first complete system of organization and terminology for non-sequential EPG parameters. These parameters foster a deep understanding of the meanings and relationships among EPG waveforms. Widespread adoption of these terms will allow standardization in EPG research. Our EPG and video data reveal for the first time the stylet penetration behaviors of nymphal L. hesperus that cause cotton square damage, and the mechanism involved. L. hesperus nymphs spent only one-third of their time on squares probing; the remainder was spent standing motionless in place, grooming, or in sensory exploration. While probing, two-thirds of their time was spent in laceration/salivation and one-third in ingestion. Thus, L. hesperus nymphs actively spread out numerous, minute injections of their macerating watery saliva, deeply drilled /lacerated into all parts of the developing square. After injection of saliva within the square, the insect then stands and waits for solubilization of the square’s cell contents, and then quickly ingests the slurry. The extensive laceration by the stylets may, secondarily, potentiate salivary maceration by mechanically rupturing cell walls. The plant responses to such behavior are thus summarized as ‘mechanical cell rupture-enhanced maceration.’