This study is the first to statistically analyze the stylet probing/penetration behaviors of Lygus (Hemiptera: Miridae) bugs, and the external body movements associated with both probing and nonprobing, via electrical penetration graph (EPG) and videorecording, respectively. Behavioral quantification allows powerful statistical comparisons among host plants or other treatments. Thus, statistical analysis of data has played an important role in EPG research. However, few attempts have been made to standardize types and terminology used for statistical parameters. We provide here the first complete system of organization and terminology for nonsequential EPG parameters. 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 15% 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.”
