Population trends ofLygusspp. and 7 common insect predator groups were studied in strip-cut alfalfa during the summer of 1970 at Safford, Ariz. Adults ofLygusspp. andOrius tristicolor(white) consistently migrated to the half-grown alfalfa when the full-grown alfalfa was cut, but adults ofNabis, Collops, Geocoris, Chrysopa, reduviids, and coccinellids did not.Nymphs ofLygusandOriusdid not migrate to the half-grown alfalfa when the mature alfalfa was cut, resulting in high nymphal mortality in the cut areas. Possible migration of nymphs and larvae of other predator species occurred but was inconsistent.All species fluctuated in numbers as the season progressed except for adults ofGeocoris, which showed only a large early-season fluctuation.Zelus renardiiKolenati,Collops granellus(Fall),Scymnus, andHyperaspisspp. were also present but mostly in late summer.Orius tristicolorwas the most abundant predator, followed byNabis, Collops, Geocoris, Chrysopa, coccinellids, and reduviids.