Pear psylla, Cacopsylla pyricola (Förster) (Hemiptera: Psyllidae), is a pest of pears, Pyrus L. (Rosaceae), throughout North America and western Europe. Previous studies in our laboratory showed that males of the overwintering form (winter morphotype) were attracted to volatile chemicals from pear shoots infested with post-diapause females. The current study shows that males of the summer morph...