Critical Photoperiod Inducing Diapause in Lygus Hesperus

Lygus hesperus were reared under daylengths ranging from 10:14 to 13:11 [L:D] h.  Resulting diapause response was described by a logistic function.  Females were more responsive than were males but the critical photoperiod (photoperiod resulting in 50% of the maximal observed diapause response) was about 12 h for both sexes.  Incidence of diapause increased only slightly at photoperiods shorter than 11 h.  Maximal response was only about 80% for females and about 60% for males.  The L. hesperus population in Central Arizona appears less responsive to short daylengths than is the population in the San Joaquin Valley of California.