The pink bollworm can overwinter above 30 latitudes because it enters diapause which arrests development at the fourth instar. The trigger for diapause was shown to be photoperiod, although diet and temperature play a role as well (Ankersmit and Adkisson, 1967). Diapause larvae weigh more, use oxygen less, have lower heartbeat rates and males have smaller testes than their non-diapause counterparts (Adkisson, et al., 1963).

The diapause condition of the pink bollworm is tenuous. Diapause can be initiated by subjecting postfeeding fourth instar larvae to a day length of 1:1 light:dark or lower for just a few days. In addition, the diapause can be broken just as readily, so that diapausing larvae, terminate diapause and continue development. Two conditions known to cause diapause termination besides switching to a 14:10 light:dark regime, are physical disturbance and flooding. Other parameters such as diet and temperature also influence diapause, but photoperiod is the major determining factor (Adkisson, 1961; Adkisson, et al., 1963).

Traditional methods of determining diapause are strictly empirical. Fourth instar larvae are kept for one month. Those that have not pupated are considered to be in diapause. The number of animals entering diapause can depend on handling protocols. We reinvestigated this procedure in cooperation with Bud Beasley during 1990 by using a new procedure. An ELISA (enzyme linked immunosorbant assay) test was developed based on the antibodies raised to pectinophorin. Pectinophorin is the so-called diapause associated protein in pink bollworm resent in the hemolymph only during diapause.