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Diapause response to photoperiod in an Arizona population of Lygus hesperus (Hemiptera: Miridae)

D. W. Spurgeon, C. S. Brent
Journal of Entomological Science 2015 v.50 no.3 pp. 238-247
population, occurrence, rearing, males, models, plant pests, regression analysis, confidence interval, fat body, diapause, photoperiod, Lygus hesperus, incidence, eggs, females, adults, prediction, Arizona
The western tarnished plant bug (Lygus hesperus Knight) is an important crop pest in the western U.S. that overwinters in an adult diapause. However, knowledge of L. hesperus diapause is incomplete. Eggs from field-collected adults were reared under photoperiods of 10:14, 11:13, 12:12, and 13:10 (L:D) h at 26.7 ± 1 °C and the diapause response for each gender was modeled by a logistic function. Incidence of a novel fat body type was also examined by logistic regression. Validation studies using the same methods were subsequently conducted using photoperiods of 10.5:13.5, 11.5:12.5, and 12.5:11.5 (L:D) h. No effects of bug gender, photoperiod, or diapause status on occurrence of the novel fat type were detected. Estimates of diapause in validation studies were within confidence intervals for initial predictions, but systematic deviations from initial predictions prompted re-fitting of the models to include validation data. Re-fitted functions estimated critical photoperiods 11 h 44 min for females, and 11 h 21 min for males. The maximum incidence of diapause was lower for males than for females and was <100% for both genders. Re-fitted functions also predicted 50% of the population-specific maximum diapause response corresponded to photoperiods of 11 h 54 min (females) and 12 h 7 min (males). These results, combined with other recent findings, suggest heterogeneity in diapause response likely enables L. hesperus populations to adapt to local conditions. The estimated functions relating photoperiod to diapause incidence provide baselines to facilitate future studies of environmental and geographical influences on diapause in this species.