The effect of photoperiod on the flight activity and biology of Rhyzopertha dominica (Coleoptera: Bostrichidae)

Abstract

Patterns of Rhyzopertha dominica (F.) biology were studied at photoperiods of 16:8, 14:10, 12:12, 10:14, 8:16, and 6:18 (L:D). Aspects of biology studied included flight activity of a lab and field strain, and oviposition, egg hatch, developmental time and larval-pupal survival for the lab strain. Egg hatch and larval-pupal survival were unaffected by photoperiod. The longest scotophase significantly delayed development, increased egg production and reduced flight. Oviposition was highest at 8:16. Young females at all photoperiods had a higher rate of oviposition than older females. Flight occurred primarily throughout the photophase, and the number of flights did not var^ with sex. Flight activity of 3and 6-day-old adults was significantly higher than that of 9-day-old adults. Adults from the field strain flew more frequently than those from the lab strain. Time of day did not affect the flight patterns of lab-strain adults, but field-strain adults flew more frequently in the first 2 hr of the photophase at all photoperiods. Based on photoperiod alone, this study suggests that young R. dominica should tend to fly more in the summer during wheat harvest and oviposit more in the late fall, winter and early spring. Effects of photoperiod on the seasonality of stored-product insect biology rarely have been studied. This limited interest is perhaps because of the general con ception that stored-product environments are constantly dark or artificially light ed. Stamopoulos (1989) studied the effects of photoperiods on several aspects of the biology of Acanthoscelides obtectus Say. A long scotophase increased fecundity, egg hatch, and the number and weight of emerging adults, and decreased larval mortality and developmental time. Cymborowski and Giebultowicz (1976) found that a 12 L.12 D photoperiod reduced developmental time of Ephestia kuehniella Zell. by three days compared with development under constant darkness. The time of year that several species of stored-product pyralid moth pests diapause can be determined by photoperiod (Cox and Bell, 1991). These studies indicate that seasonal variation in photoperiod can influence the biology of stored-product insects in situations of natural light exposure. Rhyzopertha dominica (F.) is a major pest of stored grain that shows seasonal flight patterns (Fields et al., 1993) and is commonly trapped in the field away from masses of stored grain (Cogburn, 1988). For this species, photoperiod has been shown to affect daily flight patterns (Leos-Martinez et al., 1986) and response to an aggregation pheromone (Obeng-Ofori and Coaker, 1990). Pajni and Shobha (1979) showed that R. dominica tends to fly in the light and oviposit in the dark. They also suggested that this species may have a reproductive diapause. Therefore, the objective of our study was to examine the effect of photoperiod on flight 1 Faculty of Agricultural and Food Sciences, American University, Beirut, Lebanon. 2 U.S. Grain Marketing Research Laboratory, USDA-ARS, 1515 College Avenue, Manhattan, Kan sas 66502. 3 Author to whom all correspondence should be addressed. Accepted for publication 29 September 1993. This content downloaded from 157.55.39.136 on Tue, 05 Jul 2016 05:06:31 UTC All use subject to http://about.jstor.org/terms 108 JOURNAL OF THE KANSAS ENTOMOLOGICAL SOCIETY