On the Life History and Habits of the Palm Weevil, Rhynchophorus palmarium

Abstract

In the laboratory, females deposited 245±155 eggs in an oviposition period of· 30.7±14.3 days, with maximum production of 48 eggs per day in the first 8–10 days of the period; maximum lifetime production was 718 eggs by a single female. The incubation period was 3.2±0.93 days at room temperature (70°–91°F) and humidity (62%–92%). There were 6–10 larval molts (most commonly 9), and the larval period averaged 52.0±10.0 days (as against 43.0±6.0 days for larvae reared in standing palms outdoors). Mature larvae spun cocoons in which they passed a prepupal stage of 4–17 days and a true pupal stage of 8–23 days (average for the two combined, 26.8±4.5 days), and in which the adults remained for 7.8±3.4 days before emerging. Feeding and mating normally began 12–24 hours after emergence, and oviposition commenced 5.6±3.7 days after the first mating; both sexes mated repeatedly and indiscriminately. The entire life cycle required 79.0±9.0 days in laboratory-reared insects, 72.0±13.0 days in insects reared in standing palms. The sex ratio was approximately 1:1, and adult longevity was 44.7±17.2 days for males, 40.7±15.5 days for females. Adults were most active at 5–7 PM and 7–11 AM. Both sexes were strong flyers, averaging about 20 ft per sec in the field, and were capable of rapid dissemination. Their rate of movement on coconut plantations varied from 85 yards to 1 mile in 24 hours, depending on conditions. Larval damage was most extensive in 3- to 7-year-old palms, whose “crowns” often fell over following excavation of the stem tissues by the larvae. Infestation was usually associated with red ring disease, of which the weevils were important vectors. Adult feeding and oviposition was observed in numerous palm species other than Cocos nucifera, as well as in several root and fruit crops.