Development of Diaprepes abbreviatus (Coleoptera: Curculionidae) on Artificial and Citrus Root Substrates

Abstract

Measurement of head capsule widths showed that larvae of D. abbreviatus generally have 10 or 11 instars when reared on artificial diet. The growth ratio for head capsules was j:reater during stadia for the I-5th instars and declined after the 6th. Head capsule widths and larval growth increased steadily for 71 d, at which time, all larvae were 7-10th instar. Larval growth reached a plateau at 114 d during stadia at 9-11th instar and remained unchanged to 188 d. The mean time for development of 1st to 7th instars was less compared with instars >7th. A frequency distribution based on head capsule size for greenhouse- and field-collected larvae fed citrus roots over time had similar stadia peaks to larvae reared on artificial diet in the laboratory. Weight of larvae with head capsule widths >1.0 mm increased slowly within stadia, whereas a greater increase in larval weight was observed for larvae with capsule widths >1.0 mm. Variation in larval weight for each stadium was also greater for larvae with head capsule widths >1.0 mm. Most larval weight gain occurred during stadia at 6-8th instar, suggesting higher food consumption at these developmental stages. Larval weight increased steadily within the initial 71 d but declined slowly thereafter. The mean weight for instars reared on artificial diet was greater than for either greenhouse- or field-collected larvae. The mean weight for larvae fed citrus roots in the greenhouse was smaller than for larvae feeding on roots in the field. On artificial diet, only a few larvae developed to pupae. Approximately 70% of the larvae pupated at the 10th instar, whereas others pupated at the 11th instar. The mean time ± SEM required for larval development to pupae, larvae to adult, and pupae to adult was 153.3 ±28.0 d, 158.3 ± 20.7 d, and 17 ± 3.8 d, respectively. Mean larval weight before pupation was 480.4 ± 102.5 mg, mean pupal weight 378.2 ± 66.1 mg, and mean adult weight 276.0 ± 51.6 mg. Larvae lost 20.3% of their live weight during metamorphosis to pupae and pupae lost 24.7% of their live weight in becoming adults.