Physiological age-grading and ovarian physiology of Prostephanus truncatus

Abstract. The reproductive tracts of male and female Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) were described for beetles between emergence and 30 days old in order to determine age-grading criteria. Seminal vesicles were bigger among non-mated males than among mated males due to accumulation of sperm; no age-specific differences were found for male P. truncatus. Ovaries (germarium size, number of follicles and follicle size) were similarly developed for females between 5 and 30 days old and did not differ between mated and non-mated females. Starved females were found to resorb follicles. Yellow body formation was strongly dependent on age, and was used as an age-grading criterion for female P. truncatus. Females flying off maize cobs and caught with pheromone traps were of varying physiological age and mated, and their ovarian development was suspended. All migrating females were mated, indicating that lone females may act as colonizers, independently of males. The applicability of migration theories to P. truncatus and adaptive inter-reproductive dispersal as part of its life history strategy are discussed.