The reproductive organs, sexual behaviour, and pheromone glands of Costelytra zealandica (White) (Coleoptera: Scarabaeidae), and Phthorimaea operculella (Zeller) (Lepidotera: Gelechiidae)

Abstract

Separate studies concerning reproduction were made of Costelytra zealandica (White) (Scarabaeidae: Melolonthinae), and of Phthorimaea operculella (Zeller) (Gelechiidae: Gnorimoschemini). In C. zealandica sexual dimorphism was described; the male and female external genitalia were described in more detail than previously; an account was given of the muscles of the external genitalia and of the mechanics of copulation; and the first description was provided of the morphology and histology of the internal reproductive organs. The latter were shown to differ from these of other Scarabaeidae in only a few minor respects. In addition the accessory glands of the female were described and a preliminary identification of the contained bacteria was carried out. The first account of the sexual behaviour of C. zealandica was given and the influences of environmental factors on both this and flight were noted. In addition, sexual attraction was investigated in the field: extracts of females were found to be attractive to males and confirmation was obtained that phenol attracts males. The sex attractant was demonstrated to be most effective when located near the edges of tall edible plants where the beetles swarm. In P. operculella, sexual dimorphism, and the morphology and histology of the internal reproductive organs were described for the first time. The latter were found to show close similarities with these of various other Lepidoptera. In addition, the male and female external genitalia were described in more detail than previously. The sexual behaviour of P. operculella was described for the first time and the time of day when this moth is sexually active was investigated both in the field and laboratory. It was shown that the time when mating occurs is determined by the female releasing her sex pheromone whereas the male will respond at any time although this is maximal when the female is attractive. An objective and quantitative laboratory bioassay was developed for the female sex pheromone of P. operculella and this was used to conclusively demonstrate the presence of a female sex pheromone and to show that it is produced in the middle third of the ovipositor. A histological examination confirmed that the pheromone gland is a dorsal sac-like region of the intersegmental membrane between the 9th and 10th abdominal segments on the ovipositor. The male pheromone glands were shown by histological methods to be located on the hindwings, and an indication was obtained that their scent subdues the escape reactions of females prior to copulation. Finally, the morphology, histology, and ultrastructure of male and female pheromone glands were described and compared with these of other Lepidoptera.