Determination of parous rates in Phlebotomine sandflies with special reference to Amazonian species

Previous work on Phlebotomines has shown that most parous flies in many species may be recognised by the dark residual secretion in the accessory glands; parity can be confirmed by inspection of ovarioles. In the present study 12 species of Lutzomyia were caught in forests near Belém, Brazil, mainly with rodent-baited oil-traps. Many females of the predominant species, L. flaviscutellata (Mangabeira), were parasitised by the protozoan Monocystis. Parous rates based on examination of ovaries were subject to an error of about 5% due to diminution or disappearance of follicular relics. Two successive dilatations of the tunica were seen in L. davisi (Root), suggesting that it had laid two batches of eggs. Biting rates by parous flies varied little during the night, and were somewhat less than those of nullipars. In eight species the dark-gland rate approximated to the parous rate as shown by the ovaries; a small error may have been due to discharge of all secretion, disappearance of follicular relics and premature activity of glands. In contrast to this concordant pattern, four species showed discordance, possibly due to autogeny. It seems advisable to omit oil-trapped blood-fed flies when estimating parous rates by examining glands. Monocystis may increase the dark-gland rate, but it is non-pathogenic or has little effect on life span, and does not hinder blood-sucking.