Objective.Rhipicephalus sanguineus is the most widespread tick in the world and a vector of many pathogens infecting dogs and humans. To date, there have been no investigations on the biology of R. sanguineus under natural Mediterranean climatic conditions. Methods. The biology of R. sanguineus was studied under laboratory and natural climatic conditions in southern Italy. Several biological parameters were compared in different seasons, and their correlation with climatic data was assessed. Results. The life cycle of R. sanguineus lasted for a mean of 101·4 and 116·2 days under laboratory and environmental conditions respectively. Reproductive parameters of wild-collected females kept in the environment in May were significantly different from first-generation females maintained in September–October, and the correlation between reproductive parameters and climate data varied according to season. Conclusion. These results indicate that the Mediterranean climate affects the biology of R. sanguineus, which compensates its losses during the initial phases of its cycle in spring with high feeding and moulting rates of larvae and nymphs during summer as well as with high egg production during autumn. These results advance our knowledge of the biology of R. sanguineus and will be useful for the understanding of the eco-epidemiology of tick-borne diseases that this tick transmits.

Several experiments were conducted with Rhipicephalus sanguineus, Dermacentor variabilis and Amblyomma maculatum during which degrees of resistance by rabbits to infestation were quantified. Manifestations of resistance were measured through estimations of “Decreased Tick-Weight Index”, “Decreased Engorgement Period Index” and “Reject Index”. Degree of resistance was evaluated through estimation of Tick Resistance Index. The degree of resistance of rabbits to infestation with each of the three tick species was found to increase with the number of reinfestations. Fully engorged ticks induce the same degree of resistance as partially engorged ones. Nymphal ticks induced higher resistance than larvae, but the resistance conferred by both immature stages was lower than that conferred by adults; previous exposure of rabbits to adults enhanced the degree of resistance against subsequent nymphal or larval infestation. There was cross-resistance between A. maculatum, D. variabilis and R. sanguineus. Resistance induced in rabbits waned with time; rabbits became non-resistant to ticks 12 weeks after the last infestation. Resistance to tick infestation was transferred to rabbits through passive transference of serum from resistant animals. The importance of these observations to the epidemiology of field infestation of animals with ticks is discussed.

Populations of Rhipicephtdus sanguineus, Dermacentor variabilis and Amblyomma maculatum with high and low oviposition capacities were successfully bred in the laboratory. Mating of male and female ticks which possess high oviposition capacity produced female progenies with high oviposition capacity; male and female ticks which possess low oviposition capacity produced female progenies which possess low oviposition capacity. Crossmatings of males with females of opposite oviposition capacity produced female progenies which acquired the category of oviposition capacity of the males in predominant numbers after fourth and fifth generations. It is suggested that the genetic factor for high or low oviposition capacity is either possessed by male ticks alone or is stronger and dominant in the male over that of the female. This genetic factor is also potentiated by successive crossmatings of males and females possessing opposite oviposition capacities.

The possible application of these results to tick control through the suppression of natural population by field release of laboratory-bred populations of male ticks which possess low oviposition capacity is discussed.