Life cycle of the camel tick Hyalomma dromedarii (Acari: Ixodidae) under field conditions in Northern Sudan.

Abstract

Engorged Hyalomma dromedarii females were placed for development in shade and sun (open non-shaded site) in April, August and December for two successive years. Engorged nymphs were also placed at the same sites in January, March, May, June, July and August. Preoviposition periods ranged between 9.8 and 11.7 days in the shade but longer in the sun in December (14.7 days). Egg production index was higher in August (0.72) than in April and December (0.46 and 0.39, respectively) in shade and in August compared to December in the sun (0.65 and 0.29, respectively). In shade and in sun, the prehatching periods were longer in December (50.7 and 48.2 days) than in April and August (25.6 and 29.0 days). Percentage hatchability ranged between 82 to 94.1% and 56.2 and 58.9% in the shade and sun, respectively. Number of eggs laid and eggs hatched were positively correlated with females' engorgement weights. There were high mortality rates of females in the sun and most of the eggs desiccated. Slight increased ambient and soil temperatures increased egg production, shortened preoviposition periods and decreased hatchability while increased humidity shortened preoviposition and prehatching periods and increased hatchability. Nymphal-adult moulting periods were long in January (20.7 days in the shade and 14.4 days in the sun) and short in August in the shade (7.8 days) while they were only 6 days in May and June in the sun. High numbers moulted in all months in the shade (ranges 23.3-29.5 nymphs). The mean mortality of engorged nymphs in the shade was very low. However, in the sun mortality was high (12.9-30 nymphs). Premoulting periods were negatively correlated with ambient temperature but positively correlated with humidity. In the shade, mean number of nymphs moulting increased with increased mean ambient temperature, humidity and rainfall.