Sizes and developmental viability of sequentially oviposited eggs of dog ticks: Rhipicephalus sanguineus and...

Sizes and developmental viability of sequentially oviposited eggs of up to 12th day oviposition by dog ticks Rhipicephalus sanguineus and Haemaphysalis leachi leachi were studied. The mean length and breadth of eggs oviposited on days 1 and 2 were greater (0.45 +/- 0.111 and 0.44 +/- 0.042) than those of subsequent ovipositions. The eclosion periods of eggs laid from 7th to 12th day of oviposition were progressively shorter (17, 16, 14 and 19, 17, 0 days) than those of eggs laid on days 1 and 2 (20 and 22 days) by R. sanguineus and H. leachi leachi, respectively. The percentage mortality of eggs of days 11 and 12 oviposition (70.3% and 100%) was significantly higher than that of earlier ovipositions (9.6% and 31.7%) for R. sanguineus and H. leachi leachi, respectively. The numbers of larvae which engorged on rabbits after hatching from eggs of 11th and 12th day oviposition (43 and 0) were significantly fewer than those which hatched from eggs of days 1 and 2 (79 and 63) for R. sanguineus and H. leachi leachi, respectively. A total of 383 larvae of R. sanguineus engorged on rabbits compared to 225 larvae of H. leachi leachi. It is concluded that eggs of early ovipositions of R. sanguineus and H. leachi leachi are longer and wider and more viable than those laid later in the oviposition cycle. The significance of these findings in terms of hatchability of eggs is discussed.