Oviposition of the American Dog Tick (Acarina: Ixodidae)

Abstract

Female American dog ticks, Dermacentor variabilis (Say), were engorged on bovines and were held at 27°C and > 80% relative humidity under a photocycle of 12 hours light: 12 hours dark. The average weight (0.398 g), length of preoviposition period (5.3 days), and number of eggs laid per female (3276.8) did not differ significantly for groups of females disturbed daily by removal of eggs and groups of females allowed to oviposit undisturbed. The weight of a newly laid egg averaged 77 µg; the average weight of an egg weighed after oviposition ceased but before hatch began averaged 66 µg. With all females, the number of eggs per female was highly significantly correlated with the weight of the female. With undisturbed females, the length of the preoviposition period was negatively correlated with weight; this was not true of the disturbed females. The Index of Reproduction Efficiency (number of eggs per weight of female) and the Index of Conversion Efficiency (weight of eggs per weight of female) were correlated with the weight of the undisturbed females but not the disturbed females. Peak daily oviposition, an average 381.5 eggs per female, occurred on the 3rd day of oviposition. An average > 300 eggs per female was laid on days 2–5; thereafter the rate of oviposition gradually declined. The length of the oviposition period (average 20 days) was highly significantly correlated with the weight of the female and with the number of eggs laid. The average minimum incubation period was 20 days.