Impact of humidity on clustered tick eggs.

Eclosion of larvae from clustered tick eggs (1, 5, 10, 15, 20, 25, 50, and ±1,000 eggs) of Rhipicephalus sanguineus (Rs), Rhipicephalus microplus (Rm), Amblyomma cajennense (Ac), and Dermacentor nitens (Dn) was investigated at 43, 75, and > 98% relative humidity (RH) and 25 °C. Susceptibility of eggs to dehydration varied among tick species (Rs < Rm < Ac and Dn) and the number of clustered eggs but even singularized eggs of all tested species matured, and larvae eclosed at RH > 98%. A minimum of 25 clustered eggs and relative humidity close to saturation is suggested for quantitative tests on ovicidal activity of acaricides for related tick species.