Relationship between Primary and Tertiary Sex Ratio in the Two-Spotted Spider Mite (Acarina: Tetranychidae)

Abstract

Relationships between primary sex ratio (number of female eggs/number of male eggs) and tertiary sex ratio (number of adult female offspring/number of adult male offspring) were investigated in four environmental regimes: good and poor environments for parental development × good and poor environments for oviposition and offspring development (poor environments were damaged leaves upon which mites had previously fed). High and significant correlations between the two sex ratios were found in all environments. Within each environmental subclass, death rate of male offspring is higher than that of female offspring. As a result, the primary sex ratio is adjusted upward in each case. The sizes of the adjustments are negligible when the environment for offspring development is good, but are appreciable when the environment is poor. The quality of environment for parental development had no apparent effect on sex ratio adjustment.