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Summary
The ratio between bisexuality and parthenogenesis in 8 different populations of the Embiid Haploembia solieri Ramb, has been analysed.
The results showed that some populations are pure amphigonical, some others pure parthenogenctical, while others have different degrees of promiscuity.
The samples have been used also for determination of percentage of Diplocystis infection.
Based on experimental data, already established, the author considers the sterility in the male sex, produced by the Gregarine, as the primitive cause determining the accidental parthenogenesis which seems to be the first step in the evolution to the constant parthenogenesis arising in some localities of the amphigonical distribution area.
The theory of an ancient origin of the actual geografical parthenogenesis which regards it as a tertiary relict of the Tyrrhenis is therefore abandoned.