1a. Key to females. - Abdomen with 4 free segments, first abdominal segment (genital) usually longer (or wider) than the next segment of abdomen. P5 absent (when present in few species, vestigial).

1b. Key to males. - Abdomen with 5 free segments, first segment usually shorter than the next one, fifth one sharply reduced. P5 always present, well developed.