How do you tell male scorpions from female scorpions?
First of all, it is usually only possible to determine the sex of adult scorpions. Juveniles generally look the same for both sexes. Subadults of both sexes usually look like females. Adult males and females can vary in a number of characters. Sometimes the most obvious is the general difference in body shape and size. Males tend to be smaller and thinner, with relatively longer metasoma and pedipalps than females of the same species. Often there is some allometric growth in the pedipalps of the males so that they are larger, longer, or thicker than those of the female. You can see some of these differences in the picture below.
The PECTENS of males are usually longer than those of the female and bear larger and more PECTINAL TEETH. In the example figures below, you can see that the PECTEN of the male is longer than that of the female. The tip of the PECTEN goes beyond the distal end of COXA IV (green arrow). The tip of the female PECTEN, however, does not reach the distal end of COXA IV. Furthermore, each PECTINAL TOOTH on the male PECTEN is larger (relatively) than the PECTINAL TEETH on the female PECTEN.
Males of many species have a pair of genital papillae that protrude from beneath the GENITAL OPERCULA. In some species there are additional differences between the sexes in the GENITAL OPERCULUM and BASAL PIECE.