In solifugids of the family Ammotrechidae, the anterior margin of the propeltidium (the part of the head that bears the two eyes)  slopes backwards evenly from the eye tubercle, and a translucent husk-like flagellum is present on the mesal face of the fixed cheliceral finger in males (Figure 1).   In members of the family Eremobatidae (the only other family of solifugids found in California), the anterior margin of the propeltidium forms a straight line perpendicular to the longitudinal axis of the body, and no husk-like flagellum is found on the chelicera of males.

Two genera of ammotrechids occur in California: Branchia Muma 1951, and Ammotrechula Roewer 1934.   Males of both genera are easily distinguished by the form of the flagellum.   Males of the genus Ammotrechula have a tear-drop shaped flagellum with strongly incurved margins (Figure 2).   Males of the genus Branchia have a cleaver-shaped flagellum (Figure 3).

Figure 2.  Flagellum of male Ammotrechula sp.                               ©Warren E. Savary, 2003

Figure 3.  Flagellum of male Branchia sp.                                          ©Warren E. Savary, 2003