Female: Extra cuticular layer always present, generally loose, never membranous. Labial annuli two (exceptionally three) not modified or separated (except H. hesperis and H. truncata). Vulva a transverse slit over half of body diameter long. Vagina straight or curved but not sigmoid.

 Male: Labial region marked by a discontinuity in body annulation, usually offset; labial framework in lateral view appearing as “spectacle mark.” Spicules arcuate, semi- circular, U- or hook-shaped. Lips of cloaca forming a penial tube bearing a single hypoptygma at its tip. Caudal alae covering less than one-third of the tail. Tail longer than that of female.

 Juvenile: Fourth-stage male juvenile without stylet.