Body normally pyriform, occasionally subcircular or elliptical with the posterior end constricted and protruding. In cross section the body is flattened ventrally and convex dorsally. The adult female, and third-instar female (if present) occur inside a hardened test formed by the adult female. Pieces of the second instar may be incorporated in the test. Most writers suggest that the adult female occurs inside the shed skin of the second instar, but according to Kohler (1987) this is not true. Females remain inside the second instar, produce a test, and the second instar skin ruptures and disintegrates. White wax is not common in most species, but filamentous strands are occasionally present laterally. Specimens usually occur on the leaves of the host and are generally dark brown or black.
Halimococcids are most commonly collected on the leaves of palms but also occur on Pandanus.
Palm scales probably have 3 female instars and 5 male instars. Stickney (1934) described several third instar females, but these may be the partially disintegrated venter of the second instar (Kohler 1987). All species occur within a hardened test and as far as is known, produce eggs. Crawlers escape from the test through the anal operculum which is pushed outward. After shedding to the second instar the derm begins to harden, and become sclerotized. The adult female remains within the shed skin of the second instar and produces a wax test similar to the scale cover of armored scales. The test material eventually causes the second-instar exuviae to rupture on the ventral surface and the cover is primarily made up of waxy material produced by the adult. Development of the adult male through the prepupal and pupal stages occurs within the shed skin of the second instar; no wax test is produced. Kohler suggests that there are multiple generations per year and that the fecundity of individual females may be as low as only 10 eggs.