This group has been fairly consistently placed in a steingeliine family group taxon. There is considerable variation in characters such as the number of setae on the legs, but the 2 included genera seem to form a distinct group. Steingeliidae Morrison was first treated as a family by Koteja (1989b).
Steingelia is recorded from the Palaearctic and northern Nearctic, and Stomacoccus is known from the Nearctic only.
Steingelia is probably restricted to Betula and Stomacoccus feeds on Platanus.
Stomacoccus platani Ferris has at least 3 instars in the female and there are 5 in the male. Adults overwinter on the bark and migrate to the leaves in the spring. There are as many as 9 generations a year. Steingelia gorodetskia Nassonov has 4 instars in the female and 5 in the male. Most feeding occurs in the second and third instarcysts which are located on main roots underground or deep in bark cracks. Adult females emerge from the third-instar female and move onto the trunks of trees. After mating, adult females produce an ovisac and lay eggs. Crawlers move back to the main roots. There is 1 generation per year.