Key to the genera of Macrobiotidae

1. Claws on the fourth pair of legs reduced to granular rudiments or absent; claws on the first three pairs of legs of the Xerobiotus type (Fig. 20 E) ............................................................................................................ Pseudohexapodibius

- Claws on the fourth pair of legs normally developed.................................................................................................. 2

2. Bucco-pharyngeal apparatus with rigid tube ................................................................................................................ 3

- Bucco-pharyngeal apparatus with the tube subdivided into an anterior rigid and a flexible caudal tract .................. 11

3. Claws of the hufelandi type (Figs. 1 F, 20C); peribuccal lamellae may be present or absent ....................................... 4

- Claws different; peribuccal lamellae present................................................................................................................ 9

4. Dorsal wall of the buccal tube smooth (without ridge or hook). Branches of the stylet furcae typically shaped (Fig. 4 A), i. e., with thickened, swollen, rounded apices ...................................................................................................... 5

- Dorsal wall of the buccal tube with a dorsal ridge or hook. Branches of the stylet furcae with thickened but not swol- len apices (Fig. 4 B) ....................................................................................................................................................... 8

5. Double systems of transverse ridges present in the buccal armature (Fig. 21 B)..................................... Famelobiotus

- Only one (well or less developed) system of dorsal and ventral transverse ridges present in the buccal armature..... 6

6. Peribuccal lamellae absent. Peribuccal papulae present. Buccal tube narrow or very narrow; stylet supports inserted on the bucal tube at 48–73 % of its length in the known species (Fig. 22 C, D)........................................... Minibiotus

- Peribuccal lamellae present. Stylet supports inserted on the buccal tube at well over half its length (Fig. 21 A) ........ 7

7. All the following characters present: claws of the hufelandi type; cuticle without pores; buccal tube wide; three rod- shaped macroplacoids; microplacoid distant from the third macroplacoid (more than its length) (Fig. 21 C); eggs with conical processes and areolated egg shell .......................................................................................... Paramacrobiotu s

- Claws of the hufelandi type. At least one of the above indicated characters is different; in particular, when three macroplacoids and microplacoid are present, the microplacoid is not so distant from the third macroplacoid (Fig. 21 A) ........................................................................................................................................................... Macrobiotus

8. Dorsal wall of the buccal tube and anterior tract of the ventral lamina with a ridge but without a hook (Fig. 22 A)..... ................................................................................................................................................................... Adorybiotus

- Both buccal tube dorsal wall and anterior tract of the ventral lamina with a hook (Fig. 22 B) ..................... Richtersius

9. Claws of the Xerobiotus type (Fig. 20 E) ....................................................................................................... Xerobiotus

- Claws of the Calcarobiotus type, at least on the first three pairs of legs (Fig. 20 A,B) ............................................. 10

10. Claws of the Calcarobiotus type with very long accessory points connected to the primary branch by a flexible tract (Fig. 20 B) ...................................................................................................................................................... Schusterius

- Accessory points normally developed (Fig. 20 A) ................................................................................... Calcarobiotus (see below the key to the subgenera)

11. Claws of the Biserovus type (Fig. 20 F). Peribuccal lamellae present (Fig. 23 A).......................................... Biserovus

- Claws of the hufelandi type (Figs. 1 F, 20C). Peribuccal lamellae present or absent.................................................. 12

12. Peribuccal lamellae absent, peribuccal papulae present (Fig. 23 B). Branches of the stylet furcae typically shaped (Fig. 23 B) ....................................................................................................................................................... Minilentus

- Peribuccal lamellae present (Fig. 23 C). Branches of the stylet furcae arched and converging backwards (Figs. 4 C, 23C)............................................................................................................................................................. Insuetifurca