Lutago fetosus combined a very small body with the compact abdominal construction of a flight-capable weevil. Its front coxae touched at the midline, the first two abdominal segments were greatly enlarged, and the hindbody was relatively broad rather than elongate. Hindwings are present in the genus, showing that these tiny adults were not permanently flightless.

Nothing in the fossils identifies a host plant. The form of the beetle and its place among the diverse London Clay curculionids make phytophagy secure at a broad level, while an association with woody vegetation is plausible from the ecology of comparable weevils in the assemblage rather than direct evidence. Most specimens preserve the pyritised hindbody, so the abdomen, coxae and elytral sculpture are much better known than the head.