Adult Titanus giganteus reach about 16.7 centimetres of body length, the largest confirmed figure for any beetle when horns are excluded. Adults are collected regularly at mercury-vapour lights in French Guiana and neighbouring countries, and the species supports a small ecotourism trade there.
The larva is another matter. No wild titan beetle larva has been documented, and its habits are reconstructed from close relatives and from large tunnels in decaying wood attributed to it. Estimates of larval length, sometimes quoted around 20 to 30 centimetres, rest on those attributed borings rather than on a measured specimen, so they should be treated as provisional.
Adults appear not to feed. Their mandibles are powerful enough to be described as able to snap a wooden pencil, but they are used defensively, and the beetles seem to live on reserves accumulated during a long larval stage of unknown duration.