He insists that specifically a mayfly, which does walk on only four of its legs, only ever using the other two to grip during mating, only has four legs, while discussing the locomotion of walking. Which seems fair. If legs are for walking, mayfly do only have four legs.
It is also there he insists that flies have four legs.
(Yes, there is a particular insect from his area that seemingly only has four legs -- but it is still daft.)