That too is incorrect, and for the following reasons:
Ants are extremely small and live extremely short life spans. They do not grow much beyond their larval form, and die within a matter of days.
Ants need to eat very little simply because their size and lifespan are so short that they do not require the nutrients for a prolonged period of survival. This is also why they never sleep: once their energy is expended, they die. There is no recharging.
However, xenomorphs are much larger and more complex creatures. The bigger the animal, the more nutrients it requires, plain and simple. Being bigger means more energy must be expended to move and to function, and the energy necessary for such actions scales appropriately with the amount of food required to survive. Having additional limbs, such as a tail, and sharper senses and an advanced nervous system, as xenos do, greatly adds to this toll.
It is also very obvious that xenos are capable of some sort of stasis or hibernation. How long this lasts, however, cannoy be determined. They could do it for months, like mammals, or decades, like Water Bears.