How Many Ants Do I need? Generally adult horned lizards will eat around 20 to 60 ants per day. You may be able to supplement your lizard's diet with baby crickets and other insects and if so you won't need as many ants. Juveniles will need less ants. Not all Horned Lizards Eat Harvester Ants To the best of our knowledge there are 14 species of Horned Lizards in North America. Most of these depend on Harvester Ants as their staple diet. If your Lizard comes from a cold, high altitude climate (for example Wyoming, Colorado, or Utah high country) or if your lizard is young, it may not eat Harvester Ants.