It won't hurt for your HL's to go a day without eating. Just try not to let it happen often. At times when I run out of ants, I keep a container of mealworms for a treat. Just a few every now and then.
A horned lizard will "drag" his belly from "time to time". But the critical question is; is his belly dragging "all the time" due to an unhealthy reason? Such as exreme overweight? Normally this is not a problem at all with most beginners. They're usually underfeed. If you feed your HL harvester ants all the time then you probably have nothing to worry about. But excessive crickets and mealworms are really high in fat, chitin, and bad in calcium/phosphorus ratio. Too much of the wrong thing can kill him. Especially for a captive HL in a small space who gets no exercise. Your talking to a guy who kept a HL on mainly crickets and mealworms for 3 years. But that sort of thing can be dangerous. They are designed to eat harvester ants ( most are ) primarily. And they will do much better and probaly live longer if they have them. Just use common sense about it. If it looks way out of shape with what you see in other examples of HL's, then it's probably not good.
-----
"A man that should call everything by it's right name, would hardly pass the streets without being knocked down as a common enemy." The Complete Works of George Savile, First Marquess of Halifax 1912,246
