Hi maybe I can help you, know one is answering my questions either. I only have experence with the Desert HL and the Round tail HL for 3 years. It sounds to me that maybe you have to small of a cage or the ants are to large. There has to be enough room in your cage for the lizard to be in the cage without ants crawling all over the lizard, and onless the cage is really large you should just put in a few ants, and wait tell they are eaten, unless you are sure he will eat 6 or 7 at a feeding. I have never had the short horn, but I think it needs at least a 10 or 15 gal. aquarim just for 1 or 2 babies, if those lizards were larger you would need a 20 gal. aquarim. I know i spelled that wrong but you know what I mean. What size of cage do you have? Also the baby HL's eat smaller ants then the adults.
Well I hope this helps. Good Luck