a few things can cause females to lay infertile eggs. 1. to high basking temps (make sure you know exactly what their basking temps are for your species). 2. to heavy of feedings (as much as they'll eat daily is perfectly fine for juvi's up to around 1-1.5yrs old, after that I cut back to every other day feedings and reduce the numbers). 3. is just the fact a female see's a male can cause egg production (if you have no males around, this won't be a problem). 4. is just the fact she's a female (some females just want to produce eggs). I 100% of the time have a egg laying bin in my female's enclosures once they are a year to year and a half old. If they are producing eggs (fertile or not) you'll notice some of their normal habits change. They'll stop eating, and continue gaining weight. (get a postal scale and measure /monitor weight weekly) They'll start venturing towards the bottom of their enclosure.