My white butterfly have spawned no less than 12 times in a row, he greedily eating every egg the minute she released it. The last two spawns he actually fertilized and they guarded them twice.....then ate them. My butterflies are only a year or so old, very young yet, I understand with some of them it takes time, could be around age 18 months - 24 months before they get it right. On the other hand I have a pair that got it right the first time and had wrigglers. Just be patient. After 2 days you should be able to at least tell if they are fertile, you'll see that they stay transparent and you can see a little speck that will be eyes. If you see that, at least they are a fertile pair, so it's a waiting game.