Hello
This thing happens at ant queens, which are very good feeded by proteins

Ovularia gets bigger and she will produce more laying than other queens, without this thing but still in her age, so don´t worry(,be happy

) about fat(insects can get fat, as others said)

It´s very interesting thing, because it happened at few of my queens and than they wasn´t feeded, she got this thing and than I was wondering why she´s so full, when I wasn´t feeding her colony last time

I knew also a name for this, but I failt it sry