To protect eggs and caterpillars from desiccation, it is important that the wine cooler temperature be set at around 45°Fwith a humidity set between 60 and 90 percent.  Below 60 percent creates possible desiccation and above 90 percent creates concerns with mold.  Whenever overwintering butterflies in any stage, you want to avoid these bookends.  (These numbers are approximate depending upon temperature and humidity of the external environment.)