*[id^="widget-"] > div.widget-top > div.widget-title > h4:before
This uses the attribute prefix selector from CSS3.
If it also must end with _yikes_mc_widget-__i__
then:
*[id^="widget-"][id$="_yikes_mc_widget-__i__"] > div.widget-top > div.widget-title > h4:before
Or, if you can get away with just selecting something that has yikes_mc_widget
in the middle:
*[id*="_yikes_mc_widget"] > div.widget-top > div.widget-title > h4:before