When it is hot I like wearing skirts on my hybrid bike. I wear regular bike shorts underneath. I then discovered that it is nice have shorts under skirts for for just knocking around. So, I bought some compression running shorts (which have no padding) and a pair of tri shorts (which have basically some fleece in lieu of padding) and I wear them sans underwear with my skirts. Very comfy plus if I want to hope on a bike for a short ride they are nice for that too. Bike shorts have given me an aversion for underwear.