Striped Orbs Seen in Pure Water Drops

Besides photographing many striped orbs floating about in dry air (indoors and outdoors), as shown here,  I also sometimes photograph striped orbs in water drops. Below is a composite of photos I have taken showing striped orbs (open the photo in a separate browser window  to see it at higher resolution). These photos were all taken while photographing ordinary drops of pure, clean water falling against a dark background. Why these stripes appear is a total mystery to me.