What are the symmetry-in-pair symbols usually appear in Wingdings fonts?
A fleuron is a typographic element, or glyph, used either as a punctuation mark or as an ornament for typographic compositions. Fleurons are stylized forms of flowers or leaves. Robert Bringhurst in The Elements of Typographic Style calls the forms "horticultural dingbats." It is also known as a printers' flower, or more formally as an aldus leaf hedera leaf, or simply hedera (ivy leaf) symbol.
There are names assigned to all Wingdings symbols, here are the ones you've highlighted (one from each set for the sake of brevity):
They are included in the Ornamental Dingbats Unicode block (PDF) and described slightly differently there.