Here are my theories for Wings of Fire.
HiveWings have several books about Pyrrhia, but they are apparently "forbidden"[]
According to what might be true, HiveWings are descendants of Clearsight and Sunstreak. Sunstreak seemed to be interested about Pyrrhia. Maybe, just maybe, Clearsight would have told her newfound tribe about Pyrrhia, and dragons might have written about it.
HiveWings, however, might have hidden these books away from the SilkWings so that they wouldn't get any ideas on rebelling based on what happened in Pyrrhia (Example: getting a new queen).
Lady Scarab is Cricket's Astronomy teacher (and her favorite teacher)[]
Cricket and Blue were engaged in a conversation about Lady Scarab, and Cricket agrees to Blue describing her as "fiercely not awful". Also, Lady Scarab is mentioned to own a telescope, which makes sense for her to teach astronomy.
Then why is she a Lady, and have a royal title? Well, she might be another sister to the queen, who had a obsession with space. She might have rejected an offer of having a Hive, and instead persuaded her dream to study astronomy.