Ephemerida refers to a family of mayflies (also called shadfly) that have very short lives. The adult lifespan ranges from 30 minutes to 1 day, and their primary function is procreation.
Sharon Acker, who plays Lavinia Sedgewick, would show up on TV again three months later in episode The Mark of Gideon (1969), in which she played Odona, of the planet Gideon. But in this case she had the opposite problem, as the people of Gideon had eliminated all diseases and other causes of death, allowing them to live virtually forever.
The Dodge City street set from the CBS western Gunsmoke (1955) makes one of its many appearances as a town by a different name and invariably a point of interest for James West. This time the Dodge set stands in as the town of Sedgewick with the Dodge hotel set redressed as the Sedgewick Spa.
All of the commercial break stillframes are close-up of actors faces.
Granted, the mayfly's sexually mature adult stage is very brief; the immature water nymph stage, however, can last several years. Consider, the ultimate insect example of 'life is short' outlives all insects but the 17 year locust.