1) Ephemera 2) Insect 
In computer science, finalization occurs when a garbage collector (GC) informs an application that an object is `almost collectable.` It is used to help an application maintain its invariants. Weak references may be used by a garbage collector to determine the objects that are almost collectable. However, weak references are not sufficient to de.....
creature that lives for only one dayinsect that lives for only one day
• (n.) One of the ephemeral flies.
E·phem'e·ron noun ; plural Ephemera . [ New Latin See Ephemera .] (Zoology) One of the ephemeral flies. 
ephemeral noun anything short-lived, as an insect that lives only for a day in its winged form
anything short-lived or ephemeral. · items designed to be useful or important for only a short time, esp. pamphlets, notices, tickets, etc.