Lampyris noctiluca - are a Brazilian species of
"firebug" popularly named "vagalume" ("wandering light) which
is distinct from another kind - "pirilampo" or "fire lamp"
- which belong to the "Elaperidae"( a kind of jumping beetle
that sometimes has no "bioluminiscence").
The
enzyme that produces the Lampyris light is named "luciferase". (
information gleaned from internet sources)
"Pale Fire" is often mentioned along the novel as
referring to "borrowing light from someone else's own" ( like the
moon's surface shines by reflecting the light of the sun ).
Firebugs have their own luminescence and would
not qualify as "arrant thieves"...