bug names -- or the fly that's not a fly: a griceian re-analysis

From World Wide Words,

"As a professional entomologist, I enjoyed your bit about insect common names."

"As an aid to my students over the last 35 years, I have informed them of
the rule you explain."

"Your piece also illustrates the hazards of common names divorced from the relevant scientific names."

"In my experience, a 'June bug' and 'tumblebug' are beetles and 'greenfly'
is a 'bug'."

"'Blackfly' is more interesting, since it can be used
for a true fly and also for an aphid/'bug' - its usage would be
clarified if the rule were followed in this case - 'black fly' for
the true biting fly, and 'blackfly' for the aphid."

But it's not.

-- Speranza, Bordighera