Basic Guidelines For English Spellings
READ THESE ARTICLES
A psyllid bug of European origin, Cacopsylla (or Psylla) pyricola, a major pest of pear trees which it damages in several ways, especially by feeding on sap and producing excessive honeydew which encourages the growth of certain moulds.
Late 19th century; earliest use found in Eleanor Anne Ormerod (1828–1901), economic entomologist.