Source : Webster's Revised Unabridged Dictionary (1913)

Psylla \Psyl"la\, n.; pl. {Psyll[ae]}. [NL., from Gr. ? a flea.]
   (Zo["o]l.)
   Any leaping plant louse of the genus {Psylla}, or family
   {Psyllid[ae]}.

Source : WordNet®

psylla
     n : small active cicada-like insect with hind legs adapted for
         leaping; feeds on plant juices [syn: {jumping plant louse},
          {psyllid}]