The Collaborative International Dictionary of English v.0.48:

Spittle \Spit"tle\, n. [From Spit to eject from the mouth: cf.
   Spattle, and AS. sp[=a]tl.]
   The thick, moist matter which is secreted by the salivary
   glands; saliva; spit.
   [1913 Webster]

   Spittle insect. (Zool.) See Cuckoo spit
   (b), under Cuckoo.
       [1913 Webster]

WordNet (r) 3.0 (2006):

spittle insect
    n 1: small leaping herbivorous insect that lives in a mass of
         protective froth which it and its larvae secrete [syn:
         spittle insect, spittlebug]