Ala(Pl. Alae)

Thin cuticular projection or fin,or thickened wings of Cuticle,running longitudinally, usually lateral or sublateral on the body,frequently paired and Narrow or Broad.Cervical,Caudal or Lateral types exist

-Cervical Alae confined to anterior end

One in e.g. Toxocara canis ,Three in e.g. Physocephalus sexalatus

-Caudal Alae: They are seen on the posterior end of only the Male sex. e.g.  Abbreviata paradoxa

Sometimes its so developed and forms a Copulatory bursa.  e.g. Haemonchus longistipes

-Lateral Alae:They are found in both sexes and extend along the length of the body overlying the lateral field.  e.g. Paraorientatractis semiannulata (Cosmocercoidea)