Birds have a tremendous variety of combinations of feather components. For instance the Crowned Crane crest feathers are each made up of a short quill, a twisted rachis, and few barbs. Fly tiers somewhat incorrectly refer to this part of the feather as being the web or webby portion of the feather.
Web is a term synonymous with the whole vane.
Some feathers have barbules without barbicels. Examples would include peacock upper tail covert feather barbs below the eye as well as down feathers from any bird. The barbules also are confusingly referred to as herl for example where the fly pattern for a Quill Gordon calls for a quill body that requires the removal of the herl from the barb. Just as a barb does not necessarily have barbules, barbules do not necessarily have barbicels. Global Fly Fisher .