Anatomy of the wing of a butterfly Blue: costal nervure; teal: subcostal nervure; purple: subcostal nervules; green: discoidal nervules; light blue: median nervules; yellow: submedian nervure; brown: internal nervure; pink: interno-median nervule; red: median nervure; orange: disco-cellular nervules.
Francis Jeffrey Bell
Comparative Anatomy, published in Philadelphia by Lea Brothers &amp; Co., 1885, page 378: <a rel="nofollow" class="external free" href="https://books.google.com/books?id=SrQVAAAAYAAJ&amp;dq=butterfly%20wing%20anatomy&amp;pg=PA378">https://books.google.com/books?id=SrQVAAAAYAAJ&amp;dq=butterfly%20wing%20anatomy&amp;pg=PA378</a>