The free downloaded contents pages are in pdf format (about 100KB each).
Tip. If you RIGHT click any download and Save Target As... you will keep a copy on your own computer which you can read at leisure. It also usually works as an alternative when Acrobat fails to open the file directly with a LEFT click.
Contents Pages of Individual Chapters
Ch. 4.0 Pieridae Introduction (contains essential introductory material for chapters 4.1 to 4.8), 8 pages, download
Ch. 4.1, Large and Small White Group, 57 pages, download
Ch. 4.2, Green-veined White Group, 43 pages, download