I took every occurrence of a binomial scientific name in every English-language book indexed by Google in their ngram data:
- 65.8% of occurrences in books of binomial names have the genus (first word) found in Wiktionary
(23821553 of 36164803; Wiktionary data: 2015-11-20. 248 genera entries needed to reach 75%)
- 73.7% of occurrences in books of binomial names have their epithet (second word) found in Wiktionary.
[26680536 / 36164803; Wiktionary data: 2015-11-20; Ngram data: 2012. Probably an underestimate as it's missing a lot of the long tail; that is, any scientific names used less than 40 times (ever) are excluded due to how Google's ngram data is stored, and therefore only 52,625 of the millions of binomials in the Catalogue of Life are included. The Catalogue of Life (2014) was used to define what is and isn't a species. A Latin or translingual entry was required for an entry to count as existing.]
- 25.7% of occurrences in books of binomial names are found in Witkionary (as a two-word binomial entry)
(9310553 of 36164803; Wiktionary data: 2015-01-02; 30 to reach 30%)
Additional epithet entries needed in Wiktionary...
- to reach 75%:
199 entries (list)
- to reach 80%:
242218 entries (list)
- to reach 85%: 792 entries
- to reach 90%: 1920 entries
- to reach 95%: 4492 entries
- to reach 99%: 10620 entries
- to reach 100%: 14575 entries (100% of those commonly found in books)
- Of the genera found in books: 19.7% have entries.
(3308 / 16767). 2015-11-20. 151 added since 2015-01-02
- Of the specific epithets found in books: 32.6% have entries.
(7034 of 21529; the ones that appear in a scientific name which appears at least 40 times in books. Wiktionary: 2015-11-20. 89 added since 2015-01-02, or 0.41 p.p.)
- Of the 52,625 binomials commonly seen in books, 4.9% (2590) have entries. Wiktionary: 2015-11-20. 144 added since 2015-01-02.
I am Pengo on en.wikipedia.