From the "Index of Personal Names" I have created a 'total number of referrals' index value by adding up all the weighted referrals (i.e., regular font=1, bold font=2, bold & underlined=3) reported for particular individuals. (Thus, a person mentioned in four Wallace works, represented in the item list with two items in bold font and two in bold + underlined, produces an index value of 2+2+3+3=10.) In other words, the numbers reported below are statistics, not the actual total number of referrals; I believe the system used here is more fairly reflective of the relative attention given each person overall in Wallace's writings because it doesn't put undue weight on long works that contain a very large number of mentions of a particular person. The following individuals scored a '20' or higher on this scale, ranked in order.

318----Darwin, Charles [English naturalist 1809-1882]. This total clearly indicates what a tremendous debt Wallace's work owed to Darwin, whether Wallace agreed with him all the time or not.
 
108----Spencer, Herbert [English philosopher and sociologist 1820-1903]. Wallace had genuine admiration for Spencer's abilities as a thinker, though later on in their careers he came to feel that Spencer had lost his direction.
 
86----Bates, Henry Walter [English entomologist 1825-1892]. Wallace's friend Bates, best known for his contributions to the study of protective mimicry, introduced Wallace to the joys of insect collecting and later accompanied him to the Amazon.
 
81----Lyell, Charles [English geologist 1797-1875]. Lyell's views on the conservative and gradual nature of environmental change strongly informed Wallace's ideas on process in biology and physical- and bio-geography.
 
75----Huxley, Thomas H. [English biologist and philosopher 1825-1895]. Wallace often cited and quoted Huxley--whose command of his subjects he much respected--but actually made relatively little use of his ideas.
 
61----Carpenter, William B. [English physiologist 1813-1885]. Carpenter's summary dismissal of spiritualism led him to a long spar with Wallace over the subject.
 
47----Hooker, Joseph D. [English botanist 1817-1911]. The writings of Hooker, pre-eminent botanist of his time, furnished Wallace with numerous examples for his ideas, especially when it came to biogeography.
 
45----Galton, Francis [English sociologist 1822-1911]. Galton, whose studies on heredity and a number of other subjects Wallace much admired, was also a founder of the science of eugenics (which Wallace detested).
 
44----Sclater, Philip Lutley [English ornithologist 1829-1913]. Sclater, Secretary of the Zoological Society and editor of the journal Ibis, shared many of Wallace's natural history interests.
 
42----Mill, John Stuart [English economist and philosopher 1806-1873]. Wallace was particularly intrigued by this major figure's ideas on land reform and social economy.
 
42----Weismann, August [German biologist 1834-1914]. Weismann became well known for his important theory of the germ plasm, and in turn as a vocal anti-Neo-Lamarckian.
 
41----Linnæus [Swedish botanist 1707-1778]. Wallace makes reference to Linnæus in no fewer than thirty of his writings.
 
40----Crookes, William [English physicist and chemist 1832-1919]. Crookes, a famous physical scientist, spent a good deal of time attempting to test the phenomena of spiritualism, and Wallace often cited and supported him in that context.
 
39----Lamarck, Jean Baptiste [French naturalist 1744-1829]. Wallace continued to campaign against Lamarckianism--the notion that acquired characters might be inheritable--through to the end of his life.
 
37----Gray, George R. [English zoologist 1808-1872]. Gray, who worked at the British Museum, was often referred to by Wallace in his writings on the systematics of insects and birds.
 
37----Lubbock, John [English financier and naturalist 1834-1913]. Wallace fairly frequently referred to and/or commented on the rather socially conservative Lubbock's researches in anthropology, entomology, and animal behavior.
 
35----Belt, Thomas [English naturalist and writer 1832-1878]. Wallace considered Belt one of the most astute field observers of his time, and often referred to his researches to help him make particular points.
 
34----Spruce, Richard [English botanist 1817-1893]. Spruce collected in the Amazon at the same time Wallace was there, and the two remained friends and in contact until Spruce's death.
 
33----George, Henry [American economist and reformer 1839-1897]. George's efforts on behalf of land reform made him better known (and more influential) on the subject than Wallace, even in England.
 
33----Croll, James [Scottish astronomer and geologist 1821-1890]. Wallace was particularly interested in Croll's attempts to link the onset of glacial periods to periodic astronomical forces.
 
32----Newton, Isaac [English physicist 1642-1727]. The frequency with which Newton's name comes up in Wallace's writings is a bit surprising, though several sources have noted how Wallace treated natural selection as a virtual "law of nature" akin to gravitation.
 
31----Bonaparte, Prince Charles Lucien [French ornithologist 1803-1857]. Bonaparte, the nephew of Napoleon Bonaparte, produced a compilation of the bird species of the world that was Wallace's "constant companion" as he roamed through the wilds of Indonesia.
 
31----Humboldt, Alexander von [German geographer 1769-1859]. Humboldt visited South America about fifty years before Wallace did, setting a high example for all scientist-explorers who followed.
 
30----Agassiz, Louis [Swiss-American naturalist 1807-1873]. Anti-evolutionist Agassiz, especially celebrated for his working out of the theory of continental glaciation, became one of America's best known naturalists.
 
29----Romanes, George J. [English biologist 1848-1894]. A pioneer in studies on the evolution of the mind, Romanes proposed a theory he called "physiological selection" which Wallace would have no part of.
 
28----Allen, Grant [Canadian-English writer and naturalist 1848-1899]. Wallace thought very highly of Allen's literary talents (though not always his ideas), reviewing three of his popular science books in the journal Nature.
 
28----Home, Daniel D. [Scottish spiritualist medium 1833-1886]. Wallace often referred in passing to Home, history's most famous and spectacular medium.
 
28----Owen, Richard [English zoologist and anatomist 1804-1892]. Wallace often cited Owen as an authority when it came to anatomy and morphology, regardless of the fact that Owen never accepted Darwinism.
 
27----Morgan, C. Lloyd [English biologist and psychologist 1852-1936]. Morgan, a college professor at Bristol, is sometimes referred to as the father of comparative psychology.
 
27----Tyndall, John [Irish-English physicist 1820-1893]. Wallace frequently referred to the various researches of this very prominent scientist in passing.
 
27----Mivart, St. George [English zoologist 1827-1900]. Like Wallace, Mivart, though an evolutionist, differed with Darwin on the matter of the evolution of humankind's "higher attributes."
 
26.5----Allen, Charles [Wallace's Malay Archipelago field assistant]. Relatively little is known about Charles Allen, but he was Wallace's field assistant for two periods during his Malay Archipelago expeditions, and became a remembered collector in his own right.
 
26----Newton, Alfred [English ornithologist 1829-1907]. Newton, a professor at Cambridge, was instrumental in steering Wallace in a direction ultimately leading to his publication of The Geographical Distribution of Animals in 1876.
 
25----Owen, Robert Dale [Scottish-American writer and reformer 1801-1877]. Owen carved out a multi-faceted reputation almost equal in sum to that of his father's (Robert Owen).
 
24----Argyll, Duke of [Scottish statesman and writer 1823-1900]. The Duke of Argyll's amateur status as a naturalist did not prevent him from entering into various scientific debates, including that over the origin of species.
 
24----Tylor, Edward B. [English anthropologist 1832-1917]. Tylor, though like Wallace very little schooled formally, became the most prominent anthropologist of his time.
 
23----Ramsay, Andrew C. [Scottish geologist 1814-1891]. Ramsay's theory of the glacial origin of alpine lake basins so interested Wallace that he put considerable effort into strengthening the argument.
 
23----Howitt, William [English historian and writer 1792-1879]. Wallace commented on Howitt's writings in a variety of contexts, ranging from spiritualism and philosophy to travel, economics, and social conditions.
 
22----Blatchford, Robert [English socialist and newspaperman 1851-1943]. Wallace often commented on Blatchford's socialistic ideas, especially via the newspaper Blatchford edited for over thirty-five years, The Clarion.
 
22----Buffon, Comte de [French naturalist 1707-1788]. The proto-evolutionary ideas of this great figure are discussed or mentioned by Wallace in sixteen of his writings.
 
22----Gregory, William [Scottish chemist 1803-1858]. Gregory was one of many prominent scientists in the mid- and late-nineteenth century who considered paranormal subjects; his special interest was mesmerism.
 
22----Günther, Albert C. L. G. [German-English naturalist 1830-1914]. Wallace often used Günther as an authority when he discussed fishes, reptiles, and amphibians, groups with which he was not expertly familiar.
 
21----Cope, Edward Drinker [American paleontologist 1840-1897]. Cope, well known for his work on dinosaurs, was also the leader of the American school of Neo-Lamarckians.
 
21----Westwood, J. O. [English entomologist 1805-1893]. Westwood was one of the more prominent entomologists of his time, and also a superb zoological illustrator.
 
20----Chambers, Robert [Scottish publisher and writer 1802-1871]. Chambers, author of Vestiges of the Natural History of Creation, was also a publishing magnate and, perhaps most interestingly, a spiritualist.
 
20----Herschel, John [English astronomer 1792-1871]. Herschel, one of the founders of the Royal Astronomical Society, was one of the most prominent astronomers of his time.
 
20----Hewitson, William C. [English zoologist and illustrator 1806-1878]. Hewitson not only accumulated one of the largest collections of butterflies of his time, but stood unrivalled as a zoological illustrator.
 
20----Owen, Robert [Welsh utopian socialist 1771-1858]. Considering Wallace's apparent debt to Owen's example, it is somewhat strange that Owen's name appears only once in Wallace's writings before 1891.
 
20----Thomson, William (Lord Kelvin) [Irish-English physicist 1824-1907]. This famous physicist created a dilemma for Darwinists when he calculated (incorrectly, as it turned out) that the Sun had to be no more than one hundred million years old.
 
20----Bellamy, Edward [American socialist author and utopian 1850-1898]. Bellamy is most famous for his utopian novel set in the year 2000, Looking Backward.
 
20----Tennyson, Alfred, Lord [English poet 1809-1892]. Wallace had met Tennyson, was familiar with his writings, and mentioned him from time to time in his own.