He was also one of the first American scientists to support Charles Darwin's theory of evolution and was instrumental in securing its broad acceptance in the entomological community.

[3] When Walsh was a boy, his father, a member of parliament, was charged with embezzlement and caught attempting to flee to America without his wife and children.

A scholar of classic languages and literature, Walsh wrote The Comedies of Aristophanes, Translated into Corresponding English Metres (the first of an intended three volumes).

Worried for his health, Walsh moved to Rock Island, Illinois, in 1850 and started a successful lumber business.

Initially, perhaps influenced by his own farming experience, Walsh focused on the practical aspects of insects as agricultural pests.

These works provided detailed observations of insect metamorphosis and natural history; compared morphological characters for a given taxon; or described new species.

Targeting farmers, this monthly journal featured illustrations and clear descriptions to help readers identify insect pests and apply the most effective controls.

Two significant findings by Walsh and Riley appeared in this journal: the discovery of the 13-year form of the periodical cicada, and the first reference to mimicry of the North American monarch butterfly by the viceroy.

Although not close friends, they were acquaintances, held a shared interest in natural history, and were mentored by two prominent Cambridge professors: geologist Adam Sedgwick and botanist John Henslow.

Once Walsh became convinced of Darwin's theory, he championed the cause vigorously in the American scientific community through his lectures, publications and private correspondence.

With Darwin's encouragement, he challenged the views of prominent opponents of evolution, including Louis Agassiz, Samuel Scudder, and Alpheus Packard.

Within a few years, most entomologists (including Scudder and Packard) were expressing their support for evolutionary theory, while the remaining holdouts, like Agassiz, experienced a diminished reputation with their peers.

[7] Walsh also incorporated evolutionary thinking into his own entomological studies and made several original contributions supporting Darwinism.

[6] His insect collection, numbering 30,000 specimens, was purchased by the state of Illinois and stored in the "fireproof" facilities of the Chicago Academy of Sciences for safekeeping.