not ratified by the legislature until nearly a year later, Walsh began work immediately. In 1865 the Entomological Society of Philadelphia established a monthly periodical, the Practical Entomologist, the first American journal devoted to economic entomology. Walsh was appointed an associate editor and quickly became editor of the short-lived but influential publication. In September 1868 Walsh became senior editor of The American Entomologist, with C.V. Riley as junior editor. 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. Darwinism Walsh had been classmates with Charles Darwin at Cambridge and both received their baccalaureate degrees in 1831. 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. Walsh first read Darwin's On the Origin of Species in 1861. He had initially approached the book with skepticism but quickly became a convert to Darwin's theory and one of its most enthusiastic proponents. He later wrote to Darwin: "Allow me to take this opportunity of thanking you for the publication of your Origin of Species... The first perusal staggered me, the second convinced me, and the oftener I read it the more convinced I am of the general soundness of your theory." This was the first letter in what became a regular correspondence. Over the next several years more than 30 letters were exchanged between them. 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. Walsh also incorporated evolutionary thinking into his own entomological studies and made several original contributions supporting Darwinism. In 1864 Walsh noted that 15 similar species of gall-inducing insects differed primarily in their preference for different species of willow. He went on to argue that these