taxonomy of beetles and freshwater mollusks. In 1840 he began the publication of his Monograph of the Freshwater Univalve Mollusca of the United States, issued in nine parts with the final volume not appearing until 1866. The monograph was well received by the scientific community in America and Europe. In an addendum he described Scolithus linearis, a trace fossil of some burrowing organism, the most ancient organic remains known at the time. In 1844 he wrote a paper, "Enumeration of the Recent Freshwater Mollusca Which are Common to North America and Europe", where he laid out in detail the case for Lamarckian evolution and transmutation of species. In 1861, Charles Darwin wrote in a preface to his On the Origin of Species an acknowledgment of Haldeman's ideas in support of evolution. He was elected as a member to the American Philosophical Society in 1844. In 1842 he was instrumental in the establishment of the Entomological Society of Pennsylvania, the first scientific society formed to study insects in America. Haldeman's participation in the society put him in regular contact with other leading American entomologists including Frederick E. Melsheimer and John G. Morris. His first entomological paper was the "Catalogue of the Carabideous Coleoptera of South Eastern Pennsylvania," published in 1842. Over the next 15 years he published many papers on the systematics of beetles and other insects, describing many new species. His ear was remarkably sensitive, and he discovered a new organ of sound in lepidopterous insects, which was described by him in Benjamin Silliman's American Journal of Science in 1848. In 1852 he wrote a description of the insects collected by the Stansbury survey of the Great Salt Lake. In addition to his work on entomology, Haldeman accepted various college appointments to teach natural history. In 1842 he was a professor of zoology at the Franklin Institute in Philadelphia. From 1851 until 1855 he was professor of natural history at the University of Pennsylvania. He then accepted a similar professorship in Delaware College. Meanwhile, he also lectured on geology and chemistry at the State Agricultural College of Pennsylvania. He visited Texas in 1851 to investigate the presidency of an institution there, but declined the position. On his return trip from Texas, he was offered the position of president of Masonic College in Selma, Alabama, which he accepted and held from January to October 1852. In the 1850s, Haldeman's focus turned