Horace Haldeman, soldier, rancher, and early insect collector in Texas, the son of Henry and Frances (Stedman) Haldeman, was born on August 14, 1820, near Marietta, Lancaster County, Pennsylvania. Several members of his family, of Swiss descent, served in important positions during revolutionary and colonial times. In his early life he was a surveyor on the Pennsylvania Central Railroad, a farmer, and part owner of a steel furnace in Pennsylvania. He enlisted in the United States Army on February 16, 1847, and served in Mexico with the Eleventh Infantry during the Mexican War. During the war he collected insects at Jalapa and Tampico for his brother. He returned from Mexico in 1848 and after a few months in Pennsylvania joined the Eighth United States Infantry in Port Lavaca, Texas, on December 27, 1848. In Texas he served at several frontier outposts, including Port Lavaca, Fort McKavett, San Antonio, and Fort Gates. Haldeman collected insects at several of these localities, especially at Fort Gates, where he was acting assistant quartermaster and post adjutant from 1848 to 1850 and commanding officer in early 1852. He left Texas in 1854 and served at Fort Columbus, New York, until he resigned from the army on February 1, 1856. He returned to a ranch on Elm Creek, Bell County, Texas, and engaged in livestock and horse ranching. He served in the Confederate Army during the Civil War and later moved to Belton and then to Calvert, where he ran a livery stable until his death.
Haldeman was one of the first persons to concentrate on collecting insects in Texas. He sent his specimens, mostly beetles, to his entomologist brother, Samuel S. Haldeman, and a noted coleopterist, John L. LeConte, for description. The weevil Lixellus haldemani Burke and at least two other beetles were named in recognition of Haldeman's collecting in Texas. Haldeman married Annie B. Haynes (or Haines) at Marietta, Pennsylvania, on February 8, 1842. They had five children. Haldeman became a Catholic during the Mexican War. He died on September 11, 1883, and was buried at Calvert.