Thaddeus William Harris, an American naturalist, born in Dorchester, Mass., Nov. 12, 1795, died in Cambridge, Jan. 16, 1856. He graduated at Harvard college in 1815, studied medicine, and practised his profession at Milton Hill till 1831, when he was appointed librarian of Harvard college. For several years he gave instruction in botany and general natural history in the college, and he originated the Harvard natural history society for the students. He was chiefly distinguished as an entomologist. In 1837 he was appointed one of the commissioners for a zoological and botanical survey of Massachusetts, the result of which was his "Systematic Catalogue of the Insects of Massachusetts " appended to Prof. Hitchcock's report. In 1841 appeared his "Report on Insects Injurious to Vegetation," published by the legislature. It was reprinted in 1852, somewhat enlarged; and a new and enlarged edition, by Charles L. Flint, with engravings drawn under the supervision of Prof. Agassiz, by direction of the legislature, appeared in 1862.