The earliest classification of the genus Linguatula was in 1789 by Froelich. Numerous Linguatula-related classifications occurred between 1789 and the early 1900s. These include classification of Linguatula serrata in 1789 by Froelich, and Linguatulina, a separate order for Tongue-worms, by Hayck in 1881 (Sambon, 1922).
Figure 2. An early sketch of Linguatula serrata showing its distinctive characteristics: (a) anterior extremity; (b) posterior extremity; (i) intestine; (v) utero-vagina (Sambon, 1922).