Dr. Elizabeth A. Bergey and Dr. Eric G. Bright, University of Oklahoma
Modified, with permission, from Invertebrate Anatomy OnLine
copyright 2003 by Richard Fox (Lander University)
Medical Microbiology. 4th edition.,Baron S, editor.
Galveston (TX): University of Texas Medical Branch at Galveston; 1996. Chapter 77, Robert G. Yaeger