Crotalus horridus CDC
<a href="//commons.wikimedia.org/wiki/User:Crotalus_horridus" title="User:Crotalus horridus">user:Crotalus horridus</a>
This image is taken from the Public Health Image Library (PHIL), a division of the CDC. The description of the image specifically states that it is in the public domain: "This image is in the public domain and thus free of any copyright restrictions. As a matter of courtesy we request that the content provider be credited and notified in any public or private usage of this image." It is credited to Edward J. Wozniak D.V.M., Ph.D. I downloaded the high-resolution TIFF from the website and re-saved it in the PNG format (compression level 9) using GIMP. This reduced the file size by about half while resulting in no loss of visual information. Original URL: <a rel="nofollow" class="external autonumber" href="https://phil.cdc.gov/PHIL_Images/8162/8162.tif">[1]</a>. Due to the extensive use of server-side scripting on the PHIL website, it is impossible to link directly to the image description page, but it can easily be located by going to <a rel="nofollow" class="external text" href="https://phil.cdc.gov/phil/imageidsearch.asp">this search page</a> and entering the image ID (8162) in the search box.