Each spring, or vernal equinox. we celebrate what has been called the moveable feast. This includes Easter and Passover. The dates for the equinox, (when day and night are equal in the northern hemisphere), have changed over the years beginning with Julius Caesar in 45 BC. He had fixed the date of the equinox at March 25th, but that began to drift as the calendar did not fit the universe. But, that was corrected by Pope Gregory XIII with what we now know as the Gregorian calendar. But, for many of us it is the end of winter and time for outside activities. Just in time before we all go crazy! Image courtesy of Dover Publications.

Each time I do a post entry I try to include a photograph or illustration to highlight the subject. And, for the majority of my posts I do my own photography or illustration. But, there are times when I really need something more professional or the subject is not easy for me to photograph. For example, if I wanted to do a post on dung beetles, I would be lost! I do not have dung beetles or easy access to these insects. So, I have to look around for a public domain source as I really could not justify paying for a commercial photo. Two sources that I have mentioned before are WPClipart, and Dover Publications. But, I can always use more material to find suitable images.
I have known for a long time that a good source of both videos and images is the US government. And, for the vast majority of material that has been funded by taxpayers, it is quite probably in the public domain which means that there is not a copyright and can be used freely. But there is a caveat to be aware of when using these images. The government sometimes pays for images to be used in publications but the image remains in the photographers control and may be copyrighted. So a little digging may be necessary to find out if it is truly in the public domain.
Having said all of that, I did find a United States Department of Agriculture site, the Agricultural Research Service, (ARS), that seems to be totally in the public domain. There are about 2,000 images of flowers, insects, and a lot more here.
But, if you use any of these photos it would be a common courtesy to credit the photographer when that information is available. The lead photo here is of orchids and anthuriums, by Scott Bauer. These images are available in several resolutions and some are quite spectacular. Happy hunting!