For those who have a smartphone or a pad, I recommend you quickly go to the Nature Share page of the iTunes store or Google Play. Four of the best Audubon apps are available for $1.99 each through the 4th of July weekend. These are photo guides and I find the apps far superior to the book version of the same title. I was especially surprised at the number of bird vocalizations on my California Birds app.
I only look at the butterflies app occasionally but it’s great having it in my pocket for those occasions. Check carefully. Not all apps are available both for iPad AND Android.