I can honestly say they are not Garters.
Garter snakes are of the species Thamnophis.
I own Thamnophis.net, Thamnophis.us & Thamfriends.com, Our good friend Jason (Boots) the other moderator here owns Thamnophis.com
My screen name is taken from Thamnophis Sirtalis Infernalis, The California Garter snake.
I'm not trying to brag or boast, just establishing that there is not a Garter snake species on the planet that I cannot identify on sight.
Google only searches the web for words, If someone who does not know what they photographed calls it a garter snake, Google will attach the name to the picture.
This is also why no one should ever take Wikipedia as gospel, anyone can type anything they want on there, and it's not necessarily always true.
Back to the green snakes, yes they will eat crickets, however there is an enzyme present in spiders that insects lack, Green snakes need that enzyme or their health slowly deteriorates and generally within a year the snake will die.
Just like certain fish contain an enzyme called Thiaminase that blocks thiamin absorption within the snakes that eat fish, and the snake will ultimately have an abbreviated lifespan from thiamin deficiency.
The worst 2 kinds of fish anyone could feed to garter snakes or water snakes is goldfish and rosy reds, yet for some messed up reason, quite a few pet shops will actually recommend feeding goldfish or rosies to pet garter snakes?? Those fish contain very high levels of Thiaminase.