Green bees are small and slender. Females are entirely bright green. The males have a bright green thorax and yellow and black striped abdomen. They mate in late summer, early fall and the pregnant females hibernate over the winter. They then begin a new nest in spring for their young.
You might spot a green bee in your garden if you grow the following: grindelia (gumweed), erigeron (fleabane), coreopsis (tickseed), and cosmos.
I spotted this green bee in my Maine garden where I did have many cosmos and coreopsis, although he is perched on a cone flower. I did spy one last summer in my garden here but of course, did not have my camera. They are so striking and hard to miss. I hope to see more this year.