Complex sentence: The genus "Agapostemon" is a common group of Western Hemisphere sweat bees of generally green or blue appearance (head and thorax almost always, sometimes also the abdomen in females, most males have the abdomen yellow banded on a black or metallic background).
Split into simpler sentences: The genus "Agapostemon" is a common group of Western Hemisphere sweat bees. They are of generally green or blue appearance (head and thorax almost always, sometimes also the abdomen in females, most males have the abdomen yellow banded on a black or metallic background).