Carpenter bees and bumble bees are similar and size and sometimes in coloring.
The carpenter bee is not as fuzzy as the bumble and has only a small amount of hair on its middle abdomen. Some carpenter bee species are all black while some have similar yellow markings to the bumble bee but only on their head. The lower abdomen has little to no hair and appears black and shiny which is why they are occasionally referred to as black bees.
The carpenter bee also has hairier back legs than the bumble bee which, like honey bees, has special structures called pollen baskets to carry pollen back to its nest.