What are the primary physical differences between carpenter bees and bumblebees?

The primary physical difference that distinguishes carpenter bees from bumblebees is that carpenter bees have shiny black, hairless abdomens. This characteristic is crucial for identifying them; while carpenter bees are often mistaken for bumblebees, their smooth, glossy abdominal surface is a defining feature. In contrast, bumblebees have furry abdomens that are typically covered with dense hair, which is useful for their role in pollination.

Although other options mention various traits, they do not correctly highlight the distinct physical characteristics that differentiate the two species. For example, bumblebees are generally larger and have a more robust body compared to carpenter bees, but they are not necessarily more aggressive. Additionally, carpenter bees are not smaller or more colorful than bumblebees, as the latter are known for their varying color patterns that include yellow and black stripes. Lastly, bumblebees are not devoid of hair; in fact, their hairiness is one of the reasons they are effective pollinators, contradicting the claim in the options. Thus, recognizing the shiny, hairless abdomens of carpenter bees is key to accurate identification.