The Question:

What is the difference between a wasp and hornet?

The Answer:

Essentially, the term "hornet" (like "yellow jacket") refers to a kind of wasp that builds a large papery nest.

One type of hornet, the baldfaced hornet, is black and white and about ¾" long. They tend to build mottled grey nests in trees or shrubs. Occasionally, they will build nests under roof overhangs, in attics, crawlspaces, and walls, or under decks or porches. The nests, which are generally pear-shaped, are constructed of a paper-like material formed from chewed wood. These hornets like to feed on flies and other insects." long. They tend to build mottled grey nests in trees or shrubs. Occasionally, they will build nests under roof overhangs, in attics, crawlspaces, and walls, or under decks or porches. The nests, which are generally pear-shaped, are constructed of a paper-like material formed from chewed wood. These hornets like to feed on flies and other insects.

Yellow jackets, by contrast, are only the size of house flies, with distinct yellow and black markings. They build a very similar nest, but it is tan in color, smaller in size than a hornets' nest, and is usually found in an underground cavity, such as an abandoned rodent burrow. Occasionally, yellow jackets will nest in attics or walls. Yellow jackets are scavengers, and are usually encountered at cookouts and around dumpsters and trash barrels.

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—The Fact Monster