Mygalomorphs include what are commonly referred to as "tarantulas" (theraphosids) and their allies. Many of these spiders can be quite large. They are often rather "hairy" but this is not universally true. Moreover, there are large "hairy" spiders that are not mygalomorphs (wolf spiders, for example).
Mygalomorphs use silk to line their retreats or to make tube-like structures in which they live. Some species use silken lines that extend from their retreats that act as "trip lines" to alert the spider to prey and enemies and one group makes sheet webs. Although their use of silk can help to catch prey, nevertheless, mygalomorphs do not make catching webs that stick to their prey. They possess neither of the two types of sticky silk. Nor do they possess a type of silk found in araneomorph spiders called piriform silk that allows for the fast attachment of a silken line to the substratum or to other bits of silk. Thus, although mygalomorphs may make extensive use of silk, in many important ways, they are more limited in what they can easily do with their silk than are araneomorph spiders.
Mygalomorphs are often long-lived, especially the females. They possess a number of primitive spider traits (for example, four booklungs) while in other cases they clearly represent a "derived" (more recently evolved) condition -- for example, they only have three pairs of spinnerets (the most primitive spiders have four pairs).