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The insects of the beetle family Chrysomelidae are commonly known as leaf beetles, and include over 37,000 (and probably at least 50,000)[citation needed] species in more than 2,500 genera, making up one of the largest and most commonly encountered of all beetle families.

Numerous subfamilies are recognized, but the precise taxonomy and systematics are likely to change with ongoing research. Leaf beetles are partially recognizable by their tarsal formula, which appears to be 4-4-4, but is actually 5-5-5 as the fourth tarsal segment is very small and hidden by the third. As with many taxa, no single character defines the Chrysomelidae; instead, the family is delineated by a set of characters.

Some lineages are only distinguished with difficulty from longhorn beetles (family Cerambycidae), namely by the antennae not arising from frontal tubercles. Adult and larval leaf beetles feed on all sorts of plant tissue, and all species are fully herbivorous. Many are serious pests of cultivated plants, for example the Colorado potato beetle (Leptinotarsa decemlineata), the asparagus beetle (Crioceris asparagi), the cereal leaf beetle (Oulema melanopus), the mustard beetle (Phaedon cochleariae) and various flea beetles, and a few act as vectors of plant diseases. Others are beneficial due to their use in biocontrol of invasive weeds. Some Chrysomelidae are conspicuously colored, typically in glossy yellow to red or metallic blue-green hues, and some (especially Cassidinae) have spectacularly bizarre shapes. Thus, they are highly popular among insect collectors.