Moneilema, or cactus longhorn beetles are a genus of large, flightless, black beetles found in North American deserts of the western United States and northern Mexico.

M. gigas is native to the Sonoran Desert at elevations below 4900 feet (1500m).

[1] The front wings of these beetles are fused forming a single, hardened shell, from which the genus derives its Latin name.

Larvae bore into cactus roots and stems, sometimes killing more susceptible individuals.

Some Moneilema species in central and southern Mexico are reported to be active all year.