Like other ambrosia beetles, they feed on ectosymbiotic fungi which they introduce into their tunnels and cultivate and not the wood and pith of their hosts. Eggs, larvae, and pupae are found together in the tunnel system excavated by the female. There are no individual egg niches, larval tunnels, or pupal chambers. It breeds in host material from 2 to 30 cm in diameter, although small branches and stems are most commonly attacked. Attacks may occur on apparently healthy, stressed, or freshly cut host material.
High humidity is required for successful reproduction.
Females remain with their brood until maturity. Males are rare, reduced in size, flightless, and presumably haploid. Hosts X. crassiusculus is capable of breeding in a wide variety of hosts. Known hosts in the U.S. include peach, plum, cherry, persimmon, golden rain tree, sweetgum, Shumard oak, Chinese elm, sweet potato, and magnolia. Bradford pear and pecan as hosts commonly attacked in Florida and in the Southeast.