Ambrosia beetles are an ecological guild rather than a phylogenetic group, and include members of the family Curculionidae in the subfamilies Scolytinae and Platypodinae.
Ambrosia beetles are highly derived weevils that employ a unique habit. They bore galleries in the trunks of trees, but rather than feeding on the wood, they cultivate ambrosia fungi in the galleries and feed on the fungus instead. The adults are small, less than 5 mm long, and they look superficially like powder-post beetles; that is, they are elongate and mostly cylindrical in shape, and sometimes the head is pointed downward and invisible from above, particularly in the Scolytinae. They may be yellowish to reddish-brown in color. Adults can be differentiated from powder post beetles by their elbowed, clubbed antennae, and four visible tarsomeres. The larvae are similar in appearance to other weevils, being grublike, footless, and white to cream-colored. Scolytinae larvae are generally C-shaped while Platypodinae larvae are rectilinear.
Worldwide, most diverse in the tropics; about 3,000 species
The adult beetle bores into the stem of the palm, forming brood chambers where they overwinter. In spring, some adult females mate with apterous males and emerge from the tree at night to find a new suitable host. Unmated females may produce haploid males with whom they mate, producing only female progeny. Gallery formation may be initiated by either sex, depending on the species. Colonies of the symbiotic fungus are cultivated in the galleries, and the adults and their brood feed upon these colonies. Females lay eggs, which hatch in 6-10 days. The larvae will often form their own pupal chamber, emerging as adults usually within 2-4 weeks of hatching.
Palms: a wide variety of palms
Other: a wide variety of trees
Platypus parallelus (subfamily Platypodinae) is a tropical species that is one of the most commonly collected beetles from dead or weakened palms in Florida.
Xyleborus ferrugineus (subfamily Scolytinae) is one of the most common, widely distributed, and economically important ambrosia beetles in the world. It is an alleged pest of coconut palm but primarily attacks recently killed or dying trees.
Ambrosia beetles are almost always considered secondary pests, feeding almost exclusively on dead or dying trees.