With the exception of
Pharaxonotha kirschii, all species of
Pharaxonotha are obligate
symbionts of species of
cycads in the Americas in the genera
Ceratozamia,
Dioon,
Microcycas, and
Zamia. The beetles live and breed in the pollen
strobili (reproductive cones) of male plants (cycads are
dioecious, with male and female cones on separate plants), consuming pollen and the tissues of cones. They also transfer pollen from the male plants to
ovule strobili on female plants. The beetles have been associated with
cycads since the early
Jurassic, about 200 million years ago. Cycads are
thermogenic, capable of raising the temperature of at least some tissues. In particular, thermogeneis has been observed in the male (
pollen) and female (
ovule) cones (
strobili) of
Zamia plants. Male cones ready to shed pollen heat up early in the evening, and then cool down, while receptive female cones heat up about three hours later and then cool down.
Pharaxonotha beetles have receptors for
infrared radiation on their
antennae, by which they appear to detect the elevated temperature of the cones on
Zamia plants.
Pharaxonotha beetles have been observed moving to cones on male plants when the cone's temperature is elevated, crawling into openings in the cone and emerging covered with pollen, and then moving to the cones on female plants when their temperature is elevated, again crawling into openings in the cone, presumably transferring the pollen. Each
Pharaxonotha species typically pollinates just a few closely related cycad species. ==Life cycle==