Seed-feeding species of Megastigmus (Hymenoptera: Torymidae) associated with Anacardiaceae

Four species of Megastigmus Dalman have been reported as phytophagous in seeds of the plant family Anacardiaceae: M. pistaciae Walker, M. rhusi (Hussey), M. thomseni (Hussey), and M. transvaalensis (Hussey). All are Old World in origin. In this paper we summarize known host and distribution data for each species, place Megastigums rhusi as a junior subjective synonym of Megastigmus transvaalensis, diagnose and illustrate all species, and provide a key to aid in the identification of females and, to some extent, males. Known host-plant genera are: Pistacia L., Rhus L., Schinus L., Ozoroa Delile, and Lannea A. Richard. Megastigmus pistaciae and M. transvaalensis have been accidentally introduced into the New World. The former has long been established in California and is reported for the first time from Mexico; the latter is widely established, through host-shifting, in the states of Hawaii, California, Florida, and in Brazil and Argentina.