Technical Abstract: During surveys for natural enemies that could potentially be used as classical biological control agents of Schinus terebinthifolius Raddi (Brazilian pepper) which is invasive in the USA, the caterpillar, Tecmessa elegans Schaus (Lepidoptera: Notodontidae), was recorded feeding on the leaves of the shrub in South America. Descriptions of the biology and larval and adult host range of this species were conducted to determine the insect’s suitability for biological control of this invasive weed in North America. Biological observations indicate that the larvae have five instars. When disturbed, the late instar larvae emit formic acid from a prothoracic gland which may protect larvae from generalist predators. Larval host range tests conducted both in South and North America indicated that this species feeds and completes development primarily on members of the Anacardiaceae within the tribe Rhoeae. Oviposition tests indicated that when given a choice in large cages the adults will select the target weed over Pistacia spp. However, considering the many valued plant species in its host range, especially several North American natives, this species will not be considered further for biological control of S. terebinthifolius in North America. Further studies on the field host range could confirm preliminary observations that this insect is a specialist on only a few species of Schinus and Lithrea.