The natural enemies ofSida acutaandS. rhombifoliain Mexico were surveyedover a period of 3 yr. The phytophagous arthropods collected from these plants belonged to 27 families in six orders. Coleoptera accounted for 48%, Hemiptera 27%, Lepidoptera 16%, Diptera 5%, Hymenoptera 2%, and Acarina 2%. Fifty-eight percent reproduced onS. acutaorS. rhombifoliaor both. Twelve species were considered to have potential as biological control agents for these weeds. One,Calligrapha pantherinaStål, has been released in Australia and is causing extensive defoliation ofS. acuta. Prospects for biological control of these weeds are favorable.