Soil application of heptachlor had significantly more destructive effects on ground-inhabiting predaceous arthropods (especially on ants) than endrin or azinphosmethyl in sugarcane fields in Louisiana. Ant populations were significantly lower in endrin- than in azinphosmethyl-treated plots. No difference in spider populations was recorded in plots treated with either endrin or azinphosmethyl. Azinphosmethyl had the least drastic effects on predator populations, particularly ants. Generally, percentages of joints bored by the sugarcane borer, Diatraea saccharalis (F.), as well as percentages of infestation, were found to be negatively correlated with numbers of predaceous soil arthropods. Increase in damage by the sugarcane borer in heptachlor-treated plots was mainly due to the suppression of predator populations. Direct observations in the field indicated that ants are among the more important natural control agents that determine the degree of infestation by the sugarcane borer A list of the species of predators collected during the summer of 1965 from pitfall traps situated at Cinclare Plantation, West Baton Rouge Parish, Louisiana, is presented. Six of the species of spiders collected had not previously been reported to occur in Louisiana.