A study was conducted during 'Kuruvai' crop season from December 1992 to January 1993 in the rice fields of the Agricultural College and Research Institute, Madurai, Tamil Nadu to determine the influence of plant spacing and plant canopy on the populations of mosquito immatures. Three paddy varieties (ADT36, IR50 and IR20) were selected with two types of plant spacing, one with normal spacing (15 x 10 cm) and another wider (20 x 15 cm) than the normal spacing. Results showed that the field planted with normal spacing of paddy had significantly higher populations of culicine and anopheline immatures than the fields planted with wider spacing of paddy. The paddy varieties did not have any significant effect on the population of mosquito immatures. Light intensity, measured at the water surface using an illuminometer, was inversely related to the development of plant canopy and the results suggested that plant canopy does not inhibit oviposition by mosquitoes in the early stages of paddy growth, but it was responsible for the decline in the populations in the later stages of paddy growth. The plant spacing had a significant effect on the populations of chironomids and libellulids and other insects were not affected significantly.