Culicoides omatus Taylor is one of the main pest species of biting midge in northern Australia (Reye 1992). It has a coastal distribution from the north of WA to the south of Qld. Its breeding sites are known to occur within mangroves and its presence can create a major pest problem for 1.5 km inland of mangrove areas (Reye 1973, Whelan 1990). Although its larval habitat has been shown to occur around mean high water neap (MHWN) within mangroves in eastern Australia (Reye 1992), previous studies near Darwin have been unsuccessful in identifying its larval habitat (Reye and Lee 1962, Leihne et al. 1985). Darwin differs from eastern Australia in having a very high tidal range of approximately 8 m and very pronounced wet and' dry seasons. This paper discusses the results of a 2 yr study into the distribution of the immatures in mangroves near Darwin. Knowledge of the biology of the immatures is necessary for both assessing the potential of control methods aimed at this stage of the midge's life-cycle and to predict the potential pest problems of land adjacent to mangroves.