Vertical distribution of immature Psychoda alternata in soil to a depth of 15 cm was studied in Jacksonville, FL. Samples were randomly taken from large circular land areas receiving a brewery wastewater utilized for commercial turf cultivation and included turfed and bare habitats. Total organic matter was quantified at various soil depths. Overall, 88.5 and 95.8% larvae and 91.3 and 94.0% pupae were recovered from the top 2.5 cm of soil at turfed and bare habitats, respectively. The highest concentration of total organic matter at both habitat types was in the top 2.5 cm. There were strong positive relationships between the number of larvae and pupae and total organic matter, indicating highest concentrations of immatures in nutrient-rich topsoil with an abundant supply of larval food. We suggest that insecticidal treatment directed against immature P. alternata breeding in such habitats need not penetrate to a depth of more than a few centimeters to affect almost all of the population of this pestiferous insect.
