The effects of certain physical and biological factors on the survival and the hatching rates of Psorophora columbiae (Dyar and Knab) (Diptera: Culicidae) eggs

Typescript (photocopy).The results of laboratory tests indicated diapausing Psorophora columbiae eggs were more tolerant to the low temperatures used (8° to -6°C) than were non-diapausing eggs, particularly at temperatures equal to and below 4°C. However, diapausing and non-diapausing eggs were similar in their ability to survive for extended periods of time under high temperatures (34° and 38°C). High soil moisture content (30-40%) appeared to enhance the ability of the mosquito eggs to survive both low and high temperature extremes. Results of field studies showed that the combination of dry soil (below 20% moisture) and high soil temperature (above 35°C) adversely affected the survival rates of the eggs to a significant degree. Other results from this same field study indicated more suitable conditions for egg survival occurred on the levees than on the pans of rice fields. Results of other studies described herein indicated the predacious habits of red imported fire ants, Solenopsis invicta Buren, on Ps . columbiae eggs may make an important contribution to the natural control of this mosquito species in southern areas of the U.S. where this ant species occurs. The fire ants eliminated 96% of Ps. columbiae eggs on moist soil during 18 hrs. of exposure in the laboratory. Temperature is an important factor affecting the foraging rates and egg predation efficiency of fire ants. In laboratory tests, all mosquito eggs were removed by worker ants within 24 hrs at 30° C and 35°C. The state of embryonation of mosquito eggs appeared to have no effect on the level at which fire ants will prey on eggs. In the field, mosquito egg predation by ants was most intense during the summer months, commensurate with the occurrence of temperatures optimal for fire ant foraging