EFFECT OF TEMPERATURE ON DIFFERENT STAGES OF ROMANOMERMIS-IYENGARI, AMERMITHID NEMATODE PARASITE OF MOSQUITOS

The effect of temperature (20 degrees-35 degrees C) on different stage s of Romanomermis iyengari was studied In embryonic development, the s ingle-cell stage eggs developed into mature eggs in 4.5-6.5 days at 25 -35 degrees C but, required 9.5 days at 20 degrees C. Complete hatchin g occurred in 7 and 9 days after egg-laying at 35 and 30 degrees C, re spectively. At 25 and 20 degrees C, 85-96% of the eggs did not hatch e ven by 30th day. Loss of infectivity and death of the preparasites occ urred faster at higher temperatures. The 50% survival durations of pre parasites at 20 and 35 degrees C were 105.8 and 10.6 hr respectively. They retained 50% infectivity up to 69.7 and 30.3 hr: The duration of the parasitic phase increased as temperature decreased. Low temperatur e favoured production of a higher proportion of females which were als o larger in size. The maximum time taken for the juveniles to become a dults was 14 days at 20 degrees C and the minimum was 9 dyas at 35 deg rees C. Oviposition began earlier at higher temperature than at lower temperature. However its fecundic period was shorter at 20 degrees C t han at 35 degrees C indicating enhanced rate of oviposition at 20 degr ees C. Fecundity was adversely affected at 20 degrees C and 35 degrees C. It is shown that the temperature range of 25 degrees-30 degrees C favours optimum development of R. iyengari.