Effect of temperature and host-parasite ratio on sex differentiation of Romanomermis iyengari (Welch), a mermithid parasite of mosquitoes.

The effect of temperature and host-parasite ratio on the percentage infection and sex differentiation of R. iyengari was studied. Significant differences were observed in the percentage infection due to different host-parasite ratios and temperatures. At 25 degrees and 30 degrees C, the host parasite ratio of 1:3 resulted in 86-92% infection of Culex quinquefasciatus larvae. At 20 degrees and 35 degrees C, a higher host-parasite ratio was required to get this level of infection. More number of post-parasites per mosquito larva emerged at 20 degrees (1.5-5.8) and 25 degrees C (1.9-6.3) than at 30 degrees (1.5-3.9) and 35 degrees C (1.6-3.6). More than 50% of the post-parasites were females at 20 degrees and 25 degrees, 30 degrees and 35 degrees C at 1:1-1:10, 1:1-1:4 and 1:1-1:3 host-parasite ratios, respectively.