Biometrical variations in haematophagous arthropods. II. DV/D ratio of male terminalia of wild Culex quinquefasciatus SAY (Diptera: Culicidae) in India.

The DV/D ratio of male terminalia is considered as most reliable morphometric feature to distinguish Culex pipiens from Cx. quinquefasciatus. In India although only Cx. quinquefasciatus is known both in the filariasis (Bancroftian) endemic and non-endemic areas, there has been no study on the amounts of morphometric variation among wild strains of this species. This paper reports variation in the DV/D ratio of Cx. quinquefasciatus collected from 7 localities of Delhi (D), Lucknow (L), Patna (P), Varanasi (V), Rajahmundry (R), Jabua (J) and Alleppey (A) between June and October 1986. The mean value of DV/D ratio in all the strains varied from 0.78 to 0.99 with overall mean of 0.89. The range of the ratios was 0.30 to 1.88. There were 1.28 per cent specimens (9 out of 700) with ratio below 0.50 and the rest 98.72 per cent with ratio 0.50 and above. The DV/D ratio of 0.50 should therefore be accepted as lower limit for Cx. quinquefasciatus instead of the earlier established value of 0.40. The coefficient of variation (CV) among the 7 strains indicates the following progression of variability in the DV/D ratio from most stable to most variable strain: L greater than V greater than R greater than A greater than J greater than P greater than D. The range of mean CV values in different strains was very close with most stable L strain 19.19 and most variable D strain 25.92. The amounts of variation, as estimated by coefficient of variation, were found to be significantly different between the following strains: Delhi and Lucknow (P less than 0.01 at 198 df), Lucknow and Patna (P less than 0.05 at 198 df), and Delhi and Varanasi (P less than 0.05 at 198 df).(ABSTRACT TRUNCATED AT 250 WORDS)