I.S. PATEL AND S.A. PATEL

Biology of the fennel aphid, Hyadaphis coriandri (Das) was studied in laboratory at an average temperature of 30.11°C and relative humidity 81.13 per cent during the year 2006-07. It passed through four distinct nymphal instars. The average body length of first, second, third and fourth instar nymphs measured 0.54 ± 0.04, 0.73 ± 0.03, 0.91 ± 0.05 and 1.14 ± 0.05 mm, with body width of 0.26 ± 0.02, 0.38 ± 0.02, 0.46 ± 0.02 and 0.60 ± 0.04 mm, respectively. The average developmental period of first, second, third and forth instar nymphs were 1.83 ± 0.69, 2.46 ± 0.50, 2.70 ± 0.74 and 1.43 ± 0.50 days, respectively. Total nymphal duration was 8.43 ± 1.30 days. Adult was dark dull yellow to green in colour with a well developed abdomen. The average adult length and width was 1.39 ± 0.03 mm and 0.73 ± 0.03 mm, respectively. The average pre-reproduction, reproduction and post-reproduction periods were 1.76 ± 0.77, 8.43 ± 1.86 and 2.10 ± 1.02 days, respectively. The mean longevity of the adult aphid was observed to be 8.56 ± 1.86 days with a total life span of 16.00 ± 3.08 days. During the life span a female produced 21.13 ± 7.14 nymphs with an average of 5.16 ± 1.53 nymphs per day per female. The fennel aphid could complete 10 overlapping generations on fennel under controlled conditions.