Laboratory and semi-field studies were conducted to investigate some biological parameters, feeding
capacity and releasing efficiency of Hippodamia convergens on legume aphid, Aphis craccivora. At 25±2˚C and
65±5 R.H., durations of the eggs' incubation period, the four larval instars and pupae were 4.48, 2.11, 2.23, 2.23,
2.68 and 4.39 days, respectively. The average feeding of the 4th instar larvae fed on 84.47 aphids of 4
th nymphal
instar, being the highest voracious feeder compared to the first three larval instars which consumed the means of
14.4, 21.3 and 32.87 individuals, respectively. When fed on A. craccivora nymphs, female survived longer
(50.83 days) than male (34.73days), a single H. convergens female deposited average total of 455.13eggs.
The semi-field studies evaluated the controlling capacity against infestation by A. craccivora on faba
bean seedlings by H. convergens released under greenhouse conditions, as; only adults, only 3rd instar larvae and
both stages. Either of the three treatments for releasing Hippodamia caused reductions of aphid densities than
control. In experiment one; 3, 9 and 15 adults/plot were released only one time. Ten days after release, the
treatment receiving 15 adults/plot showed the highest reduction rate in aphids (100.00%) compared to that
received 3adults (86.78 %) or 9 adults (95.41%) /plot. In the second treatment; 3, 9 and 15 larvae/plot were
released one week after infestation, reduction rate of 96.93% occurred 10 days after releasing of15 larvae/plot.
In the third experiment; both stages altogether were released at 3 ratios, i.e., 1adult:2 larvae, 3 adults:6 larvae
and 5adults: 10larvae/plot. The highest reduction rate (99.14%) of A. craccivora occurred by the third treatment
(5A:10L/plot) after 13 days from the releasing date. Treatment receiving only adults showed the highest
reduction rate of A. craccivora densities compared to the two other treatments. Accordingly, releasing H.
convergens adults only was better than the other two treatments for control of A. craccivora infestations.
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