Energy reserves in Brevicoryne brassicae (Lin.) (Homoptera: Aphididae) instars and their effect on predation and longevity of three coccinellid species under laboratory conditions

Background Contents of carbohydrates, protein, and lipids in tissues of insect prey constitute the required energy reserve utilized by their predators. Their amounts define the preference of the predator to certain prey on which its biological performance is the optimum. Feeding preferences and longevity of the 3 coccinellid beetles; Coccinella septempunctata L., C . undecimpunctata L., and Scymnus interruptus L. were studied in relation to energy reserve in tissues of the cabbage aphid, Brevicoryne brassicae (Lin.). Main body The level of energy reserve increased with increasing of aphid nymphal instars showing the highest in 4th instar (0.10844 cal/mg). Lipids and carbohydrates represented the highest energy reserve average rate in B . brassicae adults (0.29139 and 0.07404 cal/mg), respectively. C . septempunctata larval stage recorded the highest efficiency in daily predation (89.42 prey), when fed on 1st instar nymphs of the aphid. It required 21 days when fed on the 3rd nymphal instar of B . brassicae . S . interruptus larval stage reflected the lowest consumption and longevity in predation where it consumed less than 69.25 prey/day and lasted a period less than 17.5 days. Generation time for C . undecimpunctata lasted the longest (20.89 days) when fed on B . brassicae 1st nymphal instar. It was decreased in S . interruptus recording (12.22 days) when fed on B . brassicae 3rd nymphal instar. Conclusion Only C . septempunctata was efficient in predation and its biological performance was the best compared to the other tested coccinellid species. Use of C . septempunctata can be recommended when applying biological control programs in the field against the cabbage aphid.