Biological parameters of Menochilus sexmaculatus Fab. (Coleoptera: Coccinellidae) feeding on different hosts

The biological parameters of Menochilus sexmaculatus Fab., as influenced by different temperature regimes and hosts were studies at Insectary-Biological Control Labs., Insect Pest Management Programme (IPMP), Institute of Plant and Environmental Protection (IPEP), National Agricultural Research Center (NARC), Islamabad. The result revealed that egg incubation period of M. sexmaculatus reared on Schizaphis graminum Roh. and Rhopalosiphum padi L. was 4.22, 3.64, 2.12 days and 4.16, 3.66, 2.24 days respectively, at 22 plus minus 1 degree C, 28 plus minus 1 degree C and 34 plus minus 1 degree C. Mean fecundity of the beetle was significantly influenced by different temperatures and found as 452, 631 and 473 eggs and 430, 548 and 432 eggs, respectively. Percentage egg hatchability of the predator was significantly higher on both hosts at 28 plus minus 1 degree C. The grub passed through four instars to attain pupal stage. Feeding on two aphid hosts at different temperature did not significantly influence the duration of life stages of M. sexmaculatus, but significantly different at three temperatures. The total larval duration of predator was 9.48, 7.89 and 5.65 days and 9.47, 7.7 and 5.49 days, on respectively at three temperatures. Duration of pupal period ranged between 2.24 - 4.28 days on S. graminum and 2.21 - 4.35 days on R. padi at three temperatures. The pre-oviposition, oviposition and post-oviposition periods were 4.14 to 7.46, 27.57 to 41.78 and 4.39 to 7.59 days on S. graminum and on R. padi were 4.64 to 7.48, 24.99 to 39.93 and 4.76 to 8.09 days, respectively. Life span of adult male ranged from 26.57 to 41.63 and 26.13 to 41.80 days, respectively and of adult female were 36.07 to 56.83 and 34.40 to 55.10 days respectively. All the immature instars were found voracious feeders of two aphid species. However, the third and fourth instars consumed significantly more prey than first and second instars. Mean predatory potential of all larval instars ranged from 161 to 184 and 148 to 162 aphids, respectively. The range of adult male consumed aphids S. graminum and on R. padi from 2468 to 2501 and 2294 to 2422, respectively and female consumed from 3175 to 3356 and 2912 to 3085 aphids, respectively. Stage specific life table of M. sexmaculatus at different temperatures, the development stages of beetle attained minimum apparent mortality, indispensable mortality, mortality survival ratio and maximum survival at 28 plus minus 1 degree C. Similarly, the total generation mortality (K) reared on S. graminum and R. padi was lower at 28 plus minus 1 degree C and higher at 34 plus minus 1 degree C. The present study exhibited that among three different temperatures, 28 plus minus 1 degree C has been proved as a most suitable for the development of M. sexmaculatus.