Biology and demography of Trissolcus basalis (Hym.: Scelionidae) on eggs of two different hosts

A study was taken up to investigate the biological and population attributes of Trissolcus basalis (Wollaston) on eggs of Eurygaster integriceps Puton (EI) and Graphosuma lineatum (L.) (GL). First، immature development، time of adult eclosion، offspring sex ratio and rate of emergence were recorded by random selection of 25 parasitized egg masses of each host (350 eggs with 0-4 h old) separately at 25 ± 0. 5 °C، 65 ± 5% RH and 16:8 L: D. In addition، percent parasitism، immature survival rate، adult longevity and first 10 days fecundity of females were calculated using 25 newly emerged pairs (0-4 h) confined in tubes and provided with two masses of respected host eggs daily under the same conditions till they died. Results revealed that T. basalis males had significantly shorter development period (11. 75 ± 0. 058 and 12. 57 ± 0. 96 d on EI and GL eggs، respectively) compared to that of females (12. 62 ± 0. 06 and 13. 72 ± 0. 69 d on eggs of EI and GL، respectively). Similarly، it was noticed that males’ longevity (54. 72 ± 1. 63 d) on EI eggs was significantly higher compared to their sibling females (43. 16 ± 2. 045 d) and male and female wasps on GL eggs which had significantly shorter longevity. In general، T. basalis reared on EI eggs had significantly longer oviposition period (39 ± 1. 79 d)، higher fecundity (292. 4 ± 11. 14 egg/female) and greater % parasitism (84. 09 ± 1. 56%) when compared with those on GL eggs. Moreover، immature survival rate was 82 and 64 % for wasp reared on EI and GL eggs، respectively. Finally، rm، λ and R0 were 0. 316 and 0. 224 d-1، 1. 372 and 1. 252 d-1 and 118. 5 and 51. 08 f/f/gen for wasps on EI and GL eggs، respectively. The population age distribution demonstrated that، totally، 95-98 and 2-5 % of the population were immature and adult stages for both hosts.