Development of Trissolcus grandis (Thomson) (Hymenoptera: Scelionidae) on Two Factitious Hosts Graphosoma lineatum (L.) and G. semipunctatum (F.) (Hemiptera: Scutelleridae) at Three Constant Temperatures

Trissolcus grandis (Thomson) is the most important egg parasitoid of sunn pest, Eurygaster integriceps Puton in Iran that easily reared on some other pentatomid eggs such as Graphosoma spp. both in laboratory and field conditions. In this study, two factitious hosts, G. lineatum (L.) and G. semipunctatum (F.) were compared in their effect on development and fecundity of T. grandis under three constant temperatures 23, 26 and 29 ± 1 ºC, 50 ± 10% RH, and 16L: 8D h photoperiod. Thermal threshold of the wasp was estimated 17.11 and 16.82 ºC for males and females reared on G. semipunctatum, and 18.82 and 18.47 ºC for those reared on G. lineatum, respectively. Moreover, thermal constant was obtained as 97.09, 109.89, 76.33 and 91.74 day-degrees for the same treatments, respectively. Titration total protein contents of the eggs in these hosts as well as target host, E. integriceps revealed that more than 99% of variations in thermal requirements of T. grandis among the hosts can be attributed to the protein content of eggs alone. Regression lines of developmental rate of the parasitoid met on temperature around 26.5 ºC that may imply this temperature provides the highest fitness for the parasitoid, as the effect of host disappears and no advantage remains among the hosts. In this temperature, the parasitoid develops by the same rate in all three hosts. The highest value of fecundity was revealed 109.4 ± 12.65 on G. semipunctatum and 91.9 ± 10.36 on G. lineatum that obtained at 26 and 29C˚, respectively.