Effects of Temperature on Some Biological Characteristics of Hippodamia variegata (Goeze) Reared on Common Pistachio Psylla Agonoscena pistaciae Burckhardt and Lauterer and on Angoumois Grain Moth, Sitotroga crealella Olivier, under Laboratory Conditions

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Insect natural enemies selected for such specific traits as faster developmental times, longer survivor, increased fecundity, and larger body size might be considered during production of biological control agents in certain situations. For instance, traits related to developmental rates may be selected for, if genetically based variation exists within temperature-dependent responses. Hippodamia variegata (Goeze) (Col: Coccinellidae) is one of the most important predators of orchard pests in Iran. In the course of this study, the effect of six constant temperatures i.e. 17.5, 22.5, 25, 27.5, 30 and 32.5 ?C on preimaginal development and mortality of this predator, feeding on Angoumois grain moth, Sitotroga cerealella Olivier (Lep. Gelechiidae) and common pistachio psylla, Agonoscena pistaciae Burckhardt as well as Lauterer (Hem.: Aphalaridae) was evaluated under laboratory conditions (55±5% r.h. and a 16:8 h of photoperiodism). Temperature exerts a great effect on the development and the level of feeding of Hippodamia variegata. Total developmental times at the above-mentioned temperatures were 47.63±1.53, 25.08±0.18, 17.27±0.64, 15.14±0.37, 12.16±0.64 and 11.27±0.39 days on S. crealella vs., 40.11±0.75, 22.68±0.32, 18.6±0.36, 15.5±0.18, 13.9±0.31, and 13.12±0.51 on A. pistaciae, respectively, indicating a significant decrease of developmental time with increase in temperature. Minimum survival rate was recorded for first nymphal instar whereas the survival at third and forth instars along with pupa amounted to a maximum at the above-mentioned temperatures. The results showed significant differences among the six temperatures as regards developmental times. The estimated lower temperature threshold and thermal constant for the entire developmental times, using the ordinary linear model, were estimated. The lower developmental thresholds (T?) of egg, larva, pupa and egg to adult emergence were estimated through linear regression equation to be 11.91, 12.43, 9.63 and 10.31?C respectively. The thermal constants required at the above mentioned periods were estimated as 39.06, 156.25, 57.8 and 285.71, respectively.

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