Biologia e exigências térmicas de Spodoptera cosmioides (Walk.) (Lepidoptera: Noctuidae)

Abstract

The biology of Spodoptera cosmioides (Walk.) was studied under different temperatures and its thermal requirements were determined, aiming to aid the rearing of this insect in the laboratory. Embryonic and post-embryonic periods were evaluated at seven different temperatures (14, 18, 22, 25, 28, 30 and 32°C) under environmental chamber conditions, with 14h photophase. The caterpillars were reared on an artificial diet containing white bean, soybean meal, yeast extract, wheat germ and powder milk as source of protein. The extent of the embryonic period decreased with the increase of temperature within the 14°C to 25°C temperature range, remaining constant between 28°C and 32°C. For the other phases (caterpillar, pre-pupa and pupa) an inverse relationship between temperature and duration was observed within the 14°C to 30°C temperature range, extending to 32°C for pupae. Duration of pupal phase for males was larger than for females resulting in asynchronous adult emergence. The temperature thresholds for the embryonic, larval, pre-pupal, pupal periods and total cycle were 9.34°C, 11.65°C, 9.65°C, 11.08°C and 11.23°C, with thermal constants of 62,73 degree-days (DD), 254.61DD, 33.42DD, 177.55DD and 525.11DD, respectively. Evaluating the pupal phase alone, the threshold temperatures were 11.25°C for males and 10.81°C for females, with thermal constants of 188.26DD for males and 165.47DD for females. For total cycle, the threshold temperature and the thermal constant for males were 11.28°C and 535.85DD, whereas for females the same variables had values of 11.15°C and 513.17DD. So, the most adequate temperature for the development of S. cosmioides is within the range of 25°C and 28°C, where 9.6 to 11.7 generations of the insect can be annually obtained, in laboratory conditions.