Aspectos biológicos de Chrysoperla externa (Hagen, 1861) (Neuroptera Chrysopidae) alimentada com lagartas de Alabama argillacea (Hübner, 1818 (Lepidoptera: Noctuidae) em diferentes temperaturas

Abstract

This work was designed to study some biological aspects and the predatory capacity of larvae of Chrysoperla externa (Hagen, 1861) fed on first instar of Alabama argillacea (Hübner, 1818) larvae. The experiment was conducted at the Insect Biology Laboratory of the Department of Entomology of the Federal University of Lavras (UFLA) MG, in climatic chambers at 15, 20, 25 and 30 ± 1 °C, RH of 70 ± 10 % and 12-hour photophase. It was found that the total predation increased from 390.7 ± 7.8 to 495.4 ± 10.5 larvae when temperature decreased from 30 to 15 °C and the daily predation presented an inverse response. Third instar larvae, preyed on the average, upon 78 % of the total at all the temperatures studied. The weight was variable in all the stages of the development of C. externa and at all temperatures, it being directly proportional to the increase of this factor tending toward stabilization from 25 °C. The duration of all the stages was inversely proportional to the increase of temperature. The total duration of larval development was 33.7 ± 0.4 days at 15 °C reaching 9.8 ± 0.2 days at 30 °C; the period of egg to adult was of 20.1 ± 0.3 days at 30 °C and 76.5 ± 0.6 days at 15 °C, therefore, about 3.8 times longer. The survival rate of the immature stages of C. externa was of 80 %, but at 30 °C, it was 60 %. The percentage of hatched eggs obtained from adults kept at each temperature was greater at 25 °C (86.2 %). The threshold temperatures and the thermal constants ranged for the different stages of C. externa from 4.7 to 11.2 °C and from 40.4 to 412.9 degree-days. It was found that C. externa possesses a great potential as a biological control agent of A. argillacea larvae, adapting itself to different temperatures but, for the laboratory rearing the temperature of 25 °C proved to be the most adequate.