Effect Of Temperature And Food On Fecundity Of Beet Armyworm Spodoptera Exigua

The beet armyworm, Spodoptera exigua (Hiibner) (Lepidoptera: Noctuidae) was a worldwide insect pest that attacks >200 species of host plants in various botanical families. This paper studied the effect of temperature and foods of beet armyworm. The main contents and conclusions were as follows.1. The calling, mating and oviposition behaviors, and reproductive capacity of Spodoptera exigua were studied at 15, 20, 25, 30, 35, and 40℃ in the laboratory. Results indicate that temperature significantly affected the calling, mating and ovipositing behaviors of S. exigua. We found that the calling behavior of the females involved three distinct phases: initiation, excitation, and desire to mate. Mating peaks were postponed by 1.3-1.7 h as the temperature increased from 15℃ to 30℃, but the mating peaks were not significantly different from that at 25℃ as temperature increased to 35 and 40℃. Mating duration shortened as temperatures increased. The mating rate was highest at 25 and 30℃ (96%) and lowest (44%) at 40℃. Temperature significantly affected oogenensis, oviposition, and egg hatching. Total eggs, eggs laid, and egg hatching rates increased as temperatures increased from 15℃ to 30℃, and then declined at 35℃ and 40℃. Remarkable effects were found at 40℃ at which only 13.5% of total eggs were laid, and of these, 37.2% hatched. Preoviposition periods gradually lengthened from 1.2 d at 15℃ up to 3.9 d at 40℃. In contrast, oviposition periods shortened as temperatures increased. The females deposited more eggs hi the first d at 25, 30 and 35℃than at 15, 20 and 40℃. The longevities of both the females and the males were negatively correlated with the temperatures.2. The composition of the subunits of Spodoptera exigua vitellin(Vn) was studied through sodium dodecyl sulfate-polyacrylamide gel electrophorsis (SDS-PAGE). The Vn was composed of large(175kD) and small(60kD) subunits. Immunological cross-reaction results indicated that the Vn was female specific, there was immunological cross-reaction between the vitellin's anti-serum and the Vn of Spodoptera exigua , but no cross-reaction to the haemolymph of the male moths.The dynamics of Vn in ovary from larva to adult death were assayed withone-dimension rocket immunoelectrophoresis. Vn was synthesized and uptaken in ovary. It appeared in ovary since 6th day after pupating, but its content were very low. The content of Vn decreased as reproduction increased.3. High temperature had significant effects on fecundity and ovary development of Spodoptera exigua (Htibner) . Female moths were raised Ihr, 4hr and 8hr under 40℃, 43℃ and 46℃ respectively. The results indicated the eggs laid and eggs hatching rates went down dramatically after female moths were put in so high temperature for 8hr, while short time in high temperature (Ihr and 4hr) hardly affected them. Remarkable effects were found at 46℃ for 8hr at which eggs laid were only 50% and eggs hatching rate was only 9% of the controls. The length of ovary tubes and wet weight of ovaries dropped in some extents under high temperature. Vitellin (Vt) and soluble protein in ovaries were also affected in the way that Vt decreased 43% and soluble protein decreased 23% contrasted with the controls at 46℃ for 8hr. High temperature inhibited the absorption and synthesis of Vt. We also found that Vt content positively correlated with the amount of eggs laid.4. Female pupaes were raised Ihr, 4hr and 8hr under 40 ℃, 43℃ and 46 ℃ respectively. The results indicated 4hr and 8hr under 46℃ significantly effected their development. No healthy moths could emerge under this temperature. High temperature remarkablely affected pupal period, emerging rate and eggs laid. But the effect on eggs hatching rate was unsignificant under high temperature. The eggs laid and eggs hatching rates went downing dramatically after female moths were put in so high temperature for 8hr, while short time in high temperature(lhr and 4hr) hardly affected them.Preoviposition periods gradually lengthened...