Larval Growth and the Effect of Temperature on Head Capsule Size inLobesia botrana(Lepidoptera: Tortricidae)

Abstract

Laboratory assays were conducted to determine the effect of temperature on head capsule width of L. botrana (Lepidoptera: Tortricidae). One nonconstant and six constant temperatures were assayed. Temperature significantly affected head capsule size. Head capsules were larger at low temperatures (15–21°C) and smaller at high temperatures (24 and 30°C). Nonconstant temperature and 27°C also produced insects with larger head capsules similar to those ones collected at low temperatures. Five instars were recorded at all temperatures, and no overlap was found between mean head capsule widths; however, an overlap of the ranges of head capsule widths was found between L2 and L3 in larvae reared at 24°C. Growth ratios were also relatively constant. Head capsule growth followed Dyar′s rule. Head capsule width–instar relationship was better described by a second-degree polynomial regression equation.