Age-specific Developmental times for Pink Bollworm (Lepidoptera: Gelechiidae): Three Age Classes of Eggs, Five Larval Instars, and Pupae

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Abstract
Developmental times of white, orange, and head capsule age classes of pink bollworm (PBW), Pectinophora gossypiella (Saunders), eggs, five larval instars, and pupae were determined at selected constant temperatures ranging from 20.0 to 35.5°C. Within the egg stage, the orange age class required the longest time to complete development, ca. 50–60% of total egg developmental time. Although most larvae (84–92% of each cohort) developed through only four instars, five instars were also observed for each temperature tested, and at 33.5°C two larvae developed through six instars. The effect of an additional instar increased developmental times 3–6 days for the complete larval stage. At each temperature, developmental time among each of the first three (for four-instar larvae) or four (for five-instar larvae) instars was essentially the same; however the last instar (either fourth or fifth) required ca. 2- to 2.5-fold longer to complete development. Analysis of the developmental rate/temperature relationship for the egg, larval, and pupal stages yielded average lower developmental thresholds of 13.10, 12.38, and 11.69°C, respectively. Degree-day requirements for each age class are reported.