Longevity and fecundity in the colorado potato beetle, leptinotarsa decemlineata
PEFEROEN, M. | HUYBRECHTS, R. | LOOF, A.
Longevity, egg production and sensitivity towards induction of diapause of two laboratory cultures of Leptmotarsa decemlineata Say, the Colorado potato beetle, were compared. One culture was kept ab ovo under long-day conditions (LD: 16 hr pholophase; 25° = LD culture); the other was raised ab ovo in short-day conditions (SD: 10 hr photophase; 25°), kept in diapause during 9 months at 25° in dry sand and after termination of diapause brought to LD (= DP -- LD culture). During 97 days, there were no significant differences in the longevities of the cultures (50% mortality: day 52 in DP -- LD; day 58 in LD). The survival curve of each was almost linear, which is rather unusual in animals. If the regression line, representing each survival curve was linearly extrapolated beyond day 97 (end of experiment), a theoretical maximal life span of 121 days was found for the LD culture, and of 110 days for the DP - LD culture. Beetles did not enter a second diapause as easily as the first. The haemolymph protein pattern of old animals that had ceased reproduction was almost similar to that of young reproducing animals. In both cultures, the last egg was laid at day 86. Mated females produced 30-60 eggs per day as compared with virgin females which produced less than ten per day. Application of JH 1, 20- hydroxyecdysone, prostaglandin E₂, haemolymph or brain extracts of females did not increase egg production in virgins.
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