Intraspecific Larval Competition by the Codling Moth, Laspeyresia ponwllella12

Abstract

The effects of larval competition on rate of development, carrying capacity of an apple, ovarian development, head-capsule width and O 2 uptake were examined for Laspeyresia pomonella (L.). A laboratory strain of codling moth, originating from Yakima, Washington, was used, although it may not be typical of wild populations. Experiments were conducted at 26°±2°C and a 16-hour photoperiod, except that oxygen measurements were carried out under dark conditions. Rate of development decreases at higher competitive levels. The carrying capacity for a 4-cm-diameter apple is approximately three larvae per apple. The mean number of eggs developing per moth is reduced at higher competitive levels. The head-capsule width for second and fourth instars decreases with increased competition. Third and fourth instars have a linear relationship between O 2 uptake and body-weight. There was a reduction in O 2 uptake for competing third instars. Fourth and fifth instars did not show differences in O 2 uptake due to competition. Fifth instars displaced from the competing arena decreased their O 2 uptake. Precompetitive O 2 uptake rates for displaced and nondisplaced larvae were greater than the postcompetitive rates.