Head capsule widths and the rate of development of the instars of codling moth, Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae)
Head capsule widths of the instars of codling moth, Cydia pomonella (Linnaeus), a severe cosmopolitan pest of apples, were measured for laboratory-reared larvae and two cohorts of field-reared larvae. At the same time the accumulated degree days to reach the various instars was estimated. The results show that there were always five distinct instars. By measuring the head capsule width of larvae found inside infested apples and using the degree day data, pest managers can determine the instar, larvae age, and therefore when the fruit was entered. This information may give important clues towards understanding the reasons for control failure.