THE EFFECTS OF RADIATION ON THE HABITAT TEMPERATURES OF THE LODGEPOLE NEEDLE MINER, RECURVARIA MILLERI BUSCK (GELECHIIDAE: LEPIDOPTERA)

Abstract

The lodgepole needle miner (Recurvaria, milleri Busck) passes the greater part of its life in the interior of needles of its host tree. Investigations of the temperature of needle mines and its relation to ambient air temperature, radiation, and a number of other weather factors are reported. Incoming solar radiation shows a heating effect on the needle mines which is directly proportional to the radiation level. The heating effect of the radiation is modified by other weather factors, by differences in the exposure of the needles, and by the type of mines in the needles. At night, needles are cooled below ambient air temperatures by outgoing radiation, which in turn is dependent on the nocturnal weather. The application of these results to studies of the effect of temperature on the needle miner can only be made with respect to individual needles. Thus, radiation of 1.5 gm-cal. per cm.2 per min. will elevate the temperature of a needle 6.3 Centigrade degrees in air moving at less than one mile per hour if the needle is orientated at right angles to the sun and fully exposed. Shade from other needles, wind over one mile per hour, and needle orientation other than 90° to the sun's rays all tend to reduce the amount of heating at the indicated level of radiation.