The effects of exposure to sub-freezing temperatures on the survival of insects have been studied experimentally mainly in three types of insect. One is the beetles associated with stored products, including Bruchus obtectus (Carter, 1925), and Tribolium confusum (Nagel and Shepard, 1934, and Salt, 1936). A leaf feeding beetle, Popillia japonica (Payne, 1928) has also been studied. The emphasis of these studies has been on the possibility of physical control of these pests. The second type includes the hitch-hikers on aircraft. Knippling and Sullivan (1957) studied the survival of six species of insects and a tick which were exposured to 0, −5, −10, −15, −20, and −30°C. for one hour, and that of one of the insects, the house fly, to −20° for different durations up to 60 minutes. Their objective was to determine the possibility of these arthropods being transported alive by aircraft. Thus, the conditions which they tested were those which may be encountered by the arthropods in the unheated parts of jet aircraft during flights in the stratosphere. The third type of insects is Drosophila, mainly D. melanogaster. Since the present paper deals also with this insect, pertinent facts reported by earlier authors are summarized in Table I.