1964 Volume 8 Issue 3 Pages 179-184
1. Microclimatic temperatures of environments such as those of store-, green- or vinylhouses as well as of underground during the winter all of which may serve as a hibernation shelter of either maggots, pupae or flies will alter the judgement a little on the possibility of establishment in the oriental countries hitherto described basing upon the macroclimatic grounds.
2. Outdoors almost no host plants of melon fly are found during the winter of the oriental countries. On the other hand for the oriental fruit fly various kinds of citrus fruits are on the trees. They are however green and hard. Unless they are readily available, the survival is sure to be highly difficult, because the life of the both pests is never longer than 10 days during the midwinter of Japan.
3. The number of individuals actually introduced into northern countries in the past had to be negligibly small. This will hold true also in future. The percentage of mortality sustained by the insects during exposures to the experimental low temperatures as well as during starvation for only a short period is always exceedingly high.
4. The general conclusions we arrived at finally are as follows:
Eggs, maggots and pupae each may be able to live and develop to the adult stage and the flies may reach maturity and oviposit with success during the warm seasons extending from spring to autumn in the temperate countries. But they will be unable to survive the winter cold in their preimaginal periods in these areas excluding Ryukyu Arch., Ogasawara Is. and Izu Is. If food is unavailable, the same may hold equally good in the case of adults. If there is a sequence of favorite hosts, the overwintering of the adult flies may not be always impossible in the west-southern half of Japan. The facts that the insects exposed experimentally to the winter low temperatures of the temperate climate always suffer a significantly high mortality and that the chances of spread and the individuals that could reach successfully, have been neither frequent nor large in numbers will tell why they have never become established in those countries. We suppose that this may be true also in future.
