- 著者
- Tanaka,Kazuhiro
- 出版者
- Zoological Society of Japan
- 雑誌
- Zoological science
- 巻号頁・発行日
- vol.14, no.5, 1997-10
Cold tolerance of overwintering nymphs of a cockroach, Periplaneta japonica, was examined in terms of the supercooling capacity and lower lethal temperature. The supercooling point of overwintering nymphs fell in a relatively narrow range of temperature from -6 to -9℃ and no correlation was observed between the supercooling point and body size. In the temperature range from -5 to -8℃, a significant proportion of cockroaches could tolerate a 12 hr period of tissue freezing. The freeze tolerance capacity differed between nymphal instars, but the supercooling capacity was similar for all nymphs. In a freezing trial at -6 and -7℃, none of the first instar nymphs recovered after tissue freezing, whereas many mid (from 3rd to 5th) and final (8th) instar nymphs survived freezing. Glucose, myo-inositol, scyllo-inositol and trehalose were found in overwintering nymphs, but neither the array nor the content except for trehalose differed among the nymphal instars. Unexpectedly, the concentration of trehalose was negatively correlated to freeze tolerance. Winter survival of this cockroach may be based on both the freeze tolerance and microhabitat selection.
- 著者
- TANAKA,Kazuhiro
- 出版者
- 東京昆蟲學會
- 雑誌
- 昆蟲
- 巻号頁・発行日
- vol.57, no.4, 1989-12-25
Seasonal food supply for the house spider, Achaearanea tepidariorum, was investigated from 1985 to 1986 on the campus of Hirosaki University, Aomori Prefecture. A total of 1490 animals caught by the spider were collected in the two years census and classified into 15 orders of arthropods, in which wingless animals predominated. The abundance of the wingless animals in the diets might be due to the web structure of this spider. Though the spiders fed at any time, more than half of the prey items were captured during the daytime (6 : 00-18 : 00). The seasonal food supply as inferred from the rate of predation shows an unimodal pattern with a peak in July. The result corresponded well with the seasonal trend of the number of possible prey animals collected by sticky traps in the same field. As this spider continues to reproduce over a long period of time, its nymphal development should be considerably affected by the seasonal food supply.