摘要:

Water vapor flux density ofBrachycorynella asparagi(Mordvilko) eggs at 3.3 and 1.1°C increased with water vapor density deficit although the flux decreased over time of exposure. Weight change of the eggs due to net water loss from the surface of the eggs was inversely related to vapor density deficit days (=vapor density deficit × days of exposure). Apparent vapor diffusion resistance of the eggs increased with vapor density deficit days. It appears that as the eggs dried out, the egg matric water potential decreased resulting in a slower rate of water loss. There is some evidence that the eggs absorbed water from the air. The LE50for egg mortality due to desiccation was 192.3 vapor density deficit days. Hatching time and longevity of first-instar fundatrices that were not exposed to additional desiccation were not related to exposure of the eggs to different humidities.

ISSN:1754-5692    

DOI:10.1093/ee/15.4.989

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

Pteromalus puparum(L.) parasitized 64.1 and 32.5% of imported cabbageworm,Artogeia rapae(L.), pupae collected from pesticide-free cabbage field plots in 1983 and 1984, respectively, in southwestern Virginia. Parasitism was most pronounced in the latter part of the season. In commercial cabbage fields, 67.2% of overwintering pupae were parasitized. High percentages of parasites successfully emerged as adults, indicating efficient host utilization. Most parasite mortality within the host occurred in the larval stage; mean adult parasite emergence per host for 1983 and 1984 was 52.3, with a 1:1 sex ratio. However, variability of male parasites per host was double that of females. Females weighed twice as much as males, suggesting a compensation of number for size.P. puparumdid not parasitize either host sex discriminately, and equal numbers of male and female parasites emerged from both host sexes. Laboratory studies suggest that host/parasite ratios and length of host/parasite exposure time are important considerations for laboratory rearing ofP. puparum. Suboptimal conditions result in unparasitized and mutilated hosts.

ISSN:1754-5692    

DOI:10.1093/ee/15.4.994

出版商:Oxford University Press    

年代:1986

数据来源: OUP