Biological studies on the Hawaiian beet webworm, Hymenia recurvalis were carried out under laboratory conditions of 18.6 ± 2°C and 70 ± 5% R. H. The incubation period ranged between 5 and 7 days with a mean of 6.0 ± 0.3 days. The mean durations of larval, prepupal and pupal stages were 26.29 ± 0.3, 5.04 ± 0.08 and 16.86 ± 0.18 days, respectively. Mean adult longevities were 28.42 ± 1.80 and 26.08 ± 1.83 days, ranging between 19-41 and 15-37 days for female and male, respectively. The sex ratio was about 1 : 1.3 (♀ : ♂ ). Accumulative thermal units needed for certain biological features of H. recuurvalis were calculated and the estimated thermal thresholds were 10.97, 12.14, 10.49 and 13.55°C for egg, larval, pre – pupal and pupal stages, respectively. The corresponding values for the thermal units needed for development of these stages were 51.49, 168.47, 47.88 and 102.59 day degree at 25°C for the respective stages.

The present study was carried out in the desert valley (wadi) Abu Salam (63 Km.) east of Berber city, RiverNileState, and in the nursery of the Faculty of Agriculture, NileValleyUniversity. The autecology and biology of major desert specie, Handal (Citrullus coloynthsis), were studied. The study area (Wadi Abu Salam) was divided into three sections; upper, middle and lower. The soil was classified as sodic soil and contained a high percentage of clay in the upper section, equal percentage of clay and sand in the middle section and high percentage of sand in the lower section. The distribution of Handal plant in the wadi area was investigated. In the first season, it was only detected in the middle section (0.60-0.72 plants/m2). In the second season, the plant was distributed in the three sections of the wadi (1.46-1.66 plants/m2 for the upper section, 0.27-0.49 plants/m2 for the middle section and 0.3-0.4 plants/m2 for the lower sections).The rate of photosynthesis increased during the first stage of growth to reach its maximum (2.2-2.34 gm/day) during the 8th week from the start of germination, then started to decline till it reached its minimum rate (0.10-0.12 gm/day) at the maturity stage in both seasons. Plant roots growth started at a low rate, then, increased with plant development and became equal after 7 weeks from germination. After that, it decreased until it reached its lowest rate at the stage of maturity.