干旱区生态环境知识资源中心

The habitat choice and population structure of Heterogamisca chopardi were studied in a middle altitude desert of Saudi Arabia (30 km east of Taif) during June 1992. Two populations were compared, located, respectively, in a 3-year-old protected area and in a grazed area. Cockroaches live in the sand beneath shrubs. They preferred shrub species according to their cushion form, possibly depending on grazing pressure. Population densities ranged between 0.25 and 0.42 individuals per m(2). Most individuals in June were middle-instar nymphs, with few first-instar nymphs and old females. Oothecae were frequently parasitized by Aies (Bombyliidae). In comparison with the protected area, the grazed area showed higher density, the presence of younger middle-instar nymphs and of old females, higher fecundity, larger oothecae, a sex ratio less biased towards females, and probably lower nymphal survival. (C) 1995 Academic Press Limited