ISSN: 2639-216X
Authors: Ramadan MM* and Ramadan HM
Seasonal fluctuation in relative abundance of the diving beetles (Coleoptera: Dytiscidae) was investigated at Al-Hassa Oasis, Eastern Province of Saudi Arabia, using a 200-Watt Robinson light trap. The trap was placed 1.5 m above ground at the water pump station of the Irrigation and Drainage Project and was operated daily from sunset to sunrise during October 1977 until the end of September 1978. Ground water pumped from wells poured into open concreate irrigation channels are the aquatic basis to agriculture, mainly date palm plantations. From this permanent water source, thirteen species of Dytiscidae were trapped and counted. Only four beetles were properly identified to species (i.e., Hygrotis musicus, Rhantus suturalis, Hyphydrus pictus, Copelatus pulchellus) and their weekly numbers were determined. No significant differences between trap catch assessment of the four species during the year (P>0.05). Hygrotus musicus represented the highest catch per year (46.4%) with a mean ± SEM of 14.5 ± 8.9 beetles per month. Distributional pattern of 1928 adults caught in trap during the year represented a peak of summer upsurge and significant declines during winter-fall seasons. Overall mean beetle catch per week was 40.2 ± 8.5 beetles. This trend reflects on their favorite prey of mosquitoes that decrease during summer at Al-Hassa. Compiled records of Dytiscidae of the Arabian Peninsula including Al-Hassa species are reviewed. Result of this historical investigation can be a useful indicator of biodiversity, for monitoring water quality, and other environmental concerns of a desert oasis.
Keywords: Dytiscidae; Al-Hassa Oasis; Saudi Arabia; Light trapping; Copelatus pulchellus; Hyphydrus pictus; Hygrotis musicus; Rhantus suturalis
