Jurnal Biosains, 18(1), 81–91, 2007 THE SEASONAL ABUNDANCE OF SYNANTHROPIC FLY POPULATIONS IN TWO SELECTED FOOD OUTLETS IN PULAU PINANG, MALAYSIA Nurita Abu Tahir, Abu Hassan Ahmad*, Nur Aida Hashim, Norasmah Basari and Che Salmah Md Rawi Medical Entomology Laboratory, School of Biological Sciences, Universiti Sains Malaysia, 11800 USM Pulau Pinang, Malaysia Abstrak: Kajian kelimpahan bermusim lalat sinantrofik dewasa dijalankan dari Julai 2003 sehingga Julai 2004 di sebuah kafeteria di kampus induk Universiti Sains Malaysia (USM) dan di sebuah restoran di luar kampus. Spesies yang telah dikenal pasti ialah Musca domestica, Musca sorbens, Chrysomya megacephala dan Lucilia cuprina. Restoran di luar kampus mempunyai kelimpahan lalat yang secara signifikannya lebih tinggi (p < 0.05) berbanding kafeteria universiti dengan spesies lalat yang dominan di kedua-dua lokasi ialah M. domestica. Kelimpahan lalat paling tinggi direkodkan di kedua-dua lokasi kajian pada April 2004. Kelimpahan lalat paling rendah di kafeteria universiti dan di restoran luar kampus masing-masing pada Mac 2004 dan Oktober 2003. Abstract: The seasonal abundance study of adult synanthropic flies in two selected food outlets was conducted from July 2003 to July 2004. The two urban locations were a cafeteria in the Universiti Sains Malaysia (USM) main campus and an adjacent restaurant. Four synanthropic flies were identified from both study sites and they were Musca domestica (house fly), Musca sorbens, Chrysomya megacephala and Lucilia cuprina. The off-campus restaurant had a significantly higher (p < 0.05) fly abundance than the university cafeteria and the dominant fly species at both sites was the M. domestica. The highest fly abundance recorded at both sites was in April 2004. Total fly abundance was lowest in the university cafeteria and in the off-campus restaurant in March 2004 and October 2003 respectively. Keywords: Seasonal Abundance, Synanthropic Fly, Food Outlets INTRODUCTION Studies around the world have shown that almost all fly species population, including the house fly, fluctuate even when no control measures are used (Greene 1989). This fluctuation in abundance can be attributed to natural factors such as weather, predators, parasites and diseases (Moon & Meyer 1985). Elements such as humidity, temperature and rainfall can also greatly influence the conditions of breeding sites, the period of oviposition and the feeding habits of adult flies as well as the survival of eggs and larvae (WHO 1986). In the tropics, wet conditions increase the number and size of breeding sites thereby increasing fly population numbers, whereas the opposite is true for dry weather (Bay & Harris 1988). Weather conditions also influence rates of population increase and this in turn influences the number of flies available for trapping (Wall et al. 1992, 1993; Wardhaugh et al. 1994). In Papua New Guinea and Iraq, *Corresponding author: aahassan@usm.my 81