Four piercing-sucking insects whiteflies, Bemisia spp., thrips, Thrips spp., leafhopper, Emposca spp. and aphids, Myzus persica & Aphis gossypii, were monitored on cucurbit plants (cucumber, squash, melon and watermelon) during May and June, 1999. Sticky traps were placed at the plant height in fields of three districts, Al-Hasa, Qatif and Riyadh. Data showed that the mean number of whiteflies/trap was higher in Al-Hasa district when compared with that of Qatif and / or Riyadh. Moreover, whiteflies population was abundant in May than that in June at Al-Hasa and Qatif  fields, while very small number of adults was captured on traps in May at Riyadh. Same trend of thrips number was observed, whereas Al-Hasa district had the highest number in both inspection months. In the meantime, thrips population was more in May compared with that of June. The mean number of leafhopper /trap was higher in Riyadh followed by Al-Hasa and Qatif and the prevalence of leafhopper population was more in May compared with that in June. However, the mean number of aphids/trap was higher in Riyadh followed by Qatif and Al-Hasa. The frequency of insects in descending order was as follows: whiteflies, thrips, leafhopper and aphids.