The Dominant True Spiders in Seed Watermelon Plantations, and Efficiency of Traps in Collecting Occurring Species

Abstract

Seed watermelon, Citrulus lanatus (Thumb) is an early summer crop, which is a subject to infestations by several insect pests resulting in damage and losses in the crop production. A study was undertaken at Rasheed region, Beheira Governorate during 2015 and 2016 summer seasons to detect the true spider species occurring in seed watermelon plantations, and monitor the population fluctuation of the most dominant ones. In addition, a comparison study was conducted to find out the efficiency of traps, used in spider catch, as related with spider species. Six true spider species were surveyed beginning from first of May up to mid-July. Paradosa sp. and Lycosa sp. (Fam. Lycosidae) and Thanatus albini (Fam. Philodromidae) were captured throughout the season; May to July. On the other hand, Clubiona sp. (Fam. Clubionidae), Singa sp. (Fam. Araneidae) and Thomisus sp. (Fam. Thomisidae) were trapped only during July. The most dominant spider species in 2015 season was Thanatus albini (43.77%), followed by Pardsoa sp. (42.64%), and then Lycosa sp. (4.91%). A reverse situation was found in 2016 season, as the most dominant spider was Pardosa sp. (45.14%), followed by Thanatus albini (41.32%) and the third rank was occupied by Lycosa sp. (4.17%). However, the dominance percentages of the remaining spiders ranged between 0.17 and 4.17% in both seasons. Tools used for capturing spiders were variable in their efficiency. Pardosa sp. was captured mainly by pitfall traps, with values of 90.27 and 93.08%, out of total catch of different traps, in the first and second seasons, respectively. Lycosa sp. was not captured by the sweep net, and captured in low numbers by each of pitfall and water pan traps. Thanatus albini was captured by the sweep net (39.66 & 41.86%) and water pan trap (47.41 & 50.39%) in 2015 and 2016 seasons, respectively, but was captured in low numbers in the pitfall traps. Clubiona sp., Singa sp. and Thomisus sp. were all not detected in the pitfall traps, and were found in low numbers in each of sweep net and water pan traps.