Lethal attraction

• Main Authors: Chih-Yuan Chuang, 莊智元
• Other Authors: I-Min Tso
• Format: Others
• Language: en_US
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/62709486377535149797

碩士 === 東海大學 === 生命科學系 === 94 === In this study the importance of the visual interactions between nocturnal predators and their prey was assessed by investigating whether body color of nocturnal orb weaving spiders were attractive to their prey. Neoscona spiders hunt during the night and most parts of their body are inconspicuously brown, which is similar to the color of their diurnal perching sites. However, the ventrum of various species of Neoscona exhibits bright color spots in ventrum and deep red femurs, both are distinct from the brown body. I manipulated the color signals of bright ventrum spots and red femurs to see if such treatments would affect their prey interception rates. In the first part of the study, I used the night shoot mode of video camera to record the prey interception rates of webs with or without N. punctigera. Then I measured the reflectance spectra of various body parts of those spiders and their typical perching sites to assess how these colors were viewed by diurnal and nocturnal insects. Webs with N. punctigera intercepted significantly more insects than those without spiders, indicating that the spiders constituted an attractive signal to nocturnal insect. A comparison of color signals of the spiders and their background using diurnal visual models showed that hymenopteran insects could not distinguish the brown body color of N. punctigera from that of bark. However, the bright ventrum spots of N. punctigrea were highly visible to insects when viewed against the vegetation background. Results of analyzing color signals in the nocturnal context show that spider’ ventrum spots exhibited high color contrasts and were similar to those flowers blossoming during night time. Furthermore, when the color signal of the bright spots was altered by paint, spider’s prey interception rates decreased significantly. Such results demonstrated that bright spots of N. punctigera function as visual lures mimicking the color signals of flowers to attract nocturnal prey.