在動物界中，鮮豔的體色代表了生物個體的獨特訊號，而這類的訊號具有非常多樣化的功能，也能反映出個體的生理狀態；為了能在被掠食者發現時轉移注意力並有機會脫離，次級防禦策略也常常存在於許多動物的構造或行為。像是身體有著大而鮮豔的色斑以及形態或行為突然改變，這些能使掠食者產生遲疑或錯愕的防禦機制往往會讓掠食者另尋目標。許多日行性及夜行性結圓網的蜘蛛，身體腹面具有鮮豔的色斑，可用來吸引飛行性昆蟲。不同於在開放空間結圓網及利用腹面色斑吸引獵物的結網蜘蛛，裂腹蛛(Herennia multipuncta)則是棲息在樹幹表面，其頭胸部的背面帶有橘色環狀色斑，腹部的背面為灰褐色，且間雜黑褐色的點狀斑紋；腹部的腹面則為鮮艷的橙紅色。平時蜘蛛會棲息在梯形網上半部一個由絲所織成的凹陷圓盤中，將其鮮豔腹面平貼在樹幹表皮。我認為裂腹蛛其頭胸部橘色環狀色斑的背面帶具有誘引獵物的功能，而其橙紅色腹面之功能可能是用來進行威嚇行為使掠食者產生錯愕而得以逃脫。為了測試這兩種假說，首先我先挑選與裂腹蛛體色相近的色紙並製作成蜘蛛模型，在野外利用攝影機觀察蜘蛛模型與獵物及捕食者的互動事件。為了測試捕食者防禦假說，我選擇斯文豪氏攀蜥作為掠食者的角色，利用攝影機拍攝裂腹蛛與攀蜥之互動狀況，藉由黑色塗料操控其腹面體色而探討其是否有提昇威嚇天敵之效果。結果顯示，有無橘色環狀色斑對於蜘蛛誘引獵物的功能在白天及晚上有顯著的影響，背部有無灰色區塊則在晚上對於誘引獵物有顯著的影響。而測試捕食者防禦之實驗結果顯示，蜥蜴會花較長之時間注視腹面紅斑未被塗黑之個體，也會在等待較長的時間後再次接近蜘蛛。這些結果說明了裂腹蛛的腹面與背面體色同時具有不同的功能，分別用於誘引獵物及防禦自身提昇存活率。 In the animal kingdom, conspicuous colouration may serve as a unique signal, exhibit diverse functions and is condition dependence. In order to escape with little or no damage, many animals have colors and behaviors that can divert a predator′s attention. The aforementioned adaptations are classified as secondary defense mechanism and they may cause a predator to search for a less challenging meal. Comparing to other diurnal and nocturnal web spiders building aerial orb webs and attracting prey visually with conspicuous body colors, Herennia spiders place the ladder web against the tree trunk with dorsum exposed and conspicuous ventrum concealed. The dorsal side of Herennia is dark gray with black spots and orange circular bands, while the ventral side is brightly orange. I hypothesize that the dorsal orange circular bands of Herennia spiders may function to visually attract prey, and the ventrum orange spot may function to startle or intimidate predators. I used digital video cameras to record responses of prey to Herennia multipuncta dummies with or without orange bands day and night. In addition, I manipulated the colors of this spider’s conspicuous ventrum to evaluate if such body color functioned to startle the predators. Results showed that the orange circular bands in dorsum could enhance the prey attraction rate during diurnal and nocturnal periods significantly, while the gray patch on the dorsum only enhanced the prey attraction rate during nocturnal period significantly. I also found that lizards would spend more time watching Herennia multipuncta with an orange ventrum and exhibit higher latency to approach or attack such spiders. Results of my studies thus show for the first time that an organism enhances foraging success and survival by color signals of different body parts expressed in different circumstnces.
