7.1 Prey deception in australian crab spiders

Author: Claire Shorall

Introduction

Have you ever seen an advertisement for a food item that looked so scrumptious you had to have it? A flame-broiled burger, perhaps, with a juicy patty piled with fresh vegetables sandwiched between an artisan-bread bun. And then, once you had raced out of your house to the nearest drive-thru, you find the burger to be dismal -- grayish meat, wilted veggies and tasteless bread; the lure of the image on television instantly unraveled after the first bite. Welcome to the world of false advertisement. Retailers who use this method use exaggerated and calculated imagery to convince consumers to buy their product, ever-so-sure of the negative benefits to their customers. Deceitful advertising is not a human invention, however. Species of ultraviolet (UV)-positive Australian crab spiders Thomisus spectabilis tactfully position themselves on floral surfaces with no or low UV-reflection in order to create the greatest amount of contrast between their body and the flower, a trick that makes the flower more attractive to pollinators such as honeybees (Bhaskara et al. 2009). Once lured to a plant, a crab spider will ambush the honeybee, trapping their prey with their powerful front legs and then paralyzing the unsuspecting pollinator with a venomous bite. But UV-contrast is not the only weapon in their arsenal of deceit. Australian crab spiders can also change their body color from yellow to white in order to attract honeybees to the white or yellow daisy they occupy, however this color change does not follow the logic of normal crypsis (Heiling et al. 2005). Spiders will both attempt to blend into the background, using color as a mechanism of camouflage , and also in some cases create high contrast with their background, a visual marker which proves intriguing to their hymenopteran prey.