Sensory Systems

blue-green (65% yellow + 35% blue-violet)

FIGURE 12.14. Color vision. (A) Fused rhabdom of worker honey bee showing that individual rhabdomeres (1-8) are sensitive to specific wavelengths [ultraviolet (UV), blue (B), or green (G)]. The orientation of the microvilli in each rhabdomere is indicated by the dark bars; and (B) color triangle for worker honey bee. Each corner corresponds approximately to the three wavelengths of maximum sensitivity. Along the base line and right side of the triangle, the color perceived is a function of the relative distance between the corners. Along the left side, the mixture is non-spectral bee purple. The hatched lines connect complementary colors that, mixed in the correct proportions, appear white because the three receptor systems are stimulated equally. [A, after R. Wehner and G. D. Bernard, 1980, Intracellular optical physiology of the bee's eye. II. PolarizationaI sensitivity, J. Comp. Physiol. 137:205-214. B, after K. Daumer, 1956, Reizmetrische Untersuchung des Farbensehens der Bienen, Z. Vgl. Physiol. 38:413-478. By permission of Springer-Verlag.]

to discriminate between colors at low light intensity though, unlike eyes of vertebrates with their rods and cones, the compound eyes of insects do not have different receptors for color and dimlight vision. An exception to this generalization are nocturnal hawkmoths which are important pollinators in tropical forests. Typically, the flowers pollinated by these moths are white (to the human eye), yet in contrast to diurnal white flowers they lack UV-reflecting patterns. Laboratory experiments with Manduca sexta showed that this species is attracted only to artificial flowers reflecting wavelengths greater than 400 nm, specifically in the violet and green parts of the spectrum; indeed, UV-reflecting surfaces were avoided (White et al., 1994). Clearly, the visual system of nocturnal hawkmoths is able to discriminate colors at very low light intensities.

7.1.4. Sensitivity to Polarized Light

As light waves travel from their source, they oscillate sinusoidally about their longitudinal axis. The planes in which they oscillate are usually scattered randomly, through 360°, around the longitudinal axis, but under certain circumstances more waves may travel in a specific plane and the light is said to be polarized. Sunlight entering the earth's atmosphere is filtered, that is, light rays in certain planes are reflected by dust particles, etc., and the light striking the earth's surface is therefore partially polarized. Many insects, including bees, ants, crickets, locusts and some beetles, can detect and make use of the plane of polarization for navigation and orientation. The classic studies of von Frisch and his students (see von Frisch, 1967; Dyer, 2002) showed that foraging honey bees "measure" the angle between a food source, the hive, and the sun and, on returning to the hive, communicate this information to their fellows through the performance of a "waggle dance" on the honeycomb. Actual sight of the sun is not essential for the "light compass reaction," provided that a bee can see a patch of blue sky and thus determine the plane of polarized light.

Beekeeping for Beginners

Beekeeping for Beginners

The information in this book is useful to anyone wanting to start beekeeping as a hobby or a business. It was written for beginners. Those who have never looked into beekeeping, may not understand the meaning of the terminology used by people in the industry. We have tried to overcome the problem by giving explanations. We want you to be able to use this book as a guide in to beekeeping.

Get My Free Ebook

Post a comment