400 successfully return to the nest after foraging (Fent and Wehner, 1985). Similarly, the escape reaction of the bloodsucking bug Triatoma infestans is induced equally well by stimulation of either the ocelli or the compound eyes (Lazzari et al., 1998). In both these examples, it could be the two photosensors are responding to different qualities of the light stimulus (e.g., wavelength and intensity).

Stemmata. These are of three types: (1) In sawfly and beetle larvae each stemma, one on either side of the head, resembles a dorsal ocellus, that is, comprises a single cuticular lens lying beneath which are groups of photosensitive cells with a central rhabdom. (2) In larvae of Neuroptera, Trichoptera, and Lepidoptera, there are usually several laterally placed stemmata on each side of the head. Each resembles an ommatidium in that it includes both a corneal and crystalline lens and a group of retinal cells with a central rhabdom (Figure 12.16B). (3) Finally, in larvae of cyclorrhaph Diptera there are no external signs of stemmata, but a pocket of photosensitive cells occurs on each side of the pharyngeal skeleton.

Stemmata of beetle larvae and caterpillars have been best studied, and their functions appear very similar to those of compound eyes. They form a relatively focused image and are important in color vision, predator avoidance, prey capture, etc. They can also detect the plane of polarized light, though no functional significance has yet been attached to this ability. Indeed, Land (1985) raised the fascinating question of why stemmata ever came to be replaced by the structurally more complex compound eye in the adult stage.

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.

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