Temperature Perception

This is the least understood of insect senses. Insects clearly respond to temperature in a behavioral sense, by seeking out a "preferred" temperature. For example, outside its preferred range, the desert locust, Schistocerca gregaria, becomes active. This locomotor activity is random but may take the insect away from the unfavorable conditions. Within the preferred range, the insect remains relatively inactive. Under field conditions, the locust will alter its orientation to the sun, raise or lower its body relative to the ground, or climb vegetation in order to keep its body temperature in the preferred range.

Parasitic insects such as Rhodnius, Cimex, and mosquitoes, which feed on mammalian 389

blood, are able to orient to a heat source. Though the ability to sense heat is present over

^ u ^ f + • U! A . • • + A! 1 SENSORY SYSTEMS

the entire body surface, it appears that in bloodsucking species, the antennae and/or legs are especially sensitive and probably carry specialized sensilla in the form of thick-walled hairs (Davis and Sokolove, 1975; Reinouts van Haga and Mitchell, 1975). In other species aporous, thin-walled, non-articulated hairs or pegs are both thermo- and hygroreceptive

(Figure 12.10), containing at least two neurons. Occasionally, the hairs are socketed and serve also as mechanosensors. The transduction mechanism for thermoreceptors remains unclear. Encoding, however, seems to be relatively simple, with greater numbers of action potentials generated at higher temperatures, and vice versa.

Some insects, including Rhodnius and some fire beetles (Buprestidae), have infrared-sensitive sensilla that enable them to locate a heat source (Schmitz et al., 2000, 2001). In the buprestid Melanophila acuminata each of the paired infrared organs, containing 50-100 sensilla, is located in a pit adjacent to the metathoracic coxae. The sensilla broadly resemble mechanosensilla; that is, they are innervated by a single neuron and are poreless. However, a unique feature is a thin cuticular lenslike structure thought to be where infrared radiation is focused. The dendrites of the neuron terminate immediately below this structure (Vondran et al., 1995). In another buprestid, Merimna atrata, there are two pairs of ventral abdominal infrared organs. The dominant feature of the organ is a large multipolar sensory neuron whose dendrites reach two chordotonal organs in addition to the thermosensitive structure (Schmitz et al., 2001). How the encoded messages from the two sensory inputs are distinguished is unclear.

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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