574 the genitalia or the presence of a spermatophore in the bursa results in information being sent to the brain via the ventral nerve cord, followed by activation of the corpora allata. In representatives of many insect orders male accessory gland secretions are transferred to the female during mating. These chemicals, which move to a range of sites within the female's body (Lay et al., 2004), may serve either as signals, triggering subsequent steps in the reproductive process, or as nutrient contributions enabling females to produce more eggs. For example, in Drosophila, many species of mosquitoes, and some Lepidoptera peptidic materials from the male accessory glands stimulate egg development. Thus, in Drosophila one of the actions of the so-called "sex peptide" is to promote juvenile hormone synthesis and hence increased vitellogenesis (Wolfner, 1997, 2002; Kubli, 2003). In tettigoniids, some butterflies, and Photinus fireflies the spermatophore, either eaten or digested within the reproductive tract, provides nutrients that increase the number of eggs produced (see also Section 4.3.1) (Boggs, 1995; Gwynne, 2001, Rooney and Lewis, 2002).

Like all metabolic processes, egg development is affected by temperature and occurs at the maximum rate at a specific, optimum temperature, whose value presumably reflects the normal temperature conditions experienced by a species during reproduction. On each side of this optimum egg maturation is decreased, in the normal temperature-dependent manner of enzymatically controlled reactions. Sometimes superimposed on this basic effect, however, are more subtle effects of temperature, of both a direct and an indirect nature. For example, in Locusta migratoria regular temperature fluctuations (provided these are not too extreme) appear to stress the insect, causing release of neurosecretion and enhanced rates of development. In some other species mating occurs only within a certain temperature range, yet, as noted earlier, may have an important influence on egg development. It follows that, in this situation, temperature can have an important indirect effect on maturation.

Few direct observations have been made on the effects of humidity on egg maturation, though it is known that humidity may determine whether or not oviposition occurs. In many species eggs are laid only when the relative humidity is high (80% to 90%), and oviposition is increasingly retarded as the environment becomes drier. Engelmann (1970) suggested a possible explanation for this is that, as increasing amounts of water are lost from the body by evaporation, insufficient remains for use in egg development whose rate is therefore decreased.

Photoperiod, the earth's naturally recurring alternation of light and darkness, is probably the best-studied environmental factor that influences egg maturation. The effect of photoperiod is long-term (seasonal) and serves to correlate egg development with the availability of food, suitable egg-laying conditions, and/or suitable conditions for the eventual development of the larvae. Implicit in this statement is the idea that an insect, by having its reproductive activity seasonal in nature, is able to overcome adverse environmental conditions. Commonly, an insect survives these adverse conditions by entering a specific physiological condition known as diapause, whose onset and termination are induced by changes in daylength (sometimes acting in conjunction with temperature). (For a general discussion of diapause, see Chapter 22, Section 3.2.3.) Essentially diapause is a phase of arrested development, and, in the context of adult (reproductive) diapause, this means that the eggs do not mature. In different species diapause may be induced by increasing day length (number of hours of light in a 24-hour period), which enables an insect to overcome hot and/or dry summer conditions (estivation), or by decreasing day length prior to the onset of cold winter conditions (hibernation).

For example, in the Egyptian tree locust, Anacridium aegyptium, reproductive diapause is induced by the decreasing day lengths experienced in fall and is maintained for about

4 months during which no eggs are produced. Termination of diapause, brought about by 575

increasing day lengths in spring, is correlated with renewed availability of oviposition sites

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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