Glp

584 influences may also be important. For many species an obvious correlation exists between receptivity and state of egg development in virgin females, and it appears that the level of circulating JH governs receptivity. Many females mate only once or a few times, and after mating become unreceptive to males for a varied length of time. The switching off of receptivity has been related to the presence of semen in the spermatheca. In some species it appears that stretching of the spermathecal wall may lead to nervous inhibition of receptivity. In others, inhibition is pheromonal, the seminal fluid containing a "receptivity-inhibiting" substance that either directly, or by causing the spermatheca to liberate a hormone into the hemolymph, acts on the brain to render the female unreceptive (Gillott, 1988, 2003; Wolfner, 1997).

In many species, mating occurs only at a certain time of the day. For example, certain fruit flies (Dacus spp.) mate only when the light intensity is decreasing. Other species have built-in circadian rhythms of mating.

Some Lepidoptera mate only in the vicinity of the larval food plant, the odor of the plant stimulating release of sex attractant by the female.

During copulation, some of the behavioral elements introduced during courtship may be continued, presumably to keep the female pacified until insemination is completed. Sometimes pacification continues after insemination and is thought to prevent the female from ejecting or eating the spermatophore until the sperm have migrated from it.

4.3.1. Insemination

Insemination is the transfer from male to female of sperm and seminal fluid. Although the latter has some obvious functions such as the protection of sperm and the provision of a nourishing fluid in which the sperm can be moved to their site of storage, it also contains chemicals that may modulate the female's postcopulatory behavior and physiology to the male's advantage.

As noted earlier, indirect sperm transfer occurs in some apterygotes, but in almost all Pterygota, sperm is transferred during copulation directly to the female reproductive tract. Primitively, sperm are enclosed in a special structure, a spermatophore, which may be formed some time before copulation (in Gryllidae and Tettigoniidae) or, more often, as copulation proceeds. Spermatophores are not produced by males of many species of endopterygotes, especially higher Diptera, or by some male Hemiptera; rather, the semen is transferred to the spermatheca via an intromittent organ.

Spermatophore Production. Production of a spermatophore has been studied in relatively few species, and it is difficult, therefore, to generalize. Essentially, however, the structure is formed by secretions of the accessory glands and sometimes also the ejaculatory duct. The secretions from different gland components may mix or remain separate, so that the wall of the spermatophore is formed of a series of layers surrounding a central mass of sperm. In most katydids and some other Ensifera the spermatophore comprises a sperm-containing sac and a large sperm-free mass (spermatophylax) that is eaten by the female after copulation (see below).

Gerber (1970) proposed four general methods of spermatophore formation, which form a distinct evolutionary series. In the most primitive method (first male-determined method), found in many orthopteroid species, the spermatophore is complex and formed either at the anterior end of the ejaculatory duct or within the male copulatory organ. After transfer to a female, the spermatophore is usually held between her external genital plates and only its anterior, tubelike portion enters the vagina or bursa. In the second male-determined method, the spermatophore has a less complex structure and is formed within a special sper- 585

matophore sac of the copulatory organ. The thin-walled sac is everted into the bursa, which

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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