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590 sensilla that determine water quality (salinity, pH, and amount and type of organic matter present). Oviposition-aggregation pheromone released from previously deposited egg rafts may also be an important oviposition cue (McCall, 2002). Likewise, the egg-pod froth (Section 7.3) of desert locusts releases an aggregation pheromone that attracts conspecific females to a common oviposition site (Saini et al., 1995). Having located suitable host habitat, parasitoids seek out a potential host using an array of sensory cues: sight, touch, smell, and taste. Once a potential host is found, the female may probe it with her ovipositor. In this way she recognizes the host and, moreover, determines whether or not it is already parasitized (Steidle and van Loon, 2002).

7.2. Mechanics and Control of Oviposition

Compared to ovulation, oviposition is much more complex in terms of both its mechanics and its regulation, the latter being influenced by both internal and external variables as outlined in Section 7.1. Expulsion of eggs via the genital pore results from rhythmic peristaltic contractions of the walls of the oviducts. Concurrently, muscles may move the ovipositor, where present, so that a suitable egg-laying cavity is formed, and sensory input from mechanoreceptors on the ovipositor may be important where precise positioning of eggs in the substrate is required. Removal of the terminal abdominal ganglion or section of the ventral nerve cord anterior to the ganglion has demonstrated the importance of neural control in many species. In other species myotropic (oviposition-stimulating) hormones and/or pheromones may also be involved. Where ovulation is followed immediately by oviposition, as in Rhodnius, it seems likely that the ovulation-inducing hormone will also trigger peristalsis of the oviduct muscles. And there is evidence from species with temporally separated ovulation and oviposition (e.g., grasshoppers and locusts) for the production, by median neurosecretory cells, of a myotropic hormone. The action of this hormone is to enhance the frequency and amplitude of contractions of the oviducal muscles.

Release of a myotropic hormone or initiation of motor impulses in species where egg laying is controlled neurally depends on sensory input received by the central nervous system, and examples were given above of chemical and physical information on the oviposition site acquired in this way. However, another important consideration for a gravid female is whether or not she has been inseminated, since, as noted above, unfertilized eggs are normally inviable. In some insects, such as the cockroaches Pycnoscelus and Leucophaea, filling the spermatheca with semen stimulates neural pathways that terminate in the muscles used in oviposition. In Rhodnius filling the spermatheca causes this structure to release a hormone that, directly or indirectly, triggers oviposition. In a number of Diptera and Orthoptera, and other insects, there is evidence that semen contains a pheromone (fecundity-enhancing substance) that stimulates release of a myotropic hormone by the brain (Gillott and Friedel, 1977; Gillott, 2003).

7.3. Oothecae

Many orthopteroid insects, for example, locusts and grasshoppers, mantids, and cockroaches, surround their eggs, which are laid in batches, with a protective coat, the ootheca. The ootheca is produced from protein secretions of the accessory glands that are tanned in a manner similar to those of the exocuticle (Chapter 11, Section 3.3). The resulting structure is thought to prevent desiccation and, perhaps, parasitism. The egg pod of Acrididae consists of eggs surrounded by a hard, frothy mass (Figure 19.10A). The egg "cocoon" of

FIGURE 19.10. Oothecae. (A) Egg pod of Acrida (Orthoptera); (B) ootheca of Hierodula (Mantodea); (C) transverse section through ootheca of Hierodula; (D) ootheca of Blattella (Blattodea); and (E) transverse section through crista of Blattella ootheca. [A, after R. F. Chapman and I. A. D. Robertson, 1958, The egg pods of some tropical African grasshoppers, J. Entomol. Soc. South. Afr. 21:85-112.By permission of the Entomological Society of Southern Africa. B, C, after Kershaw, J. C., 1910, The formation of the ootheca of a Chinese mantis, Hierodula saussurii, Psyche 17:136-141. E, after V. B. Wigglesworth, 1965, The Principles of Insect Physiology, 6th ed., Methuen and Co. By permission of the author.]

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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