Oviposition

Oviposition (egg laying) is an extremely important phase in an insect's life history for, unless it is carried out at the correct time and in a suitable location, the chances of the eggs developing and of the larvae reaching adulthood are slim. Except in normally partheno-genetic species, unfertilized eggs are generally inviable, and it is important, therefore, that oviposition occurs only after mating. The eggs when laid must be protected from desiccation and predation. Further, because larvae are relatively immobile, it is necessary to lay eggs close to or even on/in the larva's food. This is especially true when the food is highly specialized and/or in limited supply as, for example, in many parasitic species.

Conversely, it is desirable that the female not expend energy searching for and testing potential oviposition sites until she is ready to lay. Accordingly, oviposition behavior characteristically does not begin until the eggs are more or less mature and may be induced by the hormone balance in the female at this time.

7.1. Site Selection

Only a few examples are known of insects that apparently show no site selection behavior. Phasmids simply release their eggs, which fall among the dead vegetation beneath the host plant, though even this may be adaptive, as the eggs presumably will be hidden and protected from heat, desiccation, and predation. Females of many species attach their eggs, either singly or in batches, to an appropriate surface (often the food source) using secretions of the accessory glands. Such species typically lack an ovipositor. Other insects lay their eggs in crevices, or in plant or animal tissues, typically using an ovipositor formed by modification of either the terminal abdominal segments per se or the appendages of these segments (Chapter 3, Section 5).

The initial location of an egg-laying site may be more or less specific, often depending on rather general visual or chemical stimuli that tend to attract the female. For example, cabbage butterflies (Pieris spp.), which are attracted to blue or yellow objects when sexually immature, show a preference for green when ready to lay. Mosquitoes are attracted to dark or colored waters and to sites where fermenting materials provide olfactory signals. For grasshoppers and locusts, the texture, moisture content, and salt content of the soil are important site-selection cues, detected by sensory receptors at the tip of the abdomen. Many parasitoids are attracted initially to a likely host site by the odor and color of the host's food plant.

The final choice of an oviposition site depends on more specific stimuli. Thus, continuing the examples cited above, Pieris is attracted by the odor of oil of mustard, which is released by cabbage and its relatives. Even then, the female may not lay if she detects the oviposition-deterring pheromone that coats the eggs deposited by a prior female (Schoonhoven, 1990). Culex mosquitoes assess a potential egg-laying site using tarsal

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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