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710 the edible mimic; that is, the population density of the model must greatly outweigh that of the mimic. Another chemical method of defense is to secrete obnoxious liquid or vapor whose odor repels predators. Other species release poisons that, on contact with skin or when injected by means of spines, hairs, or sting, injure or kill the attacker (Blum, 1981).

Some insects, especially species of butterflies, practice intimidation displays aimed at frightening would-be (vertebrate) predators. The butterflies normally rest with their wings closed vertically above the body. On being disturbed, the butterflies rapidly open their wings to reveal a striking color pattern, often including large "eyespots," intended to evoke prompt retreat of the aggressor.

Predators use a variety of stimuli in order to locate prey. Some may attempt to capture and eat anything that moves within a certain size range and employ only simple visual or mechanical cues for detection of prey. Most species are, however, relatively prey-specific (feed on only a few or a single species of prey), and prey location is therefore a much more elaborate process. For many of these more specialized predators, the first step is location of the prey's habitat, and this is often achieved as a result of attraction to odors released from the food of the prey. For example, females of the ichneumon fly, Itoplectis conquisitor, a parasitoid, are attracted by the odor of pine oil, especially that of Scots pine (Pinus sylvestris), on which one of its preferred hosts, caterpillars of the European pine shoot moth, Rhyacionia buoliana, are found. For some predators, attraction is greater after the food of the prey has been damaged by the prey. The pteromalid Nasonia vitripennis, for example, is attracted to meat, especially when this has been contaminated by the parasitoid's hosts, various muscid flies. Similarly, the ichneumon Nemeritis (= Venturia) canescens is more attracted to oatmeal contaminated by its host, larvae of the Mediterranean flour moth, Ephestia kiihniella, than to clean oatmeal (Vinson, 1975).

Having been attracted to the habitat of its prey, a predator must now specifically locate the prey. For many species this involves a systematic search, though this behavior is initiated only after receipt of an appropriate signal that indicates the likelihood of prey in the immediate area. Again, such signals are usually chemical in nature and include odors from the prey's feces or from the damaged tissues of the prey's food plant. Pheromones released by the host are often used by parasitoids to locate the host (Powell, 1999; Powell and Poppy, 2001; and see Chapter 13, Section 4.2). Final location of prey is commonly achieved by means of its taste, rarely by its odor (effective only over a very short distance). Some parasitoids locate hosts by the vibrations or sounds the latter make as they burrow through the substrate.

In some species, location of prey is followed immediately by feeding or, in parasitoids, oviposition or larviposition. In others, additional stimuli must be received before prey is deemed acceptable. These appear to be especially critical in parasitoids for which selection of hosts of the correct age (judged by size, color, shape, texture, or taste) may by important. For example, some parasitoids accept only hosts above a certain size; cylindrical host shape improved acceptance in the ichneumon Pimpla instigator; hairiness of the host (by preference, caterpillars of the gypsy moth, Lymantria dispar) is an important determinant of acceptability in the braconid Apanteles melanoscelus; and female Itoplectis conquisitor probe host larvae with their ovipositor but will lay eggs only if the host's hemolymph has a suitable taste. Movement may be an important stimulant or deterrent of acceptability. Some parasitoids oviposit only if a larval host moves, whereas movement of an embryo within an egg (indicative of the egg's age) may inhibit oviposition by egg parasitoids (Vinson, 1975, 1976). A special feature of many parasitoids is their ability to discriminate between non-parasitized and parasitized hosts on the basis of physical markings, odors, or tastes

left by the original parasitoid as it oviposited or larviposited. Such marks render a host unacceptable to the parasitoids that locate it subsequently and ensure that the parasitoid larva, on hatching, has sufficient food for its complete development. Other parasitoids leave trail-marking pheromones as they search for hosts, which inhibit researching of an area and thereby facilitate dispersal of the species.

When given a choice a predator may consistently select a particular species for prey. However, in its natural habitat its survival does not normally depend on availability of that species, and in its absence other species are acceptable as prey. Special mention is made of this point, as it has sometimes been overlooked in attempts at biological control of pests. Some attempts have failed because the introduced predator reduced the pest to low density and then died out because alternate prey was not available in the new habitat. As a result, the pest was able to rebound to an economically important level. In other words, secondary prey species form an important reservoir for the predator at times when the density of the primary prey is low.

4.2.3. Insect-Insect Mutualisms

Mutualistic relationships between insects are relatively uncommon, an important exception being that in which some species of ants tend, protect, and sometimes transport to new locations other insects, notably various homopterans (aphids, psyllids, and mem-bracids) and the larvae of many lycaenid butterflies, in return for which the ants feed on fluids produced by their associate. In homopterans the fluid is the honeydew defecated in large amounts through the anus (Figure 23.6); in myrmecophilous lycaenids, however, special "Newcomer's glands" on the dorsum of the seventh abdominal segment produce an enriched sugar solution (Holldobler and Wilson, 1990).

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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