Factors Affecting Predators And Prey

The predator—prey equation is never constant. Age and size of respective predator and prey, hunger levels, population sizes, presence of alternative prey, and behavioral factors are ever changing. Size of a potential predator relative to prey size is an obvious factor affecting defensive capabilities of an insect. For example, an ant's mandibles might be an effective defense against a small jumping spider, but likely are ineffective against an anteater. Hunger is an important, often overlooked, factor in the defensive equation. Investigators sometimes starve a potential predator for a period of time to ensure that it is hungry when presented with a potential prey. This often yields false impressions, because a starved predator is much more likely to try to attack almost anything that might be edible than would a well-fed predator. An analogy from human experience is instructive. Humans faced with starvation from war or other disasters have eaten rats or cockroaches in an effort to survive, but these same people would not consider such items when not starving. The effect of predator hunger can greatly affect the success of insect defenses. Hunger level can also affect prey insects by inducing them to forage for food during more dangerous times and for longer periods.

Population levels also influence the success of insect defenses. Cryptic (concealed) caterpillars (Figs. 1 and 2) are at more risk of failure of their defensive concealment when high populations of paper wasps (Polistes) are present than at times of low wasp numbers. The opposite situation, high populations of prey, can turn the defensive tables in favor of the prey. The synchronous emergence of periodic cicadas and mayflies not only serves reproductive benefit but also saturates the predators in the environment, reducing the risk to each individual cicada or mayfly. Presence or absence of

FIGURE 1 Looper caterpillar (Geometridae) with fleshy body projections whose shape and appearance closely match the vegetation of its host plant, Polygonella sp., providing excellent camouflage and protection from visually searching predators. (Author photograph, Florida, U.S.A.)
FIGURE 2 Second instar of Eumorpha typhon cryptically matching background grape leaf as it rests. (Author photograph, Arizona, U.S.A.)

alternative prey affects the success of various insect defenses. Some species of caterpillars exhibit several different color patterns. These color differences form the basis for "apostatic selection," which confers protective benefit on the rare color morph (form). The rarer morph is safer because birds adopt search images or searching behaviors oriented toward discovery of the common-color morph and often miss rare-color morphs that do not fit the image. Predator behavioral factors can determine the effectiveness of the defensive behavior of prey. Prey speed and flight ability often provide excellent protection from predators that actively search for prey. Flies and bees rarely fall prey to roving spiders, but often are captured by ambush sit-and-wait crab spiders. In the examples of vinegaroons (whiptail scorpions, Mastigo-proctus giganteus) and tarantula spiders, which are classical ambush predators, fast and powerful prey such as sulpugids (wind scorpions) and centipedes are surprised by the ambush predator and fall prey. The element of surprise is crucial. Without surprise, the powerful jaws and quickness of alert sulpugids and centipedes make them formidable prey that would be difficult, if not impossible, to overcome by predators that have, at best, only equal equipment.

Bee Keeping

Bee Keeping

Make money with honey How to be a Beekeeper. Beekeeping can be a fascinating hobby or you can turn it into a lucrative business. The choice is yours. You need to know some basics to help you get started. The equipment needed to be a beekeeper. Where can you find the equipment you need? The best location for the hives. You can't just put bees in any spot. What needs to be considered when picking the location for your bees?

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