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General Overview of Predators
The predaceous insects form a large diverse group. Over 16 orders of insects contain predaceous members, in approximately 200 families. Including the spiders and mites, there are probably in excess of 200,000 species of arthropod predators (Clausen 1940, Sweetman 1958, New 1991). Many crops contain a rich assemblage of predators, and it is not uncommon to find (if you look!) 300-500 species of predators in a given crop. Among the non-insect arthropods, spiders (Araneae) represent the largest, most diverse group. Although all known spiders are predaceous, there are 6-8 major families commonly encountered in crops. Although prominent predators, spiders have been little utilized in biological control. The mites (Acari) have a number of predaceous members, most found in the family Phytoseiidae. Mites have been used in a number of biological control projects.
Because of the broad diversity of predaceous arthropods, this course can only provide an overview of the taxonomy and biology of the more "important" groups.
- General Characteristics of Insect Predators:
- (1) kill and consume more than one prey organism to reach maturity
- (2) relatively large size compared to prey
- (3) predaceous as both larvae and adults
- (4) larvae are active with sensory and locomotory organs
- (5) except for predatory wasps that store prey for immature stages, prey are generally consumed immediately
- General Predatory Behaviors:
- (1) Searching - initiated by hunger and stopped by satiation
- (2) Searching Site - inherited behavioral characteristics which are modified by experience
- Frequency of individual prey items in the diet may be influenced by:
- (1) frequency of prey environment
- (2) prey preferences
- (3) competition with other predators
- (4) suitability of prey
- Strategies to locate and capture prey:
- (1) Random searching - The predatory bug, Podisus maculiventris searched bean plants without using cues, but did not search areas repeatedly once a prey was found. Wiedenmann and O'Neil (1991) made behavioral observations for 4 h in the greenhouse with 2 densities of prey (Mexican bean beetle larvae). Random searching based upon a comparison of time budgets for Podisus that successfully found prey vs. those that were not successful.
- (2) Directed searching - characteristic of many predatory Coleoptera -- orientation to objects in the microhabitat -- movement may be guided by features of the environment that increase chances for encountering prey.
- (3) Active searching - use of visual cues and other stimuli to orient to prey at a distance. For example: Dragonflies, Robber flies.
- (4) Ambush - Conserve energy by waiting for prey to approach within a striking distance, raptorial legs -- clasping prey. Examples: Phymatids and preying mantids.
- (5) Trapping - Ant lions. Neuropterans, conical pits in loose sand, larvae wait at the bottom with large sickle shaped jaws.
- (6) Attracting - Lightning bugs -- flashing of one species to attract males of another -- females then consume males.
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