Sequence of Behaviors to Locate and Consume Prey
Prey Habitat Location

For predators associated with ephemeral habitats (e.g. agricultural crops), adults must locate habitats with prey through seasonal movements into and out of cropping systems. Olfactory and visual cues are likely used by adult predators to locate suitable habitats (Hagen 1987). A great deal is known about habitat location for relatively few predatory species, thus our ability to generalize patterns for most predatory species is limited. For example, it is not clear how adult coccinellids, that feed on aphids, locate prey habitats. For one Anatis species, an arboreal coccinellid, plant volatiles from pine needles are used for habitat location.

Volatile kairomones and synomones are known to be used as attractants by selected insect predators. For some predatory species, a blend of compounds, including volatiles from the plants in the habitat as well as prey volatiles, are involved (Hagen 1987). Thus, the distinction between habitat finding and prey finding may not be clearly defined. There is overlap in predatory behaviors and responses which may not fit a set linear sequence of habitat location followed by prey finding.

The role of semiochemicals in prey location is best understood for the lacewing, Chrysoperla carnea (Neuroptera: Chrysopidea). Certain biotypes of C. carnea are not predaceous as adults. Volatiles from aphid honeydew induce C. carnea adults to fly upwind toward a food source. The amino acid tryptophan is presumably the source of the kairomone. The actual volatile chemical is a breakdown product of oxidized tryptophan believed to be indole acetaldehyde. Addtionally, caryophyllene, a relatively common plant volatile, also attracts C. carnea adults and is believed to be a habitat cue (Hagen 1987).

The attraction of C. carnea adults to artificial honeydews varies with the phenology of the crop plant. Applications of oxidized tryptophan on growing alfalfa with few aphids present is very attractant to C. carnea adults, but similar applications to blooming alfalfa are not attractive. The application of caryophyllene, which alone is not attractive, in combination with tryptophan on mature alfalfa, restores attraction. Hagen (1987) concluded that volatiles from the growing alfalfa plants are required in addition to the honeydew-derived kairomone for C. carnea. Thus, a synergistic mixture of plant and aphid derived cues from plants and prey are used by C. carnea to locate prey.

Predators of bark beetles in several Coleopteran families, e.g., Cleridae, Colydiidae, Histeridae, and Trogostidae, are attracted to bark beetle host trees by volatile kairomones composed of terpenes, bark beetle pheromones, or mixtures of tree-based terpenes and pheromones (Hagen 1987).