HPIPM:Biological Predators

Author: Whitney S. Cranshaw

Insect Predators

Several insects develop as predators of insects or other arthropods. The immature stages are free living hunters, that move about and consume many prey in the course of development. Adults may have similar habits or may feed instead on nectar, pollen, honeydew and similar materials.

Lady Beetles (Lady Bugs, Ladybird Beetles)

Coleoptera: Coccinellidae

Lady beetles are often the most familiar and widely recognized of the insect predators. They are common insects and about 80 species occur in the High Plains/Rocky Mountain region. However, only a few of these are common to agricultural fields.

Adult lady beetles have a characteristic a round-oval shape, most are brightly colored and often have bold patterning on the wing covers. Adult and, particularly, larval lady beetles feed may feed on large numbers of small soft-bodied insects. Some are generalists that will feed on many kinds of insects - aphids, small caterpillars or beetles, insect eggs. Others have more specialized habits. For example, the tiny "spider mite destroyers" (Stethorus species) feed on mites. Adults of most species also feed on pollen, nectar and honeydew and the presence of such foods may be important in conserving and enhancing the activity of these beneficial insects.

Most lady beetles lay eggs in masses of 5 to 30 orange-yellow eggs. The eggs are quite distinctive, although they somewhat resemble those produced by some leaf beetles (Chrysomelidae family). Eggs are usually laid near colonies of in­sects that provide food for their larvae.

The immature or larval stages look very different from the more familiar adults and often are over­looked or misidentified. Lady beetle larvae are elongated, usually dark colored and flecked with orange or yellow. Some species may have fleshy spines and a few are covered with white wax. Larvae are active hunters that can crawl rapidly over plants, search­ing for food. Most can complete their larval stages in two or three weeks after which they pupate attached to the plant or nearby objects.

Most lady beetles survive winter as an adult in sheltered locations. In some areas of the country the convergent lady beetle (Hippodamia convergens) migrates to higher elevations during its dormant periods and often aggregates in large numbers. These mass aggregations serve as the source of adult lady beetles sold through some nurseries. A fairly new species in North America is the multicolored Asian lady beetle (Harmonia axyridis), which has a nuisance habit of moving into homes following autumn frosts. Another lady beetle now common in agricultural fields is the sevenspotted lady beetle (Coccinella septempunctata), which was purposely introduced into the region during the late 1970's and early 1980's.

Ground Beetles

Coleoptera: Carabidae

Ground beetles are common insects of field varying in size from about ½ inch to 1 ¾ inches. Most are elongate-oval in form, with prominent forward-projecting jaws. They have hard wing covers that are typically dark, but may have metallic coloration. Adults can be very active and fast moving although usually spend days under cover of leaf litter and other sheltering debris. Larvae are also predators and are usually active at the soil surface or tunnel in the upper soil.

Almost all ground beetles develop as predators and may feed on a wide variety of insects. As their name may indicate most restrict their activity to areas at or around the soil surface and are poor climbers.

A group of insects now commonly classified with the ground beetles are the tiger beetles (primarily Cicindela spp.). These are very active insects and most readily fly. Both adults and larvae are general predators of other insects, although larvae primarily hunt by ambush from soil tubes where they develop. Tiger beetles have little effect on agricultural insects but may be commonly observed as they make short flights on roadways.

Rove Beetles

Coleoptera: Staphylinidae

Rove beetles are odd-looking beetles, elongate in form with very short wing covers. Both the adult stage and larvae are general predators of insects found in soil. Some of the more important rove beetles feed on fly larvae, including root maggots and those that develop in animal manures.

Collops Beetles

Coleoptera: Melyridae

Collops beetles (Collops species) are moderately sized (1/5 to 1/3-inch), usually bluish-black with red or orange markings. They may be found feed on pollen at flowers but also eat insect larvae, aphids and other small, soft-bodied insects. Collops bipunctatus is the species most common in agricultural crops.

Soldier Beetles

Coleoptera: Cantharidae

Soldier beetles are elongate beetles with have fairly soft wing covers, lending them the name ‘leather-winged beetles’. Adults are usually patterned with yellow or orange and black markings. Some Cantharis species found in the northern High plains and western states are predaceous in the adult stage, feeding on aphids, insect eggs, and other soft-bodied insects. The rarely observed larval stages develop in the soil and are also predaceous. The most commonly observed soldier beetles, such as the Pennsylvania leatherwing (Chauliognathus pennsylvanicus) are not predaceous in the adult stage and feed primarily on pollen. They are commonly seen at yellow flowers late in the season, often coupled in mating.

Green Lacewings

Neuroptera: Chrysopidae

Green lacewings (Chrysoperla spp.) are common insects of fields. Adults are pale green or light brown insects with clear, highly-veined wings they hold over the body when at rest. Adults of the common species feed on nectar, pollen and honeydew - although adults in the genus Chrysopa also feed on small insects. The females lay a distinctive stalked egg, approximately one half inch in height. Eggs may be laid in small groups or singly on leaves or stems of plants.

Lacewing larvae, sometimes called "aphid lions", are predators of a wide range of insects, including thrips, small caterpillars and beetles as well as aphids. In general shape and size, lacewing larvae are superficially similar to lady beetle larvae. How­ever, immature lacewings usually are light brown and have a large pair of viciously hooked jaws projecting from the front of the head. Pupation occurs in a nearly spherical, pale-colored cocoon attached loosely to foliage.

Brown Lacewings

Neuroptera: Hemerobiidae

Brown lacewings have the same general form as the closely related green lacewings, but have ligh brown wings and are usually smaller. Larvae are general predators and have very prominent jaws that project even more forward than those of green lacewing larvae. Adults are also predators of aphids and other small, soft-bodied insects. Brown lacewings are uncommon in agricultural fields and occur primarily in wooded or brushy areas.

Syrphid Flies (Flower Flies, Hover Flies)

Diptera: Syrphidae

Syrphid flies are common brightly colored flies. Typical mark­ings are yellow or orange with black, and they may look very similar to bees or yellowjacket wasps. However, syrphid flies are harmless to humans. Usually adult syrphid flies can be seen feeding at flowers.

It is the larval stage of the syrphid fly that is an insect predator. Variously colored, the tapered maggots crawl over foliage and can daily down dozens of aphids. Syrphid flies are particularly important in controlling aphid infestations early in the season and are capable of entering the tightly curled leaves which some aphids produce. A tarry excrement produced by syrphid fly larvae is diagnostic of their activities.

Aphid Flies/Predatory Midges

Diptera: Chamaemyiidae, Cecidomyiidae

Some small flies develop as predators of aphids. Larvae of the aphid predator midge, Aphidoletes aphidimyiiza, are bright orange. They are common in colonies of many aphids found associated with vegetable crops and are also sold for aphid control in greenhouses. Leucopis spp. are reported to develop in colonies of Russian wheat aphid. Adults of these are small, grayish inconspicuous gnat-like flies.

Robber Flies

Diptera: Asilidae

The robber flies are the dominant insect predator of the air around prairie sites. The adults are large, elongate flies that dart from vegetation to snare almost any suitably sized insect that flies or hops past. They have well developed front legs for grasping and a dagger-like mouthpart that rapidly incapacitates the prey. Biology of the larval stage is poorly understood but most are thought to be predators of soil insects.

Dance Flies

Diptera: Empididae

Dance flies are typically small and many are midge-like in appearance. However, most are predaceous in both adult and larval stages. The adults have sucking piercing-sucking mouthparts that they use to feed on aphids, psyllids, and small flies. Adults can be fairly common in the vegetation of potatoes and other dense crops. Habits of the larvae are poorly studied but some feed on insects around cattle manure.

Mating behaviors of the dance flies are unusual in that males will capture prey and present it to females. Mating swarms also occur with the dance flies.

Predatory Thrips

Thysanoptera: Aeolothripidae, Thripidae

Although even pest thrips (e.g., flower thrips) are known to occasionally feed on small arthropods such as mites the bandedwinged thrips are primarily predators. These are fairly large thrips with black and white banding. They are most often found feeding among colonies of other thrips or spider mites. The sixspotted thrips (Scolothrips sexmaculatus) is a predatory species found in some of the region.

Predatory Stink Bugs

Hemiptera: Pentatomidae

Although some stink bugs feed on plants, such as the harlequin bug, others are predators of other insects. Those that feed on insects are capable of subduing large prey, such as caterpillars or beetle larvae, which they impale with piercing sucking mouthparts. Among the predatory stink bugs more commonly found in gardens are the twospotted stink bug (Perillus bioculatus), which specializes in beetle larvae such as the Colorado potato beetle, and the spined soldier bug (Podisus maculiventris), which primarily feeds on caterpillars.

Assassin Bugs

Hemiptera: Reduviidae

Assassin bugs are moderately large insects that can also feed on fairly large prey, such as insect larvae. Most assassin bugs are elongate in form, have a pronounced 'snout' on the front that is the base for the stylet mouthparts, and are spiny. De­spite their prodigious ability to dispatch most garden pests, they rarely become very abundant since they in turn succumb to many natural enemies of their own.

Common assassin bugs associated with crops include the spined assassin bug (Sinea diadema), the 'bee hunter' group (Apiomerus spp.), and several elongate assassin bugs found in the genus Zelus. Of even more dramatically slender form are the thread-legged bugs (Emesaya species).

One group of assassin bugs common to gardeners are the ambush bugs (Phymata spp.). These are heavier bodied than other assassin bugs and have enlarged forelegs. Ambush bugs typically occur around yellow or orange-colored flowers and capture insects that visit. Adults are present in late summer.

Damsel Bugs

Hemiptera: Nabidae

The damsel bugs are considerably smaller than assassin bugs (ca. 1/4-inch) and usually dark yellow or pale brown. Similar to the assassin bugs the forelegs are slightly thickened to assist in holding prey. Damsel bugs develop as general predators of insect larvae, small soft-bodied insects and insect eggs. Common species include Nabis alternatus and N. americoferus.

Big-eyed Bugs

Hemiptera: Lygaeidae

Most seed bugs (Lygaeidae) feed on seeds and foliage, with a few such as the chinch bugs and false chinch bugs occurring as significant plant pests. However, one genus (Geocoris), known as the big-eyed bugs, develop as predators of caterpillars, spider mites, aphids and many other insects. The very large eyes that may extend over the prothorax are distinctive of this beneficial group of seed bugs.

Minute Pirate Bugs

Hemiptera: Anthocoridae

The smallest of the predatory "true" bugs commonly found in yards and gardens (typically about 1/16-inch), minute pirate bugs feed on smaller arthropods, such as spider mites, thrips, aphids, and insect eggs. The adults are distinctive with black and white markings; immature forms are generally a uniform straw color and may about the size of their aphid prey. Common genera include Orius, Triphleps, and Anthocoris.

Phytoseiid Mites

Acari: Phytoseiidae

Many types of mites are predators of insects and mites on both plant and in soils. The phytoseiid mites are most common on plants with Amblyseius fallacis being the most common species on field crops of the region. Phytoseiid mites are pear-shaped and considerably more active than plant feeding species they use as prey. Most are generalist predators and may feed on spider mites, eriophyid mites, thrips, and eggs of insects; pollen may supplement their diet. Predatory mites can be important in managing spider mites in some sites, but often are limited by needs for higher humidy than do spider mites. They are often very susceptible to insecti­cides.