Beneficial Insects - Predators

Beneficial insects (natural enemies) are predators and parasitoids; they maintain the checks and balances of the insect world, helping to prevent pest populations from getting out of control and causing damage to crops and garden plants. Many of these beneficial insects rely on floral rewards (pollen and nectar) for food so they can be fostered and attracted with a healthy, diverse native planting.

Ladybird Beetle Larva
Feeding on an Aphid
These predators and parasitoids hunt and feed on prey in either or both the adult and larval forms. Soldier beetles, lady bird beetles, syrphid flies, solitary wasps, crab spiders and minute pirate bugs are some important beneficial insects.

The abundance and diversity of beneficial insects in a particular landscape depends on: 
  • the diversity of the landscape
  • the quality and abundance of forage plants 
  • the availability of prey
  • the number and quality of nesting sites
  • the overall health of the plant community 
Native plants play a key role in attracting beneficial insects (and more pollinators). Beneficial insects feed on floral resources and seek shelter in the foliage when not hunting or parasitizing prey. A stressed plant, including one poorly situated, is more susceptible to pests. When selecting plants, make sure to match the site with the habitat where the native plant occurs naturally.

Predators feed on insects as adults and/or as larvae. Solitary wasps are excellent predators of large prey; prey, once caught, are cached in the nest live for the hatched larvae to feed on and fuel development. They help control caterpillars, sawfly larvae, katydids, crickets, and grasshoppers - all insects that feed on foliage.

Predator Profile - Great Golden Digger Wasp, Sphex ichneumoneus
Nest Excavation - The female excavates clumps of soil and
holding the clumps between her mandibles
and forelegs, backs out of the nest and deposits
the soil away from the nest entrance. 
Great golden digger wasps are solitary wasps that nest in the ground. These large, brightly colored wasps are prey on crickets and katydids.

Nests are excavated in sand or gravelly soil. Females can be observed excavating nests in mid-summer, pictured on the left excavating a nest in mid-July this year.

Females paralyze prey and fly it back to the nest grasping the prey with their legs and holding it underneath them (left). The wasp places the prey on the ground near the nest entrance. She then checks the nest before placing the prey inside. Females often drag the prey backwards into the nest hole grasping it with her mandibles. Once the prey is cached, a single egg is laid on each cricket/katydid. When the larva hatches, it begins feeding on the prey until pupation.

These wasps are common in late summer and visit a variety of native plants that offer nectar like culver’s root, (Veronicastrum virginicum), rattlesnake master (Eryngium yuccifolium),  purple prairie clover (Dalea purpurea) and spotted beebalm (Monarda punctata) (left).

Providing native plants for nectar foraging helps support these solitary wasps and fuel their hunting activities. A diverse native plant community also provides cover for their prey.

Predator Profile - Syrphid Flies, Family Syrphidae
Syrphid flies are active from spring through late fall and visit a large variety of native plants where they can access floral resources, typically in less complex flower forms.

Adult syrphid flies visit flowers to feed on both pollen and nectar. Females foraging for pollen often hold the flower's anthers with their forelegs while they sponge up the protein-rich pollen with their mouthparts.

Many syrphid flies are excellent mimics and are often mistaken for bees or wasps as their coloration and behavior mimics bees and wasps (left). This mimicry helps protect them from predation by birds and other predators.

Larvae look like small caterpillars and feed on aphids or other small, soft-bodied insects (left). Look for the larvae on the underside of leaves where there is a large aphid population. They often feed on aphids that are much larger than themselves.

Pesticides have a serious impact on beneficial insect (and pollinator) populations. If insecticides are applied to control a problem pest, the beneficial insect population is eliminated at the same time. It often takes less time for the pest population to recover from an application than it does for the beneficial insect populations to recover. Continous pesticide use can result in the ongoing imbalance of pest and beneficial insect populations.