Beneficial Insects Commonly Encountered by Gardeners
Insects are invertebrate animals that are distinguishable by having three pairs of legs in the adult stage and their body divided into three segments – head, thorax and abdomen. They are the most diverse group of organisms, meaning that the quantity of species of insects is higher than any other group, animals or plants. In the United States, there are approximately 91,000 described species of insects. They can provide vital ecological services, such as pollination, pest control, decomposition and maintenance of wildlife species. This article describes beneficial insects, including pollinators, predators and parasitoids, commonly encountered in gardens of West Virginia that are directly related to vegetables and ornamentals.
Bees are insects that belong to the order Hymenoptera. Bees are pollinator agents that transfer pollen grains from the male to the female floral organs. They are commonly found in gardens, specifically on flowering plants because they feed on pollen and nectar.
Biology and behavior of bees are different between species. Each bee species is attracted to different plant species and active during different times of the year. Honeybees, a non-native species, are most commonly used for commercial pollination of agricultural crops. However, many other native bee species provide valuable pollination services.
It has been estimated that North America has about 4,500 bee species, while West Virginia has 124 native bee species. There are approximately 430 and 400 bee species in neighboring states Pennsylvania and Virginia, respectively.
Wasps also belong to the order Hymenoptera. Most wasps have a thin or pinched waist and are black or have various markings of white, orange or yellow. European hornets and cicada killers are the most popular wasps requested for insect identification at WVU Extension. These wasps are considered beneficial insects because they feed on garden pests as well as other pests, such as houseflies. However, they tend to be unwanted in gardens because of their potential to sting people.
In general, solitary wasps, such as cicada killers, want nothing to do with humans and will rarely sting, even when bothered. Cicada killers only sting in self-defense. In contrast, social wasps, like European hornets which live in colonies, can sting when they perceive their nest or territory is threatened. The best and easiest way to tell wasps apart is to look at the relative size of the wasp and the pattern on the abdomen.
There are many other species of wasps that infect insect pests in the garden as parasites – they are called parasitoid wasps. Depending on the species, parasitoid wasp females lay eggs on or in the bodies of their prey. Once eggs hatch into larvae, larvae feed and reproduce inside their hosts. Depending on the species, parasitoids kill their host during the egg, larval or adult stage. Parasitoids might go unnoticed because of their small size and inability to sting humans.
Lady beetles, also known as ladybugs, belong to the order Coleoptera. They are one of the most common predators in gardens. They feed on different pests, including aphids, spider-mites, whiteflies and others.
Many species of lady beetles are native, but the multicolored Asian lady beetle was intentionally introduced in California in the early 1900s as a biocontrol agent. The multicolored Asian lady beetle can be distinguished from other species of lady beetles by a pair of white markings behind the head that forms the shape of an “M.”
Lady beetle larvae are “alligator-shaped” and covered with small flexible spines. The color of larvae varies within species. They are predators at larval and adult stages.
Lacewings are common predatory insects in gardens and belong to the order Neuroptera. Lacewing larvae, also known as aphid lions, are voracious predators that feed on several pests, such as aphids, spider-mites, whiteflies and others. Larvae have hooked jaws protruding from their heads, while lacewing adults usually feeds on pollen, nectar and honeydew. Adults are light green with long slender antennae, golden eyes and long, delicately veined wings that are transparent and extend beyond the abdomen. Adults are poor fliers and are attracted to lights at night.
Praying mantids, also known as mantises, belong to the order Mantodea. Praying mantids are popular insects for several reasons. They have a "neck" that allows the head to rotate 180 degrees while waiting for a meal to wander by. Also, females kill their sex partners in up to 46 percent of their encounters, but that does vary within species. Praying mantids are very efficient and deadly predators that capture and eat a wide variety of insects and other small prey. However, their overall value as a biocontrol agent is relatively small compared to lady beetles and green lacewings. This is due to their cannibalistic nature, which limits the number of mantids in an area. Placing large numbers of egg cases may not increase the population due to the fact that mantids tend to move away from others to find suitable coverage and food sources.
Minute Pirate Bugs
Minute pirate bugs, also known as flower bugs and Orius, are common predators in gardens. They belong to the order Hemiptera and feed on aphids, armyworms, thrips, spider-mites, whiteflies and others. Adults are distinctive by their black and white oval-shaped appearance. Nymphs resemble adults but are smaller and wingless. They are yellow-orange to brown in color, teardrop-shaped and fast moving. Both adults and nymphs feed by sucking juices from their prey through a sharp, needle-like beak called the rostrum. During the fall, they occasionally bite humans and can move into homes.
Wheel bugs are moderately common in gardens. Like minute pirate bugs, wheel bugs belong to the order Hemiptera and suck the juices from their prey. They have a distinctive semicircular crest that resembles a cogwheel or chicken's comb. The wheel bug is one of the few predators that attack the brown marmorated stink bug, which is a serious introduced pest of many crop plants, like tomatoes and apples. Wheel bugs also attack a wide variety of insects including aphids, moths, butterflies, sawflies and beetles (including lady beetles). Both nymph and adults are predators. Wheel bugs should be avoided or handled with caution because they can bite humans. Their bite has been described as worse than a sting from a bee, wasp or hornet.
Several beneficial insects that are common in gardens are also commercially available. For example, lady beetles, lacewings, praying mantises, minute pirate bugs, parasitoid wasps and others can be purchased from several insectaries and released in gardens. To prevent beneficial insects flying away from gardens, different plant species with varying blooming times should be planted to provide alternative food sources, such as pollen and nectar. Also, pesticide application should be avoided.
Author: Carlos Quesada, WVU Extension Entomology Specialist
Last Reviewed: July 2021