Garden Allies: True Bugs

By: Frederique Lavoipierre
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Frederique Lavoipierre is Education Program manager at Santa Barbara Botanic Garden. She also teaches classes and workshops on many aspects…

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A jagged ambush bug (Phymata sp.) Illus: Craig Latker

Will the True Bug Stand Up

“Bug” is such a useful word. Annoying people “bug” us, spies plant “bugs,” computers get “bugs,” and, if we catch a “bug,” we’re sick. When it comes to the world of small insects, we often use “bug” as a catch-all, but the word has a more specific meaning in entomology, referring to just one order of insects, Hemiptera, distinguished from all other insects by the collective name “true bugs.”

When a bug’s common name is written as two words, such as assassin bug, stink bug, or ambush bug, it belongs to the suborder Heteroptera. If “bug” appears as the end of a single word, the creature belongs to a different group; for instance, ladybugs are beetles (Coleoptera), doodlebugs are antlion larvae (Neuroptera), and pillbugs are crustaceans, not insects. Other suborders were a later inclusion in Hemiptera, which may explain why their common names are written as one word. Similar rules apply in other insect orders, such as the flies: syrphid flies and house flies are true flies (Diptera), while a dragonfly is in the order Odonata, and a butterfly is a member of the Lepidoptera. Rules of scientific nomenclature can also give insight into the type of organism being discussed. For instance, knowing that, in Greek, ptera means “wing,” and hemi means “half” sheds light on the meaning of Hemiptera and two of its suborders: the former Homoptera (same-winged) includes aphids, cicadas, hoppers, spittlebugs, scales, mealybugs, and whiteflies; Heteroptera (different-winged, the subject of this article), includes shield bugs, minute pirate bugs, and box elder bugs.

A Distinction of Wings

Look closely at a member of the Heteroptera, and you will see how the order comes by its scientific name. The tips of the first pair of wings are membranous; heteropterans can often be recognized simply by examining their wings. However, juvenile bugs may not have wings yet, the Homoptera, when winged, have uniformly membranous wings, and some bugs never grow wings at all. For practical purposes, true bugs can always be identified by their unique piercing, sucking mouthparts, shared by all members of the order. Those mouthparts are used for piercing plants, animals, or, in some cases, also for defense. Bugs are notable for their remarkable array of defenses, especially chemical weaponry. All Heteroptera are distinguished by having scent glands, immediately evident to anyone biting into a raspberry that has been visited by the common stink bug, but scent glands are not always so easily detected.

Many bugs are cryptic—masters at the art of hiding by camouflage (blending into a background), or masquerading as an inanimate object (a leaf, for instance) of no interest to predators or prey. Bugs also commonly engage in mimicry, imitating other organisms such as bees, wasps, or ants. Some bugs are adorned with spines or other forms of physical defense.

True bugs are hemimetabolous, undergoing an incomplete metamorphosis; the juveniles resemble the adults, but without fully developed wings. Immature hemimetabolous insects, such as bugs and grasshoppers, can often be recognized by the short “wing buds” developing outside the body. Holometabolous (undergoing a complete metamorphosis) insects, such as butterflies and beetles, exhibit much greater differences between the larval and adult stage, and wings develop only during the pupal stage. For gardeners, the important difference between these two types of metamorphosis is that hemimetabolous juveniles and adults feed on the same food source, while holometabolous juveniles and adults often use completely different food sources.

A minute pirate bug (Anthocoris sp.) Illus: Craig Latker

Feeding Patterns

Heteroptera can be grouped by habitat—either terrestrial or aquatic. Terrestrial groups are further subdivided into plant-eating species, predaceous species, and obligate blood-feeders (not treated here). Exclusively predatory are several terrestrial families, including damsel bugs (Nabidae) and assassin bugs (Reduviidae). Others, such as spined soldier bugs (Pentatomidae), belong to families with principally herbivorous species. Some bugs are active hunters, but many, such as ambush and assassin bugs, are sit-and-wait predators, pouncing on inattentive prey that wanders by.

Many heteropterans are herbivores, but relatively few species are significant garden pests. Piercing mouthparts make pest heteropterans difficult to control with sprays, and pest management is further complicated because, at certain times, distinguishing between pest and predator bugs can be difficult; soldier bugs can closely resemble stink bugs, for instance. Some leaf bugs (Miridae) and some minute pirate bugs (Anthocoridae) can behave as both pest and predator, further complicating pest management.

True bugs are part of the interdependent garden food web; in addition to feeding on pest species, many provide a good source of food for other insects, birds, lizards, and spiders. The best pest management strategy is a well-planned habitat garden, where all may live in relative harmony. Offer places for bugs to hide and hunt, then keep an eye out for damsel and big-eyed bugs, and the aptly named assassin, soldier, and minute pirate bugs to show up. If you are lucky, you will one day see an ambush bug, resembling a miniature dinosaur, perched on the goldenrod flowers they favor.

 

An assassin bug (Zelus sp.) Illus: Craig Latker

In a Nutshell

Popular Names:

Plant bugs, minute pirate bugs, damsel bugs, assassin bugs, ambush bugs, seed bugs, stink bugs, spined soldier bugs. All are considered true bugs.

Scientific Name:

Order: Hemiptera. Suborder: Heteroptera. (Other suborders will be covered in a future article.)

Common Families:

Plant bugs (Miridae), by far the largest family, includes both pest and beneficial species. Flower or minute pirate bugs (Anthocoridae) are mostly predators, with a few herbivores. Damsel bugs (Nabidae), assassin bugs and ambush bugs (Reduviidae) are exclusively carnivorous. Seed bugs (superfamily Lygaeioidea) include the big-eyed bug, a predator, but also many pest species. Shiny blue-black nymphs of largid bugs (Largidae), with their prominent red spot, are often mistaken for beetles. The stink bug family (Pentatomidae) includes some predators (spined soldier bug); closely related shield bugs (Scutelleridae) are all herbivores. Knob-kneed stilt bugs (Berytidae) are mainly herbivores. Leaf-footed bugs (Coreidae) are all herbivores; many are pests, as are scentless plant bugs (Rhopalidae), which include box elder bug.

Distribution:

Most families include common, widely distributed garden species.

Life Cycle:

May lay eggs on plant tissue or insert eggs into plant tissue, under bark, and in crevices. Eggs may be laid singly or in groups. Heteroptera have five nymphal instars (stages between molts); winged species develop wings only in the last, adult instar.

Appearance:

Varied; from minute to 6/10 inch; many have a prominent triangular ‘scutellum’ (hard plate or scale) visible on the dorsal (back) side. True bugs are readily distinguished by their piercing, sucking mouthparts.

Life Span:

Some have multiple generations annually (multivoltine); others have only a single generation (univoltine), especially in cold climates.

Diet:

Carnivorous species feed on insect eggs, aphids, caterpillars, leaf hoppers, thrips, mealybugs, scale insects, whiteflies, beetles and other pests. Some are generalists; many are host-specific. Some minute pirate bugs prey on the larvae of leaf-mining flies and moths.

Favorite plants:

Goldenrod, yarrow, and other composite plants provide good places for assassin and ambush bugs. Damsel bugs frequent grasses. Minute pirate bugs are attracted to many kinds of flowers.

Benefits:

True bugs eat a wide variety of garden pests.

Problems:

Some true bugs may become pests. Pest bugs can often be successfully excluded from garden crops with row covers.

Interesting facts:

In some cultures, Hemiptera provide a valuable source of protein. In Mexico, the eggs of aquatic bugs, such as water boatmen and backswimmers, are collected to make flour. Although insects originally evolved from marine arthropods, a single genus of water striders is the only pelagic insect today.

Sources:

Beneficial bugs quickly find suitable habitat in gardens. A few species are commercially available.

More information:

Bugs of the World, McGavin and Preston-Mafham,1999.

http://www.nhm.ac.uk/nature-online/life/insects-spiders/common-bugs/hemiptera/. A fun website with great information about bugs and more (from the Natural History Museum in London).

It’s All Greek to Me. A short essay on classification: and nomenclature.