COMMON MISTAKES MADE IN INSECT IDENTIFICATON
Colorado Potato Beetle or Sunflower Beetle?
These two Chrysomelidae family beetles are easily confused because they both have a broad, curved body and are generally light colored with prominent striping.
The feeding habits vary greatly between these two beetles, so the easiest way to distinguish them is to note what plant they were feeding on when you found them.
Sunflower beetles feed only on sunflowers where Colorado potato beetles feed only on certain plants in the nightshade family including potato, eggplant, hairy nightshade, and buffalo burr.
Also, the Colorado potato beetle is larger and darker than the sunflower beetle and the striping on the side of the beetles can be used to identify them. While one of the stripes is broken, resembling an exclamation point on the sunflower beetle, none of the stripes are broken in this manner on the Colorado potato beetle.
Stag Beetle or Larger Ground Beetle?
Stag beetles in the Lucanidae family are relatively uncommon in the region. The larvae develop in dead and decaying wood and the most prominent feature of the beetles is their large mouthparts, which are particularly developed in the male for use in courtship and mating while females use theirs to chew wood.
Very common in the grasslands of our region are various large ground beetles in the Carabidae family in the genus Pasimachus. They have very large, forward-projecting jaws they use to capture and crush their prey.
The dark black color of the ground beetles differs from that of the brown stag beetles and the antennae of the ground beetles are threadlike and straight where the stag beetles have antennae with elbowed, comblike clubs.
Darkling Beetle or Ground Beetle?
Ground beetles are also commonly confused with the darkling beetles in the Tenebrionidae family and the best way to distinguish between the two insect families is to look at where the hindlegs appear to be attached to the body. The legs of the darkling beetle are easily traced to the thorax of the body (or the mid-stage) where the hindlegs of the ground beetles appear to be much further back on the body. (this is due to the fact that the body segment to which the legs are attached is a large plate that covers a part of the abdomen, making it appear that the legs are attached to the abdomen and not the thorax).
The most commonly collected darkling beetles are “stink beetles” in the genus Eleodes which produce smelly defensive chemicals when threatened. However, many ground beetles also produce unpleasant odors.
Another useful characteristic to differentiate between the two families is the antennae. Most darkling beetles have clublike antennae that are slightly enlarged at the terminal end unlike the threadlike antennae of the ground beetles.
Also, ground beetles have large, forward-projecting jaws used to capture and crush their insect prey and darkling beetles have smaller often downward-oriented mouthparts used to feed on plant material.
Rove Beetle or Earwig?
Rove beetles, an unusual family in the Order Coleoptera, have very elongate bodies and lack the long hard wing covers distinctive of most other beetles. Rove beetles are dark-colored and have short wing covers that only cover the thorax enclosing a pair of folded membranous wings.
Often rove beetles are mistaken for earwigs in the Order Dermaptera because the general elongate body shape and short wing covers are similar, however; earwigs can be distinguished by the presence of forceps on the hind end lacking on rove beetles. On male earwigs the forceps are bowed, and on female earwigs the forceps are straight.
Another important difference between rove beetles and earwigs s their diets. While rove beetles are predators of other insects, particularly fly larvae, while earwigs feed on many different things including other insects but also on soft plant parts including flowers and tender seedling.
As a nuisance insect, earwigs (especially the European earwig) are very common and familiar insects in our region so many times people assume they’ve found an earwig in the home when a rove beetle crosses their path.
Damselfly or Antlion?
While the immature stages of the damselfly develop in water, the larvae of antlions are predators that dig pits in sandy soils to trap prey, usually ants.
As members of the Order Neuroptera, the wings of the antlions fold flat or rooflike over their abdomen while at rest. As members of the Order Odonata, damselflies cannot fold their wings so they stay extended, pointing upward while at rest. Antlion wings also possess more veins and rarely fly during the day where damselflies are primarily day fliers.
The antennae are another distinctive characteristic as antlions have conspicuous clubbed antennae and the damselflies have short, bristlelike antennae.
Green Lacewing or Mayfly?
Adult stages of both Order Ephemeroptera mayflies and Neuroptera Order green lacewings are delicate insects with clear wings. While they may resemble each other superficially, one way to distinguish these two groups of insects is the manner in which they hold their wings when at rest. The green lacewings fold their wings over their bodies while the wings of many mayflies remain erect and do not fold.
Also, green lacewings possess long, beaded antennae where the antennae of mayflies are reduced to small bristles. A more obvious characteristic present on mayflies is the presence of two or three long, filamentlike “tails” on the hind end absent on green lacewings.
Location can be another characteristic used to narrow the two as green lacewings are one of the most beneficial garden insect predators, common inhabitants of gardens and fields. Mayflies are insects that develop in water emerging only for a brief period as adults.
Peach Tree Borer or Ctenuchid Moth?
Both clearwing borers and ctenuchid moths fly during the day and mimic wasps. Both in the Order Lepidoptera, the plant-damaging Sesiidae family peach tree “clearwing” borers is less often collected than the also dark-winged Arctiidae family ctenuchid moths.
Although the front wings of both moths are dark, the hind wings of the female peach tree borer are largely clear, lacking colorful scales. Ctenuchid moths have dark hind wings and lack a bright orange band across the abdomen present in female peach tree borers.
Harlequin Bug or Twospotted Stink Bug?
Both brightly colored stink bugs in the Pentatomidae family, the easiest way to distinguish these two species is by their habits. While the harlequin bug is a well-known pest species attacking plants in the cabbage family, the twospotted stink bug is a predator of other insects and an important natural enemy of the Colorado potato beetle. The twospotted stink bugs are more generally distributed throughout the region than harlequin bugs.
Harlequin bugs are generally red-orange with numerous black and white markings where the twospotted stink bug may be black, gray, or red in color. However, the twospotted stink bug has a distinctive U-shaped pattern on its back between its wings. The name twospotted comes from the two dark patches behind its head on the prothorax.
Lygus (Plant) Bug or Aphid?
While plant bugs in the Order Hemiptera, Family Miridae can often be confused with aphids in the Order Hemiptera, Family Aphididae in their immature stages, there are many behavioral differences that help for identification in the field as well as other differentiating characteristics that can be revealed upon close inspection of the species.
Plant bugs are usually active insects, particularly if disturbed, and can run rapidly over the plant where aphids are always quite slow-moving. One of the most common kinds of plant bugs is the Lygus bug, which is a pest of several crops grown in the region. Also, plant bugs are usually solitary insects usually associated with developing seed heads while aphids often occur in colonies.
Some characteristics observed under magnification are very useful in identification. Most aphids have a pair of pipeline cornicles protruding from the hind end and the mouthparts of aphids appear as a small cone underneath the insect between the front legs. The piercing-sucking mouthparts of plant bugs are much more visible since they project from the front of the head and there are no cornicles protruding from the hind end of plant bugs.
Box Elder Bug or Small Milkweed Beetle?
Two commonly collected insects that are often confused are the box elder bug (Boisea trivittatum) and the small milkweed bug (Lygaeus kalmia). Both are similarly shaped, about ½ inch (1.3 cm) long and marked with red and black.
The box elder bug is a commonly known house pest, sometimes moving indoors in large numbers for winter shelter during the fall. The box elder bug develops primarily by feeding on the seeds of the box elder maple while the small milkweed beetle feeds on a wide variety of plants primarily as a seed feeder.
The easiest way to differentiate between them is the small milkweed beetle has two white spots near the end of the front wings while box elder bugs lack these white markings.
Bees or Bee-Mimicking Flies?
Bees, such as honeybees and bumblebees in the Order Hymenoptera are capable of stinging when handled or attacked. For this reason, many other insects (most notably flies in the Order Diptera) have developed as mimics of bees to appear to have this defensive ability. The bee-mimicking flies are often colored and patterned and some even have the ability to buzz and may also visit flowers for nectar, however; none of them can sting.
Close inspection can distinguish the two groups easily. All bees and wasps have two pair of wings while flies only possess one pair. Although this is a clear distinction between the orders, the wings of wasps and bees are often hooked together and may appear as a single pair.
Bees and wasps also possess a distinct constriction between the thorax and abdomen (often called the “wasp-waist”) and this attachment is usually broad among flies although some even mimic this feature.
Perhaps the best distinguishing feature is the antennae. The antennae of flies are often short, only a tiny bristle. Bees and wasps possess long, conspicuous antennae that are elbowed with many segments.
Conifer Seed Bug or Assassin Bug?
Conifer seed bugs in the Family Coreidae Genus Leptoglossus are large brown insects that feed on the seeds and leaves of plants. Occasionally they enter homes during the winter months and become a nuisance. Assassin bugs in the Reduviidae family are predators of other insects, and although one species called the masked hunter can sometimes occur indoors, most are found on outdoor plants.
Both conifer seed bugs and assassin bugs can be similar in size and possess a distinct “beak” containing the mouthparts. However the head of assassin bugs is more elongate and the mouthparts are more visible.
The legs are the best distinguishing feature as portions of the hind legs of conifer seed bugs are broad, sometimes leading to the name “leaffooted bugs”. Assassin bugs have narrow hind legs and thickened front legs, used to grasp and hold prey.
Milkweed Beetle or Spotted Asparagus Beetle?
Two common orange-red beetles with distinct dark spots are the milkweed beetles in the genus Tetraopes and the spotted asparagus beetle, Crioceris duodecimpunctata (Linnaeus). While Milkweed beetles develop as borers in the stems of milkweed plants, the spotted asparagus beetle develops in the fruit of the asparagus.
Although their general shape and coloration is similar, their size differences are dramatically different. Milkweed beetles are up to one inch (2.5 cm) long while the spotted asparagus beetle is less than ½ inch (1.3 cm) long. The spotted asparagus beetle is also more highly spotted with eleven spots and is a darker red than the milkweed beetles.
Milkweed beetles also produce an audible squeak when picked up and held to ear while the spotted asparagus beetle will not.
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