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From the June 2014 Conservationist

Dobsonfly

Forest Health Corner: What's that bug?

Common insects seen at the Forest Health Lab

By Jessica Cancelliere

Charged with identifying and monitoring insect pests that threaten the health and vitality of New York's forests, DEC's Forest Health Diagnostic Lab in Delmar routinely receives requests from the public to identify insects. Sometimes people are concerned about damage an insect is causing; other times, they are simply inquisitive about what they've discovered. They send photos, descriptions, and occasionally even the actual insect, to the lab.

Here are a few of the fascinating insects that people commonly ask us about.

dobsonfly
dobsonfly

If you enjoy fishing, you may be familiar with the huge, sickle-jawed gray dobsonflies often seen fluttering over water or perched along the sides of rivers and streams. These insects belong to the order Megaloptera, which means "big wings." This order includes the smaller fishflies and alderflies. The eastern dobsonfly (Corydalus cornutus), with a wingspan of almost 6 inches, is the largest Megalopteran in the northeast. Males have massive, extremely sharp mandibles that can be three times as long as their head. Though they appear menacing, the mandibles are used solely to impress females and to position them during mating. However, the smaller, but fierce, jaws of the female can draw blood, and she may inflict a painful bite if handled carelessly.

Dobsonflies spend most of their 2- to 5-year lives as freshwater larvae called hellgrammites. These voracious underwater predators have strong, pinching jaws to help capture and eat aquatic insects, insect larvae, small fish and amphibians. One of the best baits for catching bass and trout, hellgrammites will bite if given the chance. They require clean, unpolluted water, and are often used as indicators of water quality in rivers and streams.

When the time comes, hellgrammites leave the water for good, crawling onto land, and pupating in a damp area, such as under rocks or logs. In June, they emerge as adult dobsonflies. These adults only live for a week or two, during which time they don't eat and only focus on reproducing. Females lay eggs on branches, sticks or plants that hang over the water, and when the eggs hatch, the larvae drop into the water to begin life as a hellgrammite.

giant water bug
giant water bug (or giant electric light bug)

In spring, the lab receives many phone calls from concerned homeowners, inquiring about large, floundering bugs near their porch lights with huge, grasping forelegs and a stout beak. These insects are the giant water bugs, (or giant electric light bug, Lethocerus americanus) belonging to the order Hemiptera, the "true bugs."

Although aquatic throughout their lives, adult giant water bugs have wings and are capable of taking an occasional flight. They don't rely on gills to breathe underwater; rather, they take air at the surface using a pair of short flaps at the tip of their abdomen. They are great swimmers and predators. You may spot them with frogs or fish impaled on their long beak, which they use both as a lethal syringe to inject poisonous saliva, and as a drinking straw though which they suck up a prey item's liquefied body contents.

Giant electric light bugs lay egg masses on wet places near water, like stones or logs. Females of some species, however, will glue their eggs onto the back of a male, who protects and ventilates the eggs until they hatch. It's quite a burden to carry, but ensures that only his sperm fertilizes the eggs on his back.

Long-horned beetles (family Cerambycidae) are a group of often brightly colored beetles of all sizes that sport unusually long antennae. If you pick up a Cerambycid to get a closer look, it will "squeak" by rubbing its head on small ridges inside its thorax. Larvae are borers of dead wood, or of living woody or herbaceous plants. Larger species that live in dead wood have extremely long development times, sometimes decades, and contain symbiotic microorganisms that help them digest their woody meals.

prionid beetle
prionid beetle

Prionid beetles (or tooth-necked longhorns) are the largest of the Cerambycids. They can reach lengths of up to 2.5 inches, and are named for their distinctive spines that run along the sides of their neck. We get many calls from intimidated homeowners after they've spotted one of these big, beefy insects resting on a back porch or marching through a garden. Many people are concerned that these beetles might cause damage to their trees or a garden. Prionid larvae typically develop and feed in rotting wood, especially roots and stumps. Some species, like the broad-necked root borer, are considered pests of fruit and hardwood trees, but typically will only attack weakened ones. The best way to avoid problems with these pests is to keep trees healthy.

white-spotted sawyer
white-spotted sawyer (Photo: University
of Georgia)

A common long-horned beetle in New York is the white-spotted pine sawyer (Monochamus scutellatus). It receives a lot of attention as the most common look-alike of the infamous Asian longhorned beetle, an invasive pest from Asia that threatens our maples and other hardwoods. The white-spotted sawyer is only an inch long, but its strikingly long antennae add another two inches or so. Native pine sawyers are abundant around freshly cut conifer logs, and are often seen by campers at artificial lights at night. The large, club-shaped larvae make a "sawing" sound as they feed inside piles of pine logs.

The Forest Health Diagnostic Lab sees a wide variety of insects, from the common to unusual; from the ordinary to the unexpected. If you need us to identify something, we're here year-round to help; just visit the Insect, Plant and Disease Identification webpage for more information.


Jessica Cancelliere is a diagnostician at the Forest Health Diagnostic Lab in Delmar.

Photo: David Cappaert/Bugwood.org