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Bug of the Week

Week of August 13th, 2018: Corn Earworm

Photo of a Corn Earworm larva feeding inside the tip of an ear of corn.

Corn Earworm Larva (some of these same critters were just found yesterday, August 13th in Dixmont, Maine). Staff Photo.

The Corn Earworm (Helicoverpa zea) is a major pest in agriculture, affecting not only corn, but many different crops. It is serious enough in cotton and tomato to warrant a separate name in those crops: Cotton Bollworm and Tomato Fruitworm. The insect is also abundant in the wild, which is a major reason for its overall success. The larvae vary tremendously in color, ranging from yellow to green to brown or even purple.

Corn earworm is distributed worldwide but it cannot overwinter in the northeastern United States. The moths migrate to Maine from southern states around mid-July. The night-flying female moths search for fresh (green) corn silk on which to lay their eggs. The eggs are laid singly on the silk, although several may be laid on one silk mass. Each female can lay several hundred eggs. If fresh silk is not available, they may lay eggs on other hosts such as tomatoes or peppers. The eggs hatch in two to 10 days. The newly-hatched larvae feed on the corn silk, working their way down the silk channel to the tip of the ear. Once there, the larvae feed on the silk and developing kernels. The feeding area becomes filled with moist waste. This damage causes severe economic loss, and may go unnoticed until harvest.

pair of corn earworm larvae on an ear of corn corn earworm larva feeding on an ear of corn a corn earworm moth on a corn leaf a Corn Earworm moth

Detailed Fact Sheet: Managing Insect Pests of Sweet Corn (includes Corn Earworm)

Week of August 6th, 2018: A unique and rather rare fly called a “Small-headed Fly”

Photo of a small fly called a Small-headed fly, resting on a maple leaf.

A Small-headed Fly on the underside of a maple leaf in Etna, Maine, July 27th, 2018. Staff Photo.

This little fly, which was just calmly hanging out on the underside of a maple leaf when it was discovered recently, is a small-headed fly belonging to a family of flies called Acroceridae.  They are all small to medium in size with a very tiny head relative to the rest of their body, which has a somewhat humpbacked appearance.  The head is comprised almost entirely of their two eyes (their eyes are holoptic, meaning they meet at the top of the head).

These flies can buzz like a bee when picked up, which can be quite startling and unnerving.  Some members of the family have a long, slender proboscis and feed on flowers.  Others lack a proboscis entirely and so apparently do not feed at all in the adult stage.  Interestingly, the larvae of these flies are internal parasites of spiders!  The flies lay their eggs in large numbers on vegetation and they hatch into tiny flattened larvae called “planidia.” The planidia wait for a passing spider to attach to, and subsequently enter into the spider’s body. The larvae pupate outside the body of the spider, often in the spider’s web (if it’s a web-spinning species of spider).

Photo of a small fly called a Small-headed fly, resting on a maple leaf (July 27th, 2018 in Etna, Maine) Photo of a small fly called a Small-headed fly, resting on a maple leaf (July 27th, 2018 in Etna, Maine)

You can learn even more about them, and find many more photos, at Family Acroceridae

Week of July 16th, 2018: Dobsonflies

Photo of a male dobsonfly beside a U.S. penny for scale purposes

A male dobsonfly (dorsal view);
Staff Photo.

photo of a male dobsonfly, ventral view

A male dobsonfly (ventral view);
Staff Photo.

Someone found this attention-getting critter pictured above in Orono this week and brought it to us (thank you, Jeff!!). It’s a male dobsonfly. Dobsonflies (genus Corydalus) are large and rather fearsome-looking insects (they raise their heads and open and close their jaws to try to intimidate, often quite successfully). They are primarily nocturnal, are more common near bodies of water (their larvae are aquatic), are active from late spring to mid-summer, and are attracted to lights. Both males and females can reach up to five inches in length, and although the rather frightening pincer-like mandibles of the male are much larger and more intimidating in appearance than are the female’s, they are so large that they afford weak leverage and are thus incapable of breaking a person’s skin. They are mostly ‘all show,’ so to speak, for impressing females, but also they are used for grasping a female during copulation. The mandibles (pincers) of the female, however, are short and stout and thus capable of inflicting a painful–but not venomous–bite (they are strong and sharp enough to draw blood).

You can find more information about them, and see additional photos of them–including one of a female–at the following page:


Week of July 2nd, 2018: Pennsylvania Wood Cockroach

A male Pennsylvania Wood Cockroach resting on an oak leaf

A male Pennsylvania Wood Cockroach resting on an oak leaf; Photo taken June 19th, 2018 in Etna, Maine. Staff Photo.

“Wood roaches,” as they are sometimes called, are a type of cockroach that live outdoors but which will occasionally find their way inside a home, shed, garage, etc. as “accidental invaders,” at which point they can become a nuisance. They feed primarily on decaying organic matter, so compost bins are a common draw for them, but their typical home in the wild is a wooded area (hence the name).  You might find one under the bark of an old log, for example, or in the hollow of a tree. They are attracted to lights at night, so that is one way in which they sometimes accidentally end up in someone’s home. Hitching a ride indoors on some firewood is another common route of entry into the home. But fear not, as they are harmless to people.

A male Pennsylvania Wood Cockroach seen in Acadia National Park; Oct. 11th, 2009.

A male Pennsylvania Wood Cockroach seen in Acadia National Park; Oct. 11th, 2009. Staff Photo.

Adult males, which are what are pictured on this page, are about an inch long and have fully developed wings compared to females whose wings are shorter and do not fully cover their abdomen. Females are a bit shorter overall as well, measuring about 3/4ths of an inch.

For more information, check out this detailed page about them which Penn State has published: Pennsylvania Wood Cockroaches

Week of June 25th, 2018: Click Beetles

Photo of a Click beetle beside a U.S. penny

An adult Click Beetle; June 24th, 2018; Etna, ME (Staff Photo)

Click beetles are ‘famous’ for their clicking mechanism that they possess. They belong to the family of beetles called Elateridae, all of whose members can ‘click,’ which, although it is used primarily as a defense to escape from or to startle a potential predator, it is also very useful in ‘righting’ itself whenever the beetle gets turned onto its back.  In hot weather, click beetles will often enter people’s houses at night through open windows and doors (they are attracted to lights), making them somewhat of a nuisance.

Photo of a Click Beetle

Another species of Click Beetle from June, 2018; Etna, ME (Staff Photo)

Most click beetles are rather small in size and dull in color. They are generally nocturnal and plant-eating, and usually of no economic significance as adults [some species of click beetle larvae, however, called wireworms, are serious agricultural pests that attack many vegetables including potatoes, onions, corn, carrots, peas, beans and melons.]

Wirewormsthe larvae of click beetles–resemble mealworms.  They are cylindrical, about 1-1/2 inches long, brownish to yellow and are rather hard-bodied (see photos below). Although some species complete their development in one year (e.g. Conoderus), wireworms usually spend three or four years in the soil before becoming adults.

a wireworm -- a Click beetle larva pair of wireworms in soil Wireworms

Week of June 18th, 2018: Whitespotted Sawyer Beetle

A female Whitespotted sawyer beetle

A female Whitespotted Sawyer Beetle (June 17th, 2018; Etna, ME); Staff Photo

If you spend any time in a forested part of the state this week, you might spot one of these somewhat fearsome-looking beetles flying about. It is a Whitespotted sawyer beetle, and if you think of it as having a body like ours for a moment, you can see that there is a rather prominent white spot located between its ‘shoulder blades’ (on the beetle’s hard wing coverings). Many people mistake sawyer beetles for the dreaded Asian longhorned beetle (ALB). However, the ALB does not have the single distinctive white spot of the whitespotted sawyer. Instead, the ALB has about 20 white spots on each wing cover. The body of the ALB is also shiny and black, compared to our sawyer beetles, and has not been detected in Maine as yet. Additionally, the antennae of the ALB are very conspicuously banded black and white. [What ALB Looks Like] (USDA)

photo of pair of Whitespotted Sawyer beetles (male on left; female on right)

Whitespotted Sawyer Beetles

The Whitespotted Sawyer beetle is a mostly minor pest of coniferous trees, especially white pine, balsam fir, and species of spruce. Other than some of the feeding done to the bark on the undersides of twigs by the adult beetles, it is regarded as a secondary pest because it is trees that are already weakened, dying or dead that the beetles utilize for their larvae. Size: Not counting the antennae, the whitespotted sawyer adults average one inch to an inch and a quarter in ‘body’ length. For more information, take a look at our page on sawyer beetles.

Whitespotted Sawyer beetle (female) Whitespotted-Sawyer-Beetle-060416b


Week of June 11th, 2018: “Hairy Rove Beetle” — Creophilus maxillosus (Linnaeus)

Photo of a Hairy Rove beetle beside a U.S. dime for scale purposes

Hairy Rove Beetle; Etna, Maine, 6/9/2018; Photo by C. Armstrong.

The first “Bug of the Week” for the 2018 season is an interesting type of rove beetle called a hairy rove beetle.  Rove beetles are in the family Staphylinidae, which is part of the “Superfamily” known as Staphylinoidea which is comprised of rove, carrion and fungus beetles.  Rove beetles often go unnoticed, even though their family is the largest of all beetle families at over 63,000 species throughout the world and nearly 400 new species being described each year!  They make up the largest beetle family in North America as well, at approximately 4,360 known species.  One reason they often go unnoticed is likely due to the fact that many rove beetles are found around decaying plant and animal remains, which people generally prefer to avoid (for obvious reasons).  The specimen featured here was in fact discovered near a compost bin full of decaying leaves, fruit, and even some lobster remains, which also made an ideal habitat for its primary prey: carrion maggots and other fly larvae.  Most rove beetles, in fact, feed on other insects and invertebrates, and their habitats on the whole are extremely varied, depending on the species.  For the most part, rove beetles have trivial importance as pests, and are collectively very beneficial given their work as predators and decomposers. 

A "Hairy rove beetle" rolled up into a defensive ball-like posture

A Hairy rove beetle demonstrating its defensive, ball-like posture. Photo by C. Armstrong.

Rove beetles are essentially harmless to humans but some of the larger ones like this one–including the hairy rove beetle, in fact–can inflict a painful bite if necessary for defending themselves.  The hairy rove beetle also employs a few other very interesting tactics for defending itself.  It can release a chemical liquid from the tip of its abdomen that it will try to wipe onto whatever might be bothering it, while at the same time rolling up into a protective ball of sorts (see photo) which has the additional effect of causing it to look dead — it superficially resembles a dead bumble bee when it is rolled up in this manner.

To read much more about the hairy rove beetle, visit the following University of Florida web page that features it in great detail: Hairy Rove Beetle

The Bug of the Week is something we like to do in order to put some lucky (or maybe unlucky) ‘bugs’ in the spotlight from time to time throughout the year.  If you have a good picture of a ‘bug’ that you’ve very recently found somewhere in Maine that you’d like to have identified and/or would be willing to have featured here as the next Bug of the Week, please email your photo to us and don’t forget to include a statement giving us permission to use your photo on our web site and how you would like to be credited for the photo.  Send your email to Jim Dill (IPM Specialist) at

Archived Bug of the Week pages:


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