Insect Diagnostic Laboratory

The giant water bug is one of the largest insects commonly encountered in Iowa. These moderately common aquatic insects live in lakes, ponds and quiet streams.  They are strong fliers, they are attracted to lights, and consequently, often are found a considerable distance from water. They may be found in the yard or street under a street lamp, or they may have crawled by accident into the house or other building.

Giant water bugs are 2 1/2 inches long and brown in color. The body is flat and elongate oval in shape but pointed at both ends. The front legs are enlarged and pincer-like with a resemblance to praying mantis front legs. A short beak is visible on the front of the underside of the head. The legs and beak combine to make the giant water bug an effective predator. They feed on other aquatic insects, snails, tadpoles and even small fish.

Giant water bugs are in no way related to, or connected with the household cockroaches that are nicknamed 'waterbugs.' The giant water bugs are harmless and interesting. They do no harm to crops, structures, people or pets and they will not reproduce or establish indoors. The worst that can happen is a painful bite if they are handled carelessly.

Special controls for giant water bugs are not necessary. Most of them die quickly if they can not get back to water.

 

 

Right on schedule! Calls and samples about bees have dominated this week.  Most homeowners asking about bees living in their house foundation or walls actually have yellowjacket wasps.  Yellowjackets are the size and shape of honey bees (about 1/2 inch long) but are bright yellow with black markings.  Honey bees are golden brown and fuzzy.

Yellowjacket wasps are social insects.  Each colony starts with a single queen in May.  The number of wasps in the nest remains very small through the early part of the summer but reaches a peak population of up to 5,000 wasps per nest by September.

Control.  If a yellowjacket nest is located where it is out of the way and not likely to be disturbed, it is best left alone.  More often, however, the nest is in a location where it can not be ignored because of the threat of being stung.  It is often the case that a nest is discovered when the yellowjackets invade the interior of the house rather than continue their usual habit of traveling out to the yard.

Nests in walls or in the ground can be destroyed by placing an insecticide dust (e.g., Boric acid, Sevin or permethrin) in the nest entrance during the night.  Wear protective clothing and approach the nest with caution.  Do not shine your flashlight directly into the nest opening. Dusts generally provide better control of the colony than liquid sprays.

A hand duster or similar application device makes it possible to dispense several puffs of the dust into the nest opening.  Use a dry, empty liquid detergent bottle filled with no more than 2 tablespoons of dust and shaken before dispensing in lieu of a commercial duster.  Control will usually be achieved within a few days.  Retreat after 2 or 3 days if necessary.  Do not plug a nest opening in a house wall until you are sure all activity within the nest has stopped.

 

 

Imperial moths are members of the wild silk moth family, which includes the Luna and Cecropia moth.  Imperial moths are very large moths with beautiful yellow and almost purplish coloration.  Imperial moths spend the winter as pupae under leaf litter and loose soil. 

In the last few weeks we have received many reports from people who are finding these large caterpillars crawling on the ground.  This is because the caterpillars have dropped from the trees and are searching for a safe spot to molt into the pupal stage. 

If you would like to see the moth next year you can keep the caterpillar.  Place the caterpillar in an aquarium with a couple inches of soil and some leaf litter.  The caterpillar will crawl around and eventually bury itself and molt into the pupal stage.  This will take a while, so try to avoid the temptation to dig it up and check on it for a couple of weeks.  
Store the aquarium outdoors for the winter, so it stays cold.  Then in the spring make sure there is a branch propped in the cage for the newly emerged moth to climb up on to expand its wings.  The moth should emerge sometime in late-May or June.

Though house centipedes are found both indoors and outdoors it is the occasional one on the bathroom or bedroom wall, or the one accidentally trapped in the bathtub, sink, or lavatory that causes the most concern.  However, these locations are not where they normally originate.  Centipedes prefer to live in damp portions of basements, closets, bathrooms, unexcavated areas under the house and beneath the bark of firewood stored indoors.  They do not come up through the drain pipes. 

House centipedes feed on small insects, insect larvae, and on spiders.  Thus they are beneficial, though most homeowners take a different point-of-view and consider them a nuisance.  Technically, the house centipede could bite, but it is considered harmless to people.

House centipede control consists of drying up and cleaning, as much as possible, the areas that serve as habitat and food source for centipedes.  Residual insecticides can be applied to usual hiding places such as crawl spaces, dark corners in basements, baseboard cracks and crevices, openings in concrete slabs, under shelves, around stored boxes, and so forth. 

 

 

The cecropia moth caterpillar is the largest larva found in Iowa and is commonly seen in late summer throughout the state.  Larvae may be seen feeding on the trees and shrubs where they have spent the summer, or they may be found "wandering" across lawns, sidewalks and driveways.

The cecropia caterpillars feed on a wide variety of trees and shrubs, including wild cherry, plum, maple, willow, boxelder, apple, crabapple, lilac, walnut, elm, birch and poplar.  No control is needed for cecropia moth caterpillars. They cause very little harm to ornamental plants and encouraging their existence provides the pleasure of seeing the moths in the spring. 

If you want to raise cecropia moths, keep caterpillars in a large container along with an adequate supply of fresh foliage from one of the plants mentioned above.  A stick wedged diagonally through the rearing container will facilitate the formation of the cocoon. Cocoons that are raised or discovered outside should be left in the winter environment until late April.

 

 

For the last few weeks many of us have been finding strawberry root weevils wandering around our houses.  This is a very common insect and is found throughout Iowa. Adult strawberry root weevils are brown-to-black and about 1/3-inch long. They have a pear- or light bulb-shaped body and long elbowed antennae.  Strawberry root weevil larvae live in the soil and feed on the roots of strawberry plants, evergreen trees and shrubs.  In mid-summer, the adults emerge from the soil.  They feed on plant foliage but cause no significant damage to the plants.  They would go unnoticed except that large numbers regularly wander into houses by mistake as "accidental invaders."   These are not damaging to the house or furnishings.  They do not harm people or pets, and are a nuisance only by their presence.

 

 

 

Grease ant is a name commonly used for one of the smallest ants found in homes in .  These ants are technically known as thief ants.  They are very small; only l to l.5 mm (1/16th inch) long.  They are smooth and shiny and may be yellow to light or dark brown.  Though they will eat almost anything, these ants prefer to eat grease, fats and meats.  Grease ants form a trail from the food to the nest and the moving columns of ants can be noticed upon careful inspection.

Most available ant baits must be mixed with a grease or oil (vegetable, corn, fish, etc) to make them attractive to grease ants.  Start with a 1:1 mixture and see if the ants are attracted to the bait, if not try more oil, or a different kind of oil.  Once mixed, the bait can be placed on small squares of paper or the non-sticky side of small masking tape strips.  Use baits with care.  Make sure the bait is out of the reach of children and pets.  When ant activity has ceased, carefully dispose of the remaining bait.