Insect Diagnostic Laboratory

The past few weeks in the clinic we have been receiving many calls and insect samples. Some of the most common insect concerns are cicada killer wasps, ants in the house, and various caterpillars eating plants. A couple of interesting beetles have also starting popping up in homes, the imported longhorned weevil and the strawberry root weevil. These accidental invaders are harmless outdoor insects, but can be quite a nuisance when they enter your home in large numbers. The strawberry root weevil is a brown to black beetle about 1/3 of an inch long. The body is bulb shaped and they have long elbowed antennae. The imported longhorned weevil is smaller and gray colored. The larvae of the imported longhorned weevil live in the soil and eat the roots of many different plant species. The larvae of the strawberry root weevil also live in the soil and feeds on the roots of strawberries and evergreen trees and shrubs. Luckily, these larvae do not cause significant damage to plants and no control of the larvae is necessary. The adults accidentally crawl into homes, so the best prevention is to seal cracks and gaps that a crawling insect would come across. Spraying insecticides outside around the foundation may also help. Once the beetles are indoors the best remedy is to vacuum them up.

This week we began to receive calls about cicada killer wasps. Cicada killer wasps are large (up to 2 inches long), black and yellow wasps with rusty colored wings. Cicada killer wasps are solitary, only one wasp per nest. The female wasp digs a whole where she lays her eggs on paralyzed cicadas that she catches. Although cicada killers are solitary it is common to find multiple nests in a single area. Cicada killers may look big and scary, but they are a non-aggressive wasp and seldom sting people. In general it is best to leave nests alone, however, removal is justified if a nest is located in a high traffic area (along a sidewalk or near a porch). Ground nests of cicada killers can be destroyed by placing an insecticide dust (e.g., Sevin garden dust) in and around the nest entrance during the night. The dust particles will adhere to the wasps as they come and go from the nest. Cover the nest opening with a shovelful of soil after all activity has stopped.

Finally, we received two reports of Imperial moths around the Iowa State campus in the last week. Imperial moths are a wild silk moth, in the same family as Luna moths and Cecropia moths. Imperial moth caterpillars feed on a variety of hardwood trees and pupate in the soil. The moths emerge the following year. Like all wild silk moths, the adult moths do not eat. The adult moths live only long enough to mate and lay eggs to start the next generation. Imperial moths are attracted to lights at night, where they will remain throughout the next day. Unfortunately, it is often open areas, like parking lots, that have lights on all night. Remaining in these areas throughout the day leaves the moths vulnerable to traffic and to birds.

Samples this week have included one of the largest insects in Iowa, the dobsonfly (Corydalus, spp., Neuroptera: Corydalidae). This is also one of the largest aquatic insects in North America. Adults measure two to four inches from the front of the head to the wing tips. Dobsonflies have a short, soft abdomen under their large, wrinkled, brownish-gray wings that are held rooflike over the body. The antennae are long and threadlike.

Enlarge	Dobsonfly near Evansdale, Iowa.
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The last two weeks we have getting many reports of mosquitoes. Mosquitoes take about a week or two to develop from eggs to adults. The rain we received in May provided ample breeding areas for the mosquitoes. The larvae develop in water with some organic matter. Around homes they are often developing anything that will hold water, such as birdbaths, pet bowls, pails, old tires. Mosquitoes will develop in ponds, but often there are fish and other predaceous insects that keep populations in check.

For the homeowner, the best thing to do is avoid being outdoors at dawn and dusk when the female mosquitoes are most actively feeding. Also, use a mosquito repellent containing DEET.

To control the larvae you can reduce the number if items in your yard that will hold water. Be sure to replace water in bird baths and pet bowls weekly, or when it is very warm every 4 days. There are products available containing a Bt bacteria that are effective at controlling mosquito larvae if the water cannot be easily replaced. These products are available in most stores that carry insect control products.

It has been a busy few weeks here at the Insect ID Clinic. We have been getting many reports of boxelder bug nymphs. They are usually seen in groups, are red and tear shaped. The nymphs do not have fully formed wings like the adult boxelder bugs do, and often there are different stages of the nymphs, so there will be a whole range of sizes.

Some of our ant species also seem to be swarming. Swarmers are winged ants that leave the colony to mate and establish new colonies. This is a difficult task because a new queen will have to reproduce a whole new colony by herself. This is why an established colony will produce many winged ants in hopes of establishing at least one new colony.

Wolf spiders are also accidentally wandering indoors. Wolf spiders are large and somewhat intimidating spiders. Luckily, they are harmless and the best thing to do when they wander indoors is capture them and return them to the outdoors.

Black flies have been bothering people this past week. These small flies are commonly called turkey or buffalo gnats. The larvae are found in fast moving streams where they feed on algae and other organic matter. The adults emerge in the spring. Some species of black flies have painful bites that can cause the skin to swell and itch. Unfortunately, mosquito repellents don’t seem to deter them much. However, the adults live only a few weeks and there is only one generation a year, so they should be gone soon.

We are also receiving many samples of garden insect pests. With the nice weather everyone is in their gardens noticing the holes in their plants!

This week the wet weather has brought out the springtails. Springtails are small, harmless insects that feed on decaying organic matter. They often accidentally wander into homes. They get their name from their ability to jump about when disturbed, so they are often mistaken for fleas.

Ant mounds have been appearing overnight this week. To avoid some of the worst ant mounding, regularly rake or "wash" (with a water stream from the garden hose) ant mounds that appear above the grass tops flat, especially during periods of prolific ant nesting activity (such as during periods of wet spring weather). If necessary, you can spot treat anthills with an insecticide labeled for ants outdoors. Read and carefully follow instructions on the insecticide label. Overall lawn treatments specifically for ant colonies are seldom necessary.

The May or June beetles (Phyllophaga sp.) are also starting to appear around lights at night. May or June beetles are the adults of the true white grub. The adults gathered at lights can be an annoyance, so the best thing to do is leave outdoor lights off if possible, or replace white light bulbs with yellow light bulbs. The smaller, but similar, northern masked chafer, Cyclocephala borealis, will also start appearing soon. The larvae of the northern masked chafer are called the annual white grub. These beetles that are also commonly called June bugs by many of us, although they are beetles, not bugs, and a different species than the June beetle.