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Extension Entomology

Tag: life cycle

Wheel Bug: Be On The Look-Out For This Distinct “Bug”

by–Dr. Raymond Cloyd

If you have spent any time outdoors in the last month, you may have noticed a very distinct, grotesque looking insect on trees, shrubs, or near homes. This insect is the wheel bug (Arilus cristatus), which is common, and widely-distributed throughout Kansas and the USA. Wheel bugs, also referred to as assassin bugs, are predators that prey on insect pests. However, both the nymphs and adult can inflict a painful bite when handled by humans.

Adult wheel bugs are 1.0 to 1.25 inches long, robust with long legs and antennae, and have a stout beak and large eyes on a narrow head (Figure 1).

newFigure1WheelBugsMatingMaleonTopofFemale

 

Figure 1: Wheel Bugs Mating Male on Top of Female.
Figure 2: Wheel Bugs with Crest or Wheel on Thorax.

They are dark-brown to gray in color. The adults possess a wheel or crest with 8 to 12 protruding teeth-like structures (tubercles) on the thorax that looks like a cogwheel (Figure 2). Wheel bugs have two long, slender antennae that are constantly moving or weaving around. Females are typically larger than males. Females lay eggs that resemble miniature brown bottles with white stoppers (Figure 3).

newFigure3WheelBugEggs

 

Figure 3: Wheel Bug Eggs.

The eggs are laid in clusters of 40 to 200, and are glued together and covered with gummy cement, which protects the eggs from weather extremes and natural enemies (e.g. parasitoids and predators). The egg clusters are primarily located on the trunk or branches of trees or shrubs. The eggs hatch into nymphs that are bright red in color with black markings. The nymphs do not have the wheel or crest. The life cycle, from egg to adult, may take 3 to 4 months to complete. Wheel bugs are active day and night. They are very shy and tend to hide under leaves. The wheel bug has one generation per year and overwinters as eggs.

Wheel bugs are voracious predators and feed on a wide-variety of insects, including caterpillars (Figure 4), beetles, true bugs, sawflies, and aphids. Unfortunately, wheel bugs will feed on beneficial insects such as ladybird beetles and honey bees.

newFigure4WheelBugReadyToAttackCaterpillar

 

Figure 4: Wheel Bug Ready to Attack Caterpillar.

The mouthparts are red-brown in color and resemble a tube or straw that is located underneath the head (Figure 5) and extends out when ready to “stab” prey. Wheel bugs paralyze prey with their saliva, which contains a toxic substance that immobilizes prey within 30 seconds. In addition to feeding on insects, wheel bugs are cannibalistic, and will feed on each other.

newFigure5WheelBugsWithMouthUnderneathHead

 Figure 5: Wheel Bugs with Mouth Underneath Head.

Millipedes On-The-March?

–by Dr. Bob Bauernfeind

While I am not saying that this will happen, the excessive spring rains might be conducive to promoting movements of massive populations of millipedes.  Millipedes in of themselves are harmless (do not bite, sting transmit diseases), and in fact are beneficial in their natural role as decomposers (feeding on dead organic matter).  It is the sudden presence of large populations moving in and about residential properties that can be disconcerting.

Millipedes are elongated wormlike arthropods.  They can be differentiated from centipedes by virtue of the number of legs per body segment.  Whereas centipedes have a single pair of body legs per segment, millipedes appear to have 2 pairs per body segment.  I use “appear” because what appears to be a single body segment actually is comprised of two fused segments, each with a pair of legs.

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The two most common body forms for millipedes common are cylindrical and plated (flat-backed).  Cylindrical millipedes are sometimes referred to as “wireworms” (not to be confused with “true wireworms” – the larvae of click beetles), and when viewed from above, their legs are somewhat hidden due to their ventral position.  The legs of flat-backed millipedes are more highly visible as they project outward from beneath the extended plate.

The life cycle of millipedes extends over a period of years.  Depending of conditions, development from egg to adult may require 2 – 4 years, with adults living additional years.  Thus over time, millipede populations build up (especially) in heavily wooded areas which satisfy their preference for shaded and moist environments where they primarily feed on decaying organic matter, notably leaf litter.

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For reasons unknown, countless numbers of millipedes move/march in droves.  They make their presence known when they invade yards and homes.  This accounts for reports the reports of “worm invasions”. And although millipedes are harmless to people and pets, they may enter garden areas and sometimes feed on tender plants.

The most common complaint, however, is their disconcerting presence. They are mostly observed around daybreak when massing on sides of buildings, patios/decks, driveways and sidewalks and decorative rocks.  Especially on hot sunny days, they rapidly disappear as they seek protective shelter/cover, only to re-emerge during the ensuing evening.

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Frustrations arise when attempting to control millipedes.  Again, millipedes seek “hiding places” —- any available crack or crevice in the soil, under bark mulch, under landscape stonework, gravel, plastic ground cover, leaf litter in and around homes.  Elimination of these protected sites is impractical-to-impossible.  Insecticides registered for use as perimeter treatments will eliminate those millipedes in the target area.  However repeated applications will be required for the duration of millipede invasions.  Another nuisance factor:  the dead millipedes will have to be swept up and disposed of.  The best news is that millipede activities stop as suddenly as they began!

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