The Invasion of Ground Beetles

The Mid-Atlantic states are reporting large numbers of the large ground beetle, Calosoma scrutator landing on the exterior walls of buildings.

One coffee shop in Fairfax, Virginia, temporarily closed due to the large number of the beetles on the exterior and interior of the store.  Calosoma scrutator is also known as the fiery searcher or caterpillar hunter.  It is one of the prettiest and striking colored ground beetles found throughout North America and not uncommon in the Midwest.  Adults can reach 1.5” in length.  The wings are bright green with a red border.  The pronotum or area behind the head is blue.  The adult and larval stages of this beetle will feed primarily on caterpillars but will also feed on other insects.  We are not sure why there are such large numbers of the beetles showing up this year.  Although larger numbers have been reported on the east coast, there is evidence these beetles are making their way into the Midwest with sightings in the St. Louis area being reported.  The beetles are active at night and attracted to lights.  Busch stadium in St. Louis reported large numbers which certainly has sufficient lighting to attract these beetles.  We don’t believe they are Cardinal fans.

Control Methods

From a control standpoint, installing the right type of exterior lights can be helpful in reducing the number of insects around the building.  Low pressure sodium vapor lights are less attractive to insects than mercury vapor lights and should be utilized to reduce insect pressures especially if the lights are installed directly on the building.   If mercury vapor lights are used, they should be installed at the property perimeter or installed on posts aimed at the building.  Utilizing the more attractive lighting away from the building can help pull the insects away from the building.  In addition to proper lighting, exclude beetles by keeping doors closed when not in use.  If doors are left open for ventilation purposes, use screens to prevent pest entry.  Make sure windows and vents are also suitably screened to exclude insects.

Installing the right type of exterior lights

• If installing lights directly on the building, use low pressure sodium vapor lights, which are less attractive to insects than mercury vapor lights.

• If installing mercury vapor lights, install only at the property perimeter or on posts aimed at the building.

Using screens to prevent pest entry

• Keep doors closed when not in use. If doors are left open for ventilation purposes, use screens to stop beetles from entering.

• Windows and vents should also be suitably screened to exclude insects.