Hi,

Your ants are most likely carpenter ants.

Carpenter ants, Camponotus sp. (Hymenoptera: Formicidae).

Carpenter ants are one of the largest and most common ants in Michigan. Unlike termites, they only nest in wood and do not eat it. Outdoors, they commonly nest in hollow trees and stumps. Finding them indoors during the summer does not necessarily mean they are nesting in your house, they may just be coming in from outside.  However, the presence of carpenter ants in homes during the winter months, when it is too cold outside for ants to be active, is a very strong indication a colony of carpenter ants exists inside the building.  When they do nest indoors, they prefer an enclosed space that remains wet or damp, more or less, or a permanent basis. Carpenter ants are attracted to excessive moisture conditions around windows, doors, showers, bathtubs, dishwashers, leaky pipes and drains, and under leaky roof shingles or roof vents.  They have also been found in dry areas such as hollow-core doors and false beams, and blueboard foam insulation.   

The presence of winged carpenter inside the home during the summer, does not by itself, mean you have a carpenter ant nest in your home.  Winged ants are the reproductive forms of the colony and usually issue from the colony in late spring.  They drop their wings soon after mating and begin to search for a suitable nesting site.  They commonly enter structures but only rarely do they succeed in finding a nest site and most winged forms die before establishing a nest.  

The best method of controlling an indoor colony of carpenter ants is to locate the nest and treat it directly with a persistent insecticide registered for indoor use.   Insecticides labeled for this use include cyfluthrin (sold as Bayer Advanced Home Insect Control for homeowners or Tempo for commercial applicators), Ortho’s Home Insect Defense, or similar products.   Most importantly, be sure to make any repairs, if necessary, to keep the area dry.   

Another approach that is gaining strength in the pest control industry is to spray all possible entry points on the outside of the building (where sills and foundations meet, around doors, windows, vents and utilities) with fipronil (sold as Termidor SC).  Fipronil forms a non-repellent barrier that the ants cannot detect.  They pick it up and spread it through the colony.  Termidor is not widely available but it can be purchased over the internet or at John Deere Landscaping (formerly Lesco’s).  Termidor cannot be used inside homes and other buildings.  

Commercially prepared ant baits are available but I don’t know how effective they are controlling carpenter ants; they are probably more effective in the winter when the ant’s favorite foods are not available.   One internet supplier of carpenter ant baits is doyourownpestcontrol.com.  They sell at least three bait products for carpenter ants.  I recommend trying the Maxforce Carpenter Ant Bait Gel first and see how that works before purchasing one of the others.  See their carpenter ant baits at: http://www.doyourownpestcontrol.com/carp.htm  

Finding the nest can be difficult since many of the ant’s favorite nesting sites are inaccessible. Begin looking in the rooms where the greatest numbers are found and observe where they go or come from.  Carpenter ants are nocturnal and are most active at night.  Carpenter ants are very tidy housekeepers and quickly remove wood shavings, food debris and dead co-workers from the nest area.  In many cases, this nest debris accumulates in basements beneath the nest area, so look for accumulations of coarse sawdust and dead ants along and on top of basement walls and in cobwebs.