We came across a very unusual pine tree ant infestation. The resident of a house in Sonora, on Villas Lane, had been gone a week, and when he came back, found his kitchen floor covered with a fluffy, dusty material.
Examination revealed an infestation by pine tree ants, and oddly, these ants were attacking the insulation around a couple of kitchen appliances, an oven and a dishwasher. Typically these ants excavate in soft wood, such as rotted parts of pine trees, and Celotex ceiling insulation. I’d not seen them try to nest in appliance insulation.
The ants had a handy food source, about 20 feet from the appliances: a hummingbird feeder on the front porch.
23 June 2020
We had an unusual occurrence of velvety tree ants infesting a ceiling, inside a home, in the Sonora area. I have seen this type of infestation in the past, but it is rare, and we were able to document this case. Most commonly, it is pine tree ants, Liometopum luctuosum, that we see exhibiting this “nesting in the ceiling” behavior. But this one was velvety tree ants (confirmed by Dr. Philip Ward), and the velvety tree ants were there in large numbers.
Ron Walther reported that the ants were in the open beam ceiling, and were dropping larvae down onto the sofa and floor beneath.
After the application by technician Erik Brians, there were piles of dead and dying ants.
Pine tree ants, liometopum luctuosum, are a native ant that loves to nest in large pine trees that have some decay in them. Houses prove to be a suitable, or additional, place to nest. These ants excavate into lumber to create room for the nest, and they will carry the sawdust and throw it out. The sawdust can accumulate in large piles, under nesting sites. These photos of the sawdust were taken by Jose Rodriquez, at a residence in Forest Meadows, Calaveras County, California, October 2017.
A house in the Tuolumne City area had a long-term infestation of pine tree ants, Liometopum luctuosum. Native to the area, these ants like to nest in pine trees. In this case, some wall studs worked just fine. Photos by Jon Shattuck. Video by the home owner.
The images show the wall studs after our repair crew opened the wall.
Jon Shattuck collected samples of the debris from a pine tree ant (Liometopum luctuosum) nest. The contents are variable and represent dead ants, both adults and larvae, and the food they have been collecting. The sample came from near a nest in a rarely visited guest house in the middle Camp Road area of Twain Harte, 7 March 2017.
Click to enlarge.
This video taken by Ryder Richards in 2015, in Arnold California, shows pine tree ants, Liometopum luctuosum, in the ceiling of a house. You can hear the noise they make. It appears the ants excavated their way through the Celotex insulation, and the rift is in the egg storage area of the nest, as they are dropping eggs and larvae through the crack.
Here is an article by Jim Tassano, published in the Summer 1987 issue of the Voice of the Pest Control Operator of California. This is possibly the first article identifying liometopum luctuosum, the pine tree ant, as a structural pest.
Pine tree ants, Liometopum luctuosum, are common in the 2000-4000 foot elevation range in Tuolumne and Calaveras counties. These ants prefer to nest in large pine trees. The colonies get quite large.
A Super Colony? Pine tree ants will almost suddenly appear in spring, trailing from pine tree to pine tree. I (JT) have followed trails from tree to tree, and basically see a web of interconnected trails. It seems they form some sort of super-colony. As mentioned in the previous post on pine tree ants, I once took some pine tree ants from Pine Mountain Lake, in Groveland, to Columbia College, in Columbia, during early spring when the ants are trailing out to set up spring and summer nests. I placed the Groveland ants along side of a large trail of Columbia ants, and the Groveland ants immediately joined the Columbia ants’ trail. This observation makes me wonder if they are not all part of the same super-colony.
In their spring efforts to set up nesting areas, pine tree ants often move into the ceilings and walls of houses. Homes built with Celotex insulation are common targets, with the ants tunneling through the insulation to make nests, and throwing out the insulation, into piles on the floor of the house or cabin.
pine tree ant, Liometopum luctuosum. Picture by Jose Rodriguez.
pine tree ant, Liometopum luctuosum . Picture by Jose Rodriguez.
Click on an image to enlarge it.
The pine tree ant, liometopum luctuosum, is a common pest species in the mid-elevations areas, common in Groveland, Sonora and Columbia up through the Crystal Falls elevation and in Forest Meadows through the Arnold area. The species prefers to nest in large ponderosa pine trees, but will also build nests in houses.
The pine tree ant is similar to the odorous house ant in several ways and is sometimes confused with them. Both are uniformly darkish brown and both gives a noticeable odor when crushed. The body size of pine tree ants ranges from that of the odorous house ant to about twice that size, in the same colony. You need to look at a number of specimens to assess body size and you should be able to spot the size differences between individuals in a single colony. OHA have little noticeable size variation like pine tree ants do. And unlike the OHA, pine tree ants nest in ceilings, kick out piles of sawdust and can form very long networks of trails. Trails sometimes follow along telephone lines, leading ultimately to a branch of a remote pine tree.
Houses serve as nesting sites
The species becomes a noticeable pest when it sets up satellite colonies in houses, commonly in ceilings that use ceiling tiles like Celotex. The materials are similar from the ant’s point of view, I presume, to the rotting heartwood of a mature pine tree. The ants can easily excavate tunnels and chambers and store developing larvae there. The excavated material is often discarded by the ants and forms piles of sawdust under the areas of attack.
These ants appear to overwinter mainly in very large pine tress. In spring the ants start trailing between large pines and the houses they have selected for nest sites. I have tracked these ants and at peak trailing, it appears that there is no end to the inter-connectiveness of the trails. I once took some worker ants from a trail in Pine Mountain Lake to Columbia College and placed the ants in a trail there. The relocated workers instantly joined the trailing ants. Could it be that all pine tree ants form a sort of super-colony?
Also, following the trailing ants, every once in a great while you might get lucky to see nest commensals (other species of insects that live as nest parasites in the colonies) also walking in the trail, just like the workers.
One feature of pine tree ant infestations is the accumulation of piles of sawdust beneath nesting areas. These photos, by Jon Shattuck (28 August 2017, Sonora area) are characteristic. These piles can often be found inside homes, where the sawdust falls onto tables, furniture or floors. In this case, the debris fell outside, on the deck. See also Pine Tree ants (2)