Insects Found En Masse Inside House, St. Clair River

Asked July 2, 2020, 8:48 AM EDT

Hello, I found and killed about 100 of these inside on the sill of several of our windows this morning. Recent history of the house includes an in wall yellow jacket nest that was exterminated last fall, and several small common ants seen by the kitchen sink last week. Not sure what these are, but I'd rather they be outside. Any help on identification?

St. Clair County Michigan

3 Responses


Those look like winged crobat Ants, Crematogaster species (Hymenoptera: Formicidae).

Acrobat ants get their common name from their habit of raising their abdomen over their head and thorax. The workers are known to bite aggressively and to give off a repulsive odor when alarmed. In nature, colonies may nest in exposed soil, under stones, stumps and old trees. They occasionally become pests by invading homes where they are known to nest in woodwork and foam insulation, and infest household foods. They feed on live and dead insects, and they tend aphids for their sugary excrement known as "honeydew." In homes, they show a slight preference for sweets and meats or other high protein foods.

Winged forms or reproductives usually appear in the fall of the year. When these appear inside homes, it is a good indication there is a nest of acrobat ants located inside the home.

Howard, thank you for your expertise and impressively quick response. These were found in our house on the St. Clair River built in 1925, and if I'm reading right would be the winged reproductives? Assuming there is a nest in the house, can you recommend any best practices for prevention, location, and removal? Thank you again!

The best method of control is to locate the nest and treat it directly. They like hollow core doors and wall voids. Begin looking near where you see concentrations of the ants.

Good luck.