"The Thief Ant" (Solenopsis molesta)

According to some experts, the thief ant, Solenopsis molesta, may not be a definite species. The thief ant is probably a conglomeration of many similar species which have been confused since the original description of the species. Currently taxonomic experts are revising the Solenopsis group which should result in some clarification in identifying members of the genus. In addition, due to the many species which can be mistakenly identified as thief ants, its role as a pest may be questionable. Specifically, it has probably been blamed for more problems than it has actually caused. The behavior of the thief ant indicates it is a rather beneficial since it feeds on the immature stages of ants and other insects.

This species is generally distributed throughout the United States. It nests in cracks and crevices in cupboards or walls. It is a very persistent creature and is controlled with much difficulty.

Thief ants often live in association with the nests of larger ants. They enter the other ants' nests by means of tiny passages that are too narrow for the larger ants. The "thiefs" move about the chambers and kill and eat the immature forms of the host ant and for this reason may be considered beneficial. They are also predacious on many insects.

The thief ant is attracted to greasy materials such as cheese and animal matter. Some individuals are of the opinion these ants are not attracted to sweets, but McCulloch and Hayes (1916) state they feed on sweetened food in the house.

Eckert and Mallis (1937) noted this ant often feeds "upon dead rats and mice and thus might convey disease-inducing organisms to human food." The ants also may serve as intermediate hosts for poultry tapeworms because the workers have been seen carrying egg segments into the nest.

Thief ants are of some importance to the poultry man since they attack young chicks. At times the thief ants are responsible for injury to sprouting seeds and vegetables. These ants are believed to hollow out the seeds for the oil content.

The eggs of this ant have an incubation period of 16 to 28 days. The queens lay 27 to 387 eggs, generally averaging about 105. During the summer, the larval stage may be as short as 21 days. However, the larval stage may be greatly extended when the ants overwinter as larvae. The prepupal stage extends two to 11 days during the summer and the pupal stage is 13 to 27 days. The larvae are fed upon regurgitated food, insect parts and small pieces of seed. The nests occur in a great variety of locations outside the home, particularly under rocks, MacNamara (1945) notes the queens in their mating flights may carry some of the tiny workers and it is possible they latter may aid in founding new nests.

There may be many queens in one nest. The queen, which is about 1/5 inch long, is considerably larger than the worker. The winged males and females have been observed in flight during June in Los Angeles.