Ecology of Dorymyrmex flavus McCook (Hymenoptera: Formicidae) in central Texas, including aspects of competition with Solenopsis invicta Buren (Hymenoptera: Formicidae)

Abstract

Dorymyrmex species, commonly known as "pyramid ants," are found throughout the United States, but are most common in the South. They occur in open areas, without a closed canopy overhead, and prefer to nest in sandy soils. Dorymyrmex flavus McCook is one of six species found in Texas. Similar to the other Dorymyrmex species, it is an opportunistic omnivore. It feeds on honeydew and other arthropods, both by hunting and also scavenging. The colony sizes in central Texas are much smaller than those of the same species found in Florida, with numbers of less than I 000 workers in late summer and early fall. No size castes exist among workers, thus this species is monomorphic. This species swarms from the summer months well into the fall season, as indicated by the presence of winged males. The nests occur in open areas and sandy substrates, such as Zulch Fine Sandy Loam. Colonies are polydomous, and build the nest to a depth of a least 61 cm. Despite possessing no sting and existing in small colonies, D. flavor continues to thrive in,Yolenopsis invicta Buren infested areas. This is accomplished by a combination of several factors. First, D..flavus is an effective defender of the nest, in which it uses its mandibles to kill invaders. Second, it may possess an ability to seal off tunnels and escape, in the event of an invasion. Third, the fact that D. flavus occupies soils that are not well suited to S. invicta keeps the colonies somewhat spatially separated, limiting the stimulus for a large scale invasion. Fourth, D. flavus colonies often occur in clumps, increasing the numbers to defend a territory. Lastly, D. flavus exhibits extremely aggressive behavior toward newly mated S. invicta queens, which prevents new ,S. invicta colonies from forming nearby, thereby lowering the threat of competition.