Bastiaan M. Drees, Professor and Extension Entomologist
Velvet ants commonly are encountered in arid, sandy areas of Texas. Although related to wasps, the wingless females resemble ants and have a dense coating of velvety hair. Males have wings and actively fly. They are in the family Mutillidae in the order Hymenoptera that also contains ants, wasps, bees and sawflies.
Krombein et al. (1979) list 30 genera of Mutillidae in found in North America. Of these at least 84 species are possibly considered to be “velvet ants” and occur in Texas. These species are from the three genera: Timulla – 15 species, Ephuta – 9 species, and Dasymutilla – 60 species. Many other species are listed for this family of insects, but most are not normally thought of as the day-active (diurnal), fuzzy or hair-covered, and colorful “velvet ant” species. The most commonly encountered and largest species is known as the cow killer, Dasymutilla occidentalis comanche Blake (Fig. 1).
Figure 1. The cow killer, Dasymutilla occidentalis, adult female.
Figure 2. Another species of “velvet ant” (Hymenoptera: Mutillidae)
Biology
Velvet ants are solitary wasps. Immature stages or larvae feed externally on the prepupal or pupal stages of ground-nesting bees, other wasps and some flies and beetles. The wingless females actively search for hosts on which to deposit eggs. The host is attacked after its cocoon has been spun, or the puparium formed. Upon locating a suitable host, the female penetrates the cocoon or puparium with its long ovipositor (which can also function as the stinger) and deposits one or two eggs.
Eggs hatch and young larvae feed on the host, devouring it. After feeding, the velvet ant larva spins its own cocoon within that of its host. Over-wintering occurs as the prepupal stage inside the host’s cocoon. Developmental times vary between species and in response to various environmental conditions.
Upon emerging as adults, winged males fly in search of mates. The wingless females attract males of their own species using specific sound produced by a rasping structure located between their second and third abdominal segments. Mating lasts for only a few seconds. Males not searching for females are often found visiting flowers in search of nectar. They do not live as long as the wingless females.
Importance
Females spend much time in sandy areas searching for hosts and may be encountered at close range by adults and children. The females are capable of stinging repeatedly. The stinger is long, and the sting is reportedly quite painful–perhaps the reason that the large common species is called the “cow killer”.
People are most often stung by velvet ants on the foot while walking in infested areas without proper footwear. The intensity of pain and reaction to the sting will vary according to the sensitivity of the person stung.
Luckily, these are solitary creatures and the possibility of being stung by a number of these insects at one time is unlikely.
No one has documented the importance of velvet ants as parasites of other insects. Ground dwelling bees, often important in the pollination of some crops such as alfalfa, are known to be hosts for velvet ants. Other species are reportedly pests of white grub parasites, a condition known as hyperparasitism. In each of these different examples, velvet ants can be considered either beneficial or pestiferous depending upon the host species.
Control Measures
Chemical control of velvet ants is rarely justified. The best methods for coping with velvet ants are: 1) the education of youngsters not to (or carefully) handle these insects and 2) wearing shoes in infested areas to avoid accidental encounters. These insects are very hard-bodies and difficult to crush by stepping on them. Also, their long stingers (modified egg-laying structure or ovipositor) are flexible and can inflict a painful sting even when the end of the abdomen is not directly contacting skin.
Occasionally, numbers of velvet ants occur in certain areas such as gardens or underneath houses, trailers or other structures raised from the ground. In these cases, the best control tactic is to eliminate ground-nesting wasps or bees on which immature velvet ants feed. Contact insecticides with label directions for “digger wasps” can be used to attempt to control such insects. For information on controlling the hosts, see L-1828 “Paper wasps, Yellowjackets and Solitary Wasps” (http://tcebookstore.org/tmppdfs/22109649-L1828.pdf. Individual velvet ants can be killed by crushing or by using directed sprays of household aerosol formulations with “crawling insects” or “wasp nests” that often contain synergized pyrethrins or synthetic pyrethroids such as resmethrin are available for wasp control.
Literature cited
Krombein, K. V., P. D. Hurd, Jr., D. R. Smith, and B. D. Burks. 1979. A Catalog of Hymenoptera in North America North of Mexico, Volume 2. Smithsonian Institution Press, Washington, D. C. (Family Mutillidae, pages 1276-13142209 pages.
Acknowledgments
The author wishes to thank Dr. Jerry Cook, entomologist with Sam Houston State University, and Ed Riley, Assistant Curator for the Texas A&M University Department of Entomology for their review and helpful comments in the development of this fact sheet.
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