SPECIES PROFILE OF THE HARVESTER ANT
By John V. Richardson Jr.
Figure 1. California Harvester Ants
Courtesy of http://commons.wikimedia.org/wiki/Image:Pogonomyrmex_californicus_2003-05-19.jpg
Popular Name: Harvester Ant (Buckley, 1867)
Latin Binominal: Pogonomyrmex californicus
Family, Sub Family: Formicidae, Myrmicinae
Identification/Description: small and reddish brown (Taber, 107). Noted for its large, finely grooved head with “beard, the long hairs on the chin function to carry sand or soil when the ant is excavating” (Hogue, 327). Elbowed antenna (Castner, 162).
Length: Generally, ¼ inch or 6mm (Hogue, 128); but, ½ inch for larger species. May weigh 6.5-17 milligrams.
Immature Stages: “Larvae of ants are maggot like, with translucent skin” (Taber, 29).
Life Cycle: “Aging workers lose weight and their teeth wear down to nubbins (Taber, 68 citing Porter and Jorgensen, 1981).
Food: during the day, seeds including California poppy bush, “which actually benefits when its seeds are trundled off” (Taber, 42) as well as the poisonous [Datura or] jimson weed (Taber 43, citing Snelling and George, 1979). This kind of mutualism is
In addition, termites (Taber, 35), bee pollen and other insects including caterpillars. Optimal soil temperature for foraging is 68-122 degrees (Taber, 40 citing Lavigne, 1969); however, they can forage in 130 degrees, but at 140 will most often be found in vegetation above the nest (Taber, 15 citing Whitford and Ettershank, 1975). Maximum distance travelled is 160 feet from nest (equivalent to 10 mile trip for human, Taber, 41).
Food Plants and Nutrition: Nearby grass stands. The muscles of California harvester ants “burn lipids for energy instead of the carbohydrates typically burned by most other animals (Taber, 69; see Martin and Lieb, 1979). The presence of chitinase (an enzyme) “allows them to break down the exoskeletons of the other insects they feed upon (Taber, 69 citing MacKay, 1981). California harvesters “removed more >2,000 μm particle mass but visited dishes containing 1,000 to 2,000 μm particles more often, according to Linda M. Hooper-bùi, Arthur G. Appel, and Michael K. Rust (2002) .
Nest structure: Upwards of 3,000 members. Located in “dry sandy soil…low flat crater” (Hogue, 329); “bowl-shaped crater instead of a dome-shaped mound. The crater is up to 2 feet wide and 2 inches deep. The entrance is in the middle or just off-center, and visible at some distance is the ring of chaff (discarded hulls of seeds), which looks like a golden halo about the whole edifice. Sometimes the nest superstructure is a mound up to 12 feet wide instead of a crater, or it is little more than a hole in the ground (Taber, 22). Nest entrance may be moved from time to time (Taber, 56) and orientation is SE to sun. Closed in the evening and reopened in morning; closed in late fall for overwintering.
Habitat Range: California, Nevada, Arizona, New Mexico, Texas; and possibly Oklahoma panhandle; northern Baja as well as the Mexican states of Sonora and Chihuahua.
Behavior: Navigation by sight and polarized light as well as chemical trails; raise rear-end, presumably due to heat of soil (Taber, 41 citing Wheeler 1902). Occasional group foraging (Taber, 40 citing Whitford, 1976).
Interest/Importance: Communication by drumming and stridulation (i.e., one body part against another). When California Harvester ants “move they take their garbage as well” (Taber, 26). Horned toads prey on harvester ants (Hogue, 329). California harvester ants can withstand 156,000 roentgens (Taber, 71); hence, they, along with cockroaches, will inherit the earth after a nuclear holocaust. Most important animal in the desert, according to James W. Cornett (9 November 2008).
Taxonomic History: Wheeler, W.M. 1902c: 387 (w.) U.S.A. Cole, 1968: 67 (q.m.); Taber, Cokendolpher & Francke, 1988: 51 (k.). Senior synonym of ferrugineus: Cole, 1968: 65.
1) Charles L. Hogue, Insects of the Los Angeles Basin (Los Angeles: NHM of LA, 1993).
2) Stephen W. Taber, The World of the Harvester Ants, Natural History Series, No. 23 (College Station: Texas A&M University, 1998.
3) Linda M. Hooper-bùi, Arthur G. Appel, and Michael K. Rust, “Preference of Food Particle Size Among Several Urban Ant Species,” Journal of Economic Entomology 95 (2002): 1222–1228.
4) Wendy Marussich, “Testing Myrmecochory from the Ant's Perspective: The Effects of Datura wrightii and D. discolor on Queen Survival and Brood Production in Pogonomyrmex californicus,” Insectes Sociaux, 53 (No. 4, December 2006): 403-411.