By: Gerry Wegner Ph.D.
P. pubens workers are monomorphic and are about 1/8-inch (2.6-to 3-millimeters) long. They range in color from golden brown to reddish-brown. (Note: P. longicornis is bluish-gray to black; P. bourbonica is completely dark brown or black; and P. guatamalensis is yellowish-brown to dark brown with light-colored middle and hind coxae.) The antennae are 12-segmented and are not clubbed. To the naked eye, this ant’s body appears smooth and glossy; however, under magnification, numerous dense hairs (setae) are apparent. Another ant species that bears resemblance to the Caribbean crazy ant is the small (false) honey ant (Prenolepis imparis), except that workers of the latter species have an hour-glass shaped alitrunk (prothoracic plus mesothoracic portions of the mesosoma) when viewed from above, and do not move nearly as fast as the former species.
The Caribbean crazy ant is both an introduced species and an emerging pest species. It was described from the Lesser Antilles of the West Indian islands in the 1890s and was first noticed in Coral Gables and Miami, Fla., in 1953. Since then, it has been encountered in coastal cities mainly in the southern half of Florida although its movement inward and northward is inevitable, as evidenced by reports from Jacksonville, Fla., and possibly Houston. Texans are investigating whether they have the same species or a slightly different ant, which they have designated Paratrechinaspecies near pubens, the “rasberry crazy ant.”
The prominent foraging trails of P. pubens, both outdoors and indoors, make it obvious to the general public and enhance its status as a nuisance pest. PMPs have become all too aware of this species as a result of calls by alarmed and annoyed myrmecophobic customers. To date, only short-lived results have been obtained by PMPs accustomed to using a shot-gun approach involving residual liquid and granular pyrethroid insecticide barrier applications. Although worker ants will accept certain brands of sweet liquid and gel baits, recruitment and sustained bait acceptance have not been observed. University of Florida entomologists are working with Florida PMPs to develop a protocol that delivers acceptable long-term control of this species.
BIOLOGY
Despite the fact that P. pubens has been in Florida for half a century, very little is known of its biology. Nests have been discovered in the soil beneath logs, railroad ties, wooden debris and pavement, as well as in building soffits, exterior walls and electric boxes/outlets. Based on observations, P. pubens workers tend homopteran honeydew producers and use dead insects as a source of protein and fat to feed their larvae. This species is considered to be polygamous (having multiple queens per colony), polydomous (nesting in multiple locations) and seems to have an activity threshold around 60°F (16°C). Polydomous colonies may be comprised of several hundred thousand individuals. Some entomologists have observed workers of P. pubens competing with workers of the red imported fire ant, Solenopsis invicta.
IPM MEASURES
Begin with positive identification of specimens to species. Acceptable levels of control may or may not be obtained as a result of implementing measures being recommended for the tramp ant species.
- Vegetation, mulch and other shelter-providing landscaping features should be kept to a minimum around structures.
- Debris piles should be removed.
- Consider strategically targeted applications of non-repellent residual liquid insecticides when allowed by product labeling directions where ants are trailing and suspected of nesting.
- Offer foraging Caribbean crazy ant workers several brands of sweet liquid and gel ant baits to determine which products prove acceptable and elicit recruitment.
- Share with customers your recommendations for food-and-beverage clean-up and storage.
Wegner is the technical director and staff entomologist of Varment Guard Environmental Services in Columbus, Ohio. You can reach him at 614-794-8169 or e-mail gerry.wegner@varmentguard.com.
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