W. auropunctata workers are monomorphic, which means they display no physical differentiation (Holway et al., 2002). The ants are typically small to medium-sized, with the workers ranging from 1-2 mm (Holway et al., 2002;Longino and Fernández, 2007). The little fire ant is light to golden brown in colour. The gaster (abdomen) is often darker. The pedicel, between the thorax and gaster, has two segments;the petiole and postpetiole. The petiole is 'hatchet-like', with a node that is almost rectangular in profile and higher than the postpetiole. The antenna has 11 segments, with the last two segments greatly enlarged into a distinct club. The antennal scape (the first segment) is received into a distinct groove (scrobe) that extends almost to the posterior border of the head. The propodeum has long and sharp epinotal spines (propodeal spines). The body is sparsely covered with long, erect hairs. This species is well-known for a painful sting, seemingly out of proportion to its size.
Ants can be detected by conducting surveillance programmes in high risk sites with favourable ant habitats. Surveillance should not occur during or after rain when the ground surface is still wet. Inspection is unsuitable in excessively windy days when ant activity is minimal.
The following is adopted from Vanderwoude et al. (2009):
Three survey methods can be used to detect W. auropunctata: vial baiting, chop stick baiting and visual surveys.
Vial Baiting
Vial baiting with an attractant is systematic and most suitable for surveys of industrial sites and nurseries. Little fire ant vial baits contain peanut butter which can be made by smearing a line of peanut butter (half the size of a pea) on the inner side of each bait vial (60 cc plastic containers with lids). Baits should be freshly made as ants are are not as interested in old and dried-up baits. The survey is carried out by placing bait vials in a grid pattern, with a minimum of one bait container per 10 x 10 m grid. Bait containers should be placed in suitable ant habitats and should be collected within 60-90 minutes after placement in the field.
Chop Stick Bating
Chop stick baiting is useful when targeting habitat trees as well as individual potted plants. One end of the chopstick needs to be painted (both sides) so that these can be easily relocated in the field. Morning or overcast days are the best times to bait. If surveying at midday on hot, low humidity days, baits should be placed in shady spots.
Dip the unpainted end of a chopstick in peanut butter to get a light coating extending about halfway up the stick. Place the chopsticks with peanut butter on the ground every 5-10 m. Only place in suitable habitats such as bases of trees/shrubs and in shady spots. Leave chopsticks with peanut butter for at least 45 minutes, not more than 2 hours before collecting. While collecting check for presence/absence of W. auropunctata.
Visual Survey
Visual surveys are appropriate when targeting discrete locations within a large site or for covering large areas quickly. It is very efficient in high density areas. Causton et al. (2005) used hot-dogs (ca 5 mm thick, made of beef) on the lower ends of 30 cm wire flags that were placed on the ground at 5 m intervals along a transect to detect W. auropunctata. These baits were checked after 45 minutes.
Related invasive species
- Wasmannia auropunctata
Related Farm Practice
- Light
Wasmannia auropunctata (the little fire ant) is responsible for reducing species diversity, reducing overall abundance of flying and tree-dwelling insects, and eliminating arachnid populations. It is also known for its painful stings. On the Galapagos, it eats the hatchlings of tortoises and attacks the eyes and cloacae of the adult tortoises. It is considered to be perhaps the greatest ant species threat in the Pacific region. This species has been nominated among 100 of the 'World's Worst' invaders.