Searching for ants at Port of Napier.
Image – Travis Ashcroft

Direct Searching

Also known as visual surveying or hand collecting. Direct searching involves searching for, and collecting, ants in different microhabitats within an area. Direct sampling is particularly useful when the main objective is to determine which ant species are present or absent, and no information is required on their abundance or biology. Direct searching is highly suitable for detecting the presence or absence of invasive ant species.

Direct searching is an easily learned technique. It basically requires good observation skills and careful examination of different microhabitats where ants are commonly found. Although the targeted ants are quite small (1–4 mm), they are diurnal and usually quite active on the ground.

When ants are discovered, an aspirator is the best method to collect them. The aspirator (also known as a 'pooter') is used to 'suck' ants into a tube, where they can then be transferred to a vial. Approximately five ant specimens should be collected if possible – having several specimens may help during identification.

Direct searching does not have a defined ‘sampling unit’ or ‘sampling area’, so to standardise sampling effort it is recommended that the time spent searching for ants at each site is recorded. Approximately 30 minutes should be spent at each site, although this may vary depending on the size of the site, etc. However, a minimum of 15 minutes must be spent at each site. At the end of the 30-minute period all ants collected are placed into one vial of ethanol.

The advantages of direct searching are:

• Baiting is an easily learned technique
• Less time is needed in the laboratory to sort and identify ant species because there is no need to extract ants from messy baits, or from the litter or soil. The amount of time spent in the surveillance of sites is therefore maximised
• One visit is often sufficient (but see Detection)
• A large number of sites can be visited in a single day
• Minimal equipment/expense is required
• More flexibility when at an area, to ‘wander’
• Rapid identification of infestation limits
• No data gaps (no lost vials or false negatives)
• Ideal for locating residual nests for follow-up treatment
• No non-target catch

The disadvantages of direct searching are:

• Argentine ant field identification skills are useful (although all ants can be brought back to the laboratory and identified, so this is not an absolute requirement)
• Nest disturbance could scatter queens
• Large infestations require more than one person or more than one day to survey (although for surveillance and determining their ‘initial presence’ this is not an issue)
• Public interest can result in some delays. However, this can also be an opportunity to query members of the public about ‘pest ants in their area’ and encourage them to be ‘on the lookout’.