The Ants That Attend the Extrafloral Nectaries of Acacia ulicifolia

Acacia ulicifolia, commonly known as prickly Moses, is a small Australian wattle with sharp, narrow phyllodes and pale yellow flower clusters. On the Tomaree Peninsula it belongs to the coastal heath and dry bushland flora, where plants cope with sandy soils, salt-laden winds, intense sunlight and periodic fire. Its flowers attract familiar pollinators, yet another partnership takes place away from the blooms.

Tiny glands on the plant’s vegetative parts can produce sugar-rich liquid called extrafloral nectar. Ants visit these glands to feed, and their regular movement across the plant may discourage some herbivorous insects. The relationship is easy to miss because the ants may be only a few millimetres long, while the nectar glands are far less conspicuous than the yellow flowers.

The Plant And Its Nectar Glands

Unlike floral nectar, extrafloral nectar does not primarily reward pollinators. It is produced by a plant structure outside the flower, often on or near a leaf, phyllode or stem. In Acacia species, these glands form part of a defensive arrangement: the plant provides food, while visiting insects may patrol the surfaces where caterpillars, beetles and sap-feeding insects might arrive.

Acacia ulicifolia’s phyllodes are adapted to exposed Australian conditions. They reduce the plant’s dependence on broad, delicate leaves and give the shrub a distinctive prickly outline. Nectar production can vary with plant condition, temperature, rainfall and the presence of herbivores, so an apparently inactive shrub may become attractive to ants after rain or during a new flush of growth.

The exact appearance of a gland is best studied with a hand lens and a clear photograph. A glossy spot, a shallow depression or a small raised structure may be mistaken for damage or dust. Photographs in the Tomaree Peninsula flora collection help place this fine-scale feature within the wider setting of local heath, woodland and coastal vegetation.

Which Ants May Be Present

There is no single ant species that attends every Acacia ulicifolia plant. The visitors depend on season, colony location, soil moisture, nearby vegetation and the plant’s accessibility. Small black, brown or reddish ants may arrive in files, while larger solitary workers may inspect the phyllodes at intervals. Colour alone is not reliable for identification.

Australian bushland commonly supports genera such as Iridomyrmex, Polyrhachis, Crematogaster and Anonychomyrma, but a confident record requires details of body shape, hair, node structure, mandibles and behaviour. A close photograph, location, date and a note about the ants’ route are more useful than a common-name guess. The nest may be under leaf litter, beneath a stone, inside loose soil or some distance from the shrub.

Ant activity also changes through the day. Warm morning weather can bring workers onto sunlit foliage, while very hot conditions may push them into shade. After rain, ants may follow new trails to fresh nectar sources. In a home garden near Nelson Bay, the same Acacia can therefore appear ant-free during a brief visit and busy a few hours later.

Why The Ants Keep Returning

Extrafloral nectar contains water and carbohydrates, making it a convenient energy source for worker ants. A colony can use this liquid to supplement prey, honeydew from sap-feeding insects and food gathered from the ground. In return, the ants’ constant movement may make a plant less attractive to some insects searching for a feeding or egg-laying site.

This defence is usually described as mutualism, but the benefits are not perfectly equal or fixed. Ants may protect one plant during a particular period, then move elsewhere when a stronger food source appears. Some ants may also farm scale insects or aphids for honeydew, creating an association that benefits the ants but can place additional stress on the plant.

The value of ant attendance is therefore best understood as a changing ecological exchange. It is not a guarantee that Acacia ulicifolia will remain free of chewing insects. Rather, the ants add one layer to the shrub’s existing defences, alongside tough phyllodes, chemical compounds, growth form and the activity of other predators.

Protection Has Limits

Ants can deter caterpillars and other soft-bodied herbivores by biting, chasing or simply making the plant difficult to occupy. Their presence may also affect which insects choose to settle nearby. In some ecosystems, plants with active nectar glands experience less damage than similar plants whose glands are blocked or inactive.

The outcome depends on the ant’s temperament and the herbivore involved. A small nectar-feeding ant may have little effect on a large beetle, while a more aggressive colony can dominate a branch. Rain can dilute nectar, wind can interrupt trails and competing flowers or honeydew can draw workers away. The plant receives protection only while the visitors are present and motivated.

Gardeners sometimes interpret every ant trail as evidence of a healthy partnership. That is too simple. A sudden increase in ants may signal nectar production, but it can also indicate scale insects, aphids or another food source. Looking at both the ants and the plant’s condition prevents a useful ecological observation from becoming an assumption.

A Coastal Heathland Relationship

On the Tomaree Peninsula, Acacia ulicifolia grows within a mosaic shaped by wind exposure, sandy ground, drainage and fire history. A shrub beside an open track may support a different ant community from one sheltered among banksias, tea-trees and grasses. The surrounding ground cover matters because ants travel through litter, roots, fallen timber and shallow soil before climbing the phyllodes.

This is one reason a plant photograph should include habitat details when possible. A close image records the gland and ants, while a wider frame shows whether the shrub stands in heath, woodland edge, wet depression or disturbed roadside vegetation. Nearby flowering species, including coast tea-tree, alter the seasonal supply of nectar and pollen; the seasonal tea-tree display provides a useful comparison for observing how local flowering changes insect activity.

Nelson Bay’s bushwalkers often notice flowering shrubs while walking familiar tracks, but the ant layer rewards a slower pace. A few minutes beside one plant can reveal trails crossing several phyllodes, workers pausing at particular points and sudden changes when a shadow moves across the foliage.

Observing Ants Without Disturbance

A hand lens, phone camera and notebook are enough for a basic record. Note the date, weather, time, plant size, habitat and approximate number of ants. Photograph the whole shrub first, then a branch and finally the smallest practical close-up. Avoid touching the nectar glands, spraying the plant or placing bait beside it, because these actions change the behaviour being studied.

Observation is particularly valuable in a garden containing local native species. Choosing plants suited to the sandy soils and rainfall patterns of Port Stephens reduces the need for heavy watering and creates habitat continuity for insects. Guidance on designing a local native garden can help connect an Acacia shrub with other regionally appropriate plants rather than treating it as an isolated ornamental specimen.

Australian gardeners should also resist collecting ants, soil or plant material from bushland for a backyard experiment. In NSW national parks and reserves, removing natural material generally requires authorisation under the National Parks and Wildlife Act 1974. A photograph and written observation preserve useful information without disturbing a colony or damaging a native shrub.

What The Partnership Reveals

The ants attending Acacia ulicifolia demonstrate that plant ecology operates at several scales. At a distance, the shrub is a recognisable component of Tomaree heath. Close up, its phyllodes contain small nectar-producing structures, and closer still, an ant trail links the plant to a colony hidden in the ground. Each scale explains part of the same relationship.

The observation also connects backyard habits with local conservation. People in Newcastle, Sydney and regional NSW increasingly grow native plants for lower water use, wildlife value and a sense of place, while local nurseries and community markets promote species suitable for nearby conditions. Buying nursery-propagated plants instead of taking specimens from reserves supports legal cultivation and protects wild populations.

Even a textile or illustration can carry this ecological detail into everyday life. Botanical imagery such as that found through Australian fabric designs can celebrate plant form, while field photographs add the less obvious story of ants, nectar and defence. Acacia ulicifolia is therefore more than a prickly wattle with attractive flowers: it is a living meeting point between shrub, insect colony, soil and coastal landscape.