The latest research into ant behaviour shows that ant larvae have a pivotal role in allowing adult ants to ingest solid food.
When discussing ant bait performance, there is the general perception that liquid ant baits are better. This is based on the understanding that worker ants can only eat liquid bait and so it is easy for them to ingest liquid or gel baits in the field and transport them back to the nest. However, although workers generally prefer high carbohydrate foods for their individual requirements – they don’t require protein for growth, only sugar for energy – they will select non-sugar foods depending on the requirements of the colony. Indeed, all ant species take at least some solid food back to the nest, as protein is required for larval development and growth, and protein is often only available as a solid material. So how does the ant colony process solid food?
The mouthparts of adult ants do not allow them to chew and ingest solid food. Indeed, their infrabuccal plate actually filters out solid particles as they imbibe liquid. Of course, their mandibles allow them to cut up and transport solid food, so they can easily take such food back to the nest. These solid food particles, which are often high in protein, are required by the larvae for growth and by the queen for egg laying. It is the larvae that are key in processing the solid foods for the colony.
Previously it was thought that ant larvae would chew and ingest solid food and then regurgitate the juices for consumption by workers and for distribution to the queen and rest of the colony. However, it has recently been established, at least in some species, that the food is placed on the belly surfaces of the larvae, generally the older larvae, for digestion externally. In both red imported fire ants (Solenopsis invicta) and big-headed or coastal brown ants (Pheidole megacephala), the older larvae lay on their backs and workers place the solid food in a special groove on the belly of the larvae (circled in red, main picture above). The larvae spit out digestive enzymes onto the food and a few hours later the workers return to imbibe the resulting liquid meal. This liquified protein is then fed back to the larvae that did all the work and is also passed on to other larvae and reproductives.
In many ways, Synergy Pro and Distance Plus, the granule-based baits from Sumitomo Chemical are in fact the ideal bait format, especially for outdoor ants. Although these granular baits look dry, they actually contain oil, which provides the initial attraction to workers and a food source for them to imbibe. However, they also provide them with the solid protein food to take back to the colony. This solid food, which is then digested by the larvae, becomes a preferred food source to be fed to the other larvae and reproductives. This ensures that the bait toxicant is delivered to the life-stages critical for colony survival and is why Synergy Pro and Distance Plus are particularly useful in eliminating large outdoor ant infestations.
Distance Plus is a corn grit-based bait containing only the IGR pyriproxfen. The oil- and plant-based protein formulation targets primarily oil and seed feeders such as big-headed ants, green-head ants (Rhytidoponera metallica) and fire ants. Although the IGR-based formulation means that colony elimination may take several weeks, its unscheduled poison classification means it’s a great option for sensitive accounts.
In contrast, Synergy Pro contains both plant and animal proteins, as well as oil and carbohydrate components, and so appeals to a broader range of ant species. It also contains hydramethylnon as well as pyriproxyfen, delivering faster colony control, typically in 1-2 weeks.