In this article, I’m going to brief on how do ants sense food.
Sugar has a slight odor, specifically granulated beet sugar. While all species of ants can differentiate between a wide variety of odors, the smelling range differs from a few centimeters to meters. Desert ants are able to smell sugar in a distance of up to 3 meters.
the food sources that ants cannot smell from a distance they ‘smell’ it (contact chemoreception) by touching it. So in a way, all the food they detect, they detect it by smelling. So yes off course, ants smell (although contact chemoreception is more like taste) the sugar.
The ant colonies send scout ants to search for food in various directions, often up to a range of 100 to 200 meters. (Depends on the territorial boundary and time of the year). The scout marches steadily in less circuitous paths initially if it has memories of previous feeder locations. (Ants use visual landmarks, and a stereo-smell system to create an odor map and navigate) Periodically it will halt and look for olfactory cues. It will then take into a more circuitous random search. And as it nears the sugar and can smell it, its search ends.
The antennae of ants have hair-like sensilla that contain one or more sensory neurons. Most of the sensilla contain olfactory neurons. Each neuron sends a long nerve fiber through the antennal nerve that terminate in the antennal lobe of its brain. The axons from the olfactory neurons terminate in the lobe in globular structures called glomeruli. The antennal lobe of ants is particularly large and it has around 420-430 glomeruli. (A honey bee has 160). The more the glomeruli, the more variety of odors the ant can process. This provides for the acute smell sense of ants.
Once food is found, the scout collects a little sample of it and marches back to the colony finding the shortest route and leaving a pheromone trail behind. Once in the colony the other ants analyze the food the scout brought and take the trail set by the scout. As more ants get on the trail, they make the marking stronger so that other ants who went out on searches can smell the trail and join them.
This sugar detection process is not entirely intuitive and needs to be learnt. A leader scout takes a willing pupil with it to teach how to search for food. The pupil walks behind the teacher in a paired march called tandem running. The pair stops from time to time so that the pupil can commit the landmarks to its memory. When the pupil is done, it taps on its master’s hind legs or abdomen two times and they start moving again. (If you see a pair stop like that, you can tap the hind legs of the master ant with a hair and it will keep moving. If the distance between the pupil and the master gets too large the master slows down while the pupil runs to catch up). They have a set of simple eyes with many unit called ommatidia that they use to detect light, they use their two antenna to detect obstacles or enemies, and in recognition of their mates and nest.

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