Ants have body language. This body language can vary by species and by caste, but there are some general rules that I've noticed.
mandibles open: want to bite, I can bite!
antennae upright moving in air: what do my sisters think?
antennae folded: resting or sleeping
antennae tapping another ant's body: hi, who the heck are you?
antennae tapping another ant's head: I'm hungry feed me
In general whatever the antennae are touching has the ants attention, they are far more sensitive than the ants eyes in most species. Many ants have poor vision or only the ability to sense light and shadow.
legs stiff, standing tall: I'm very big and intimidating
legs tucked, body low: no ant here! move along... or resting
varies by species:
gaster(ant butt) raised: I could spray you with acid! OR
gaster tucked under body: I could spray you with acid!
tapping gaster on the ground in a quick jerk: This makes a noise other ants can hear, and it means "danger" or "get ready to attack" majors of camponotus often do this.
dragging gaster while walking: something good is on this trail! follow!
dragging gaster in a circle around an enemy "here's the jerk! get 'em girls!"
running in circles mandibles open: I'm sounding the alarm! Calling my sisters!
some camponotus species:
front legs up like boxing gloves, back four legs tall: I'm ready to box with another ant to determine who is allowed here.
Not all ants have boxing to determine territory, some will just grapple or even fight to the death.
Body language isn't as important as pheromones for ants, but smells are harder us us to learn as we can't really decode them easily with our noses.
What ant body language have you noticed?