To keep this close to Japanese: I didn't know the kanji for 蟻(あり) , but look at the components! 虫 and 義 – how very fitting, isn't it?
義 is also a productive phonetic component, so you can fairly confidently guess that 蟻's 音読み is ギ :)
PS: We have a wide variety of ant species where I live (Bulgaria), including multiple Camponotus species. Though I've never stopped to measure any of them :D
The "tiny red ones that bite awfully hard" could be a species of Myrmica?
@GroovyMAXIMUM , thank you! Now I feel better about my bad habit of taking forever to finish my coffee. I'll reframe it as "feeding ants their supplements". Well, it's probably still best if they don't fall in that mug.
The bitey ones are tiny, under 2 mm I'd say by eye. Sometimes so small you can't tell what kind of insects they are without looking at them from up close – then you see the trademark ant body shape. Some are brick red, some yellowish orange (not sure if different species or just seen in different sunlight, or semitransparent because so tiny). Have I mentioned they bite really hard? :)
The book with the ant computer is Adrian Tchaikovsky's Children of Time trilogy. Amazing if you like SF (even if you don't), and tackling serious themes like what makes us human, what makes a creature a person, how we perceive "otherness" and so on. Warning: not for the arachnofobic.
@ギョルギ九十三 whose name I never seem to manage to quote (@) effectively, thanks to your comment I've now learned 蟻走感 and 蟻酸! Also, hello, neighbour, for part of the year I live just north of you.
Speaking of spiders, this one is definitely NOT a pet, but it decided our home was its home. It took two people and a lot of strategising to catch and release it, hunters are amazingly smart. For scale, the diameter of that glass is 8 cm.