*Also includes Formica rubicunda, subintegra, wheelerii, and other Formica sanguinea group species
Formica aserva is one of my favourite native species. They're found across Canada, and can be frequently found in raiding columns stretching hundreds of meters. As you watch the ants march by, you notice they're all carrying pupae, larvae, and other brood. Most people think "Oh they're moving to a new place" but often this could not be farther from the truth. If you follow them back to home base, you'll see a mix of red ants and black ants. Make no mistake, those black ants are slaves.
Formica aserva is dulotic, meaning it is a slave raider. These ants scout out the nests of Formica subsericea, F. podzolica, and other related species, before charging in to steal the brood which the resident colony is unable to evacuate.
Populations of this species differ across Canada in their behaviour. In places with lots of host colonies, they will often require slaves and have colonies of over 90% slave workers. In more isolated areas, they can even become non-parasitic altogether. However, having access to slaves is almost universally better than not.
Deception is an integral part of this species's strategy, and the host Formica ants will revolt and eat the brood if they find out they're in the nest of the invader. The first biological workers will likely be dark, and mainly care for the brood. This seems to calm the hosts down as well.
Formica aserva are a large parasitic variety of Formica which live in throughout Canada. They're have red head and thoraxes, with shint black abdomens. These are larger than most Formica with queens from 8-10 mm and workers from 6-10 mm. They grow large colonies up to 15,000 workers in just 3 years. They prefer 22-26 Celsius and like around 50% humidity, though there is slight variation across species. They're more skittish than most ants, and so are of medium difficulty to start, but are extremely enthusiastic and fast growing once they break 50 workers. In the wild, Formica are some of the most dominant ants, hunting down other species and consuming large amounts of biomass. We get many of these each year, though the numbers are variable. Note that this species requires good ventilation, or their formic acid spray may become an issue.
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