Aphaenogaster occidentalis
Temperature
22–27 °C
Humidity
50–70%
Colony size
500–3,000
Queen size
8–10 mm
Worker size
5–7 mm
Hibernation temp
10 °C
Diet
Care Guide
Aphaenogaster occidentalis is the western counterpart to the eastern North American Aphaenogaster species, ranging across dry oak and pine woodlands of the Rocky Mountain and intermountain west. The queen reaches 8–10 mm, and workers measure 5–7 mm. Coloration is darker than its eastern cousins, often a bronzy-brown rather than orange, with the same elegant long-legged build typical of the genus.
This species is well adapted to the relatively dry, warm conditions of western forests, tolerating temperatures up to around 27 °C without stress. Colonies remain modest in size, typically 500 to 3,000 workers, and behave as classic generalists — foraging for small invertebrates, scavenging, collecting sugary fluids, and dispersing seeds with elaiosomes.
Like all members of the genus, A. occidentalis founds new colonies semi-claustrally. The queen forages during the founding stage and cannot be sealed away with only her brood; she must be offered food from the start.
Care difficulty
Intermediate. The species is more heat-tolerant than its eastern relatives but still requires a proper winter hibernation period at around 10 °C, and semi-claustral founding adds a small layer of complexity for new keepers.
Housing
A small starter setup with a moist nesting chamber and a drier outworld suits this species well. Keep temperatures at 22–27 °C during the active season with humidity at 50–70 %. Offer a varied diet of fruit flies, small crickets, sugar water, and occasional seeds with elaiosomes. Hibernate at 10 °C for at least two months from late autumn through early spring.
First days after purchase
Allow the colony or founding queen to settle in a quiet, dimly lit location. Offer a freshly killed fruit fly and a tiny droplet of sugar water during the first day, and check on water availability without disturbing the brood. Once the colony reaches 25 to 30 workers, transition to a small formicarium with proper foraging space.