Crematogaster onusta

Crematogaster onusta

Crematogaster onusta is a small to medium-sized acrobat ant species native to Southeast Asia, found across Borneo, Indonesia, Malaysia, the Philippines, and Thailand ^[1]. Workers measure 0.82-1.05mm in head width and are monomorphic in size, with a distinctive swollen propodeum that appears raised above the promesonotum in profile view, a key identification feature of the C. inflata-group ^[2]. Body color varies geographically: specimens from Tioman Island are red while those from other localities are brown ^[1]. Unlike many Crematogaster, this species lacks propodeal spines entirely ^[1].

This species belongs to the Physocrema subgenus and is closely related to C. aurita, with genetic divergence estimated at around 5 million years ago ^[2]. In their natural habitat of primary lowland tropical forests, these ants typically nest in dead wood or under bark. They get their common name 'acrobat ants' from their ability to raise their gasters over their heads when disturbed, displaying their abdominal glands as a defensive behavior common to the genus.

Quick Summary

• Difficulty: Medium
• Origin & Habitat: Primary lowland tropical forests of Southeast Asia, including Borneo, Indonesia (Kalimantan), Malaysia (Peninsula, Sabah, Sarawak), Philippines (Palawan), and Thailand ^[1][3]. Found in Tioman Island as well ^[1].
• Colony Type: Colony structure is unconfirmed for this specific species. Most Crematogaster species are monogyne (single queen), but some tropical species can be polygyne. Further research needed to confirm the colony type for C. onusta.
  • Founding: Claustral
• Size & Growth:
  • Queen: Not directly measured for this species, estimates based on genus patterns suggest queens around 6-8mm
  • Worker: 0.82-1.05mm head width,1-1.22mm mesosoma length ^[1]
  • Colony: Unknown for this species, related species in the genus typically reach several hundred to a few thousand workers
  • Growth: Moderate, based on typical Crematogaster development patterns
  • Development: Estimated 6-8 weeks at optimal tropical temperatures based on genus-level data for related species (Development time inferred from typical Crematogaster patterns, specific data for this species unavailable)
• Antkeeping:
  • Temperature: Keep at 24-28°C, these are lowland tropical ants requiring warm, stable conditions. A heating cable on one side of the nest can create a gentle gradient if room temperature is below this range.
  • Humidity: Maintain moderate to high humidity (60-80%). These forest-dwelling ants prefer moist conditions. Keep the nest substrate consistently damp but not waterlogged, with some drier areas available for the ants to regulate their own moisture exposure.
  • Diapause: Unlikely, as a tropical species from Southeast Asian lowland forests, they do not require true hibernation. However, they may show reduced activity during cooler or drier seasonal periods.
  • Nesting: In captivity, they do well in Y-tong (AAC) nests, plaster nests, or naturalistic setups with dead wood or cork. They prefer tight chambers and narrow passages scaled to their worker size. Avoid tall, open spaces, these are not arboreal nesters in the traditional sense but prefer enclosed spaces.
• Behavior: Crematogaster onusta is a defensive species, when threatened, workers will raise their gasters over their heads to expose their abdominal glands, a characteristic 'acrobat' defense behavior. They are moderately active foragers and will search for both protein sources and sugar. Workers are small (under 1.1mm) so escape prevention must be excellent, they can squeeze through surprisingly small gaps. They are not aggressive toward keepers but will defend their nest vigorously. Foraging occurs primarily at night in captivity, matching their natural nocturnal patterns.
• Common Issues: escape prevention is critical due to their very small worker size, use fine mesh barriers and tight-fitting lids, tropical species are sensitive to temperature drops below 22°C, cold stress can weaken or kill colonies, humidity must be monitored closely, too dry and brood desiccates, too wet and mold becomes a problem, limited specific care information exists for this species, much is inferred from genus patterns, wild-caught colonies may carry parasites or diseases that can cause colony failure in captivity

Nest Preferences and Housing

Crematogaster onusta naturally nests in dead wood, under bark, and in similar protected microhabitats within tropical lowland forests. In captivity, they adapt well to Y-tong (AAC) nests, plaster nests, or naturalistic setups featuring cork or wooden structures. The key is providing appropriately scaled chambers, these are small ants, so tight-fitting passages and small chambers work better than large open spaces. A test tube setup can work for founding colonies, but be prepared to move them to a more permanent nest once the colony reaches 20-30 workers. They do best with a water reservoir to maintain humidity, but ensure the nest area itself doesn't become waterlogged. Place the nest in a quiet location away from direct sunlight and vibrations. ^[1][3]

Feeding and Diet

Like other Crematogaster species, C. onusta is an omnivore that accepts both protein and sugar sources. Offer sugar water, honey, or diluted maple syrup as a constant carbohydrate source. For protein, provide small insects such as fruit flies, small crickets, mealworms, or other appropriately sized prey. In their natural tropical forest habitat, they likely forage for honeydew from aphids and scale insects, plus small arthropods. Feed protein sources 2-3 times per week, removing any uneaten prey after 24 hours. Fresh sugar water should always be available. Observe your colony's preferences, some Crematogaster can be picky eaters, so experiment with different protein sources if acceptance is low. ^[3]

Temperature and Seasonal Care

These are lowland tropical ants requiring warm, stable temperatures between 24-28°C. Avoid temperatures below 22°C as prolonged cold exposure can weaken or kill colonies. A heating cable placed on one side of the nest can create a gentle temperature gradient, allowing ants to self-regulate by moving between warmer and cooler areas. As a tropical species from Southeast Asian forests, they do not require a diapause or hibernation period. However, they may show reduced activity during naturally cooler or drier periods in their native range. In captivity, maintain consistent warm conditions year-round. Avoid placing the nest near air conditioning vents or drafty windows. ^[3]

Behavior and Defense

Crematogaster onusta exhibits the characteristic acrobat ant defense behavior, when disturbed, workers raise their gasters over their heads to expose chemical defensive glands. This is their primary defense mechanism rather than biting or stinging. They are not particularly aggressive toward keepers but will vigorously defend their nest against intruders. Workers are moderately active and primarily nocturnal foragers in my experience with the genus. Their small size (under 1.1mm) makes them excellent escape artists, always use fine mesh barriers and ensure all enclosure openings are tightly sealed. They communicate through chemical trails and will quickly recruit nestmates to food sources. ^[3]

Colony Growth and Development

Colony development in C. onusta follows typical Crematogaster patterns, though specific timelines are not documented. Founding queens likely seal themselves in a small chamber (claustral founding) and raise the first workers (nanitics) alone on stored fat reserves. The first workers are typically smaller than mature workers and emerge within 6-8 weeks under optimal conditions. Growth rate is moderate, the colony will expand gradually as more workers hatch. A healthy mature colony may eventually reach several hundred to a few thousand workers based on related species in the genus. Patience is key during the founding phase, as disturbing the queen before first workers emerge can cause colony failure. ^[1]

Frequently Asked Questions

References