Crematogaster indosinensis

Quick Summary

• Difficulty: Unknown
• Origin & Habitat: Known only from Kampong Thom Province, Cambodia (12°34′N,105°23′E) in natural forest ^[1]. Collected from permanent sample plots established by the Cambodian Forestry Administration ^[2].
• Colony Type: Unconfirmed, colony structure has not been documented for this species.
• Size & Growth:
  • Queen: Size data unavailable, queen caste has not been described ^[1]
  • Worker: Size data unavailable, only head measurements exist in the literature. Based on Crematogaster genus patterns, workers likely measure approximately 2-4 mm in total length.
  • Colony: Unknown, only 4 worker specimens have been collected ^[1]
  • Growth: Unknown
  • Development: Unconfirmed, no development data exists for this species. (This is a newly described species with essentially no biological data.)
• Antkeeping:
  • Temperature: Unknown, no thermal studies exist. Based on its Cambodian origin (tropical Southeast Asia), keep warm in the low-to-mid 20s°C range. Monitor colony activity and adjust based on behavior.
  • Humidity: Unknown, no humidity data exists. As a forest-dwelling species from Cambodia, moderate to high humidity is likely appropriate. Keep the nest substrate consistently moist but not waterlogged.
  • Diapause: Unknown, no seasonal data exists. As a tropical species from Cambodia, diapause may not be required, but this is unconfirmed.
  • Nesting: Unknown, no nesting observations exist. Most Crematogaster species nest in rotting wood, under bark, or in plant cavities. A Y-tong (AAC) nest or plaster nest with some moisture retention would be a reasonable starting point.
• Behavior: Workers were collected foraging on lower vegetation, suggesting they are active foragers. Crematogaster ants are known for their characteristic heart-shaped gaster (abdomen) which they raise as a defensive posture when threatened. They have a smear-type stinger used to wipe venom onto enemies rather than piercing flesh. Escape risk is moderate due to their small size, use standard barrier methods. Temperament is not documented but most Crematogaster are moderately aggressive when defending the colony ^[1].
• Common Issues: this is a newly described species with essentially no captive care data, expect a learning curve, queen and colony structure unconfirmed, you may get surprises when establishing colonies, no information on what foods they accept, be prepared to experiment, wild-caught colonies may have parasites or diseases since no captive breeding exists, temperature and humidity requirements are estimates, monitor your colony closely

Species Discovery and Taxonomy

Crematogaster indosinensis was described in 2016 by Hosoishi and Ogata, making it one of the newest ant species to science. It belongs to the C. borneensis-group, a clade of ants often associated with Macaranga ant-plants in Southeast Asia. What makes C. indosinensis unusual within this group is its distinct size polymorphism, the largest workers have heads about 1.7 times wider than the smallest workers. This polymorphism is rare among Macaranga-associated Crematogaster species. The species can be distinguished from relatives by its developed subpetiolar process (a small projection under the petiole) and its head being wider than long ^[1].

The type locality is in Kampong Thom Province, Cambodia, at coordinates 12°34′N,105°23′E. All known specimens were collected in January 2010 from natural forest permanent sample plots. The species name 'indosinensis' refers to the Indochina region where it was found.

Appearance and Identification

Workers show dramatic size polymorphism, the smallest workers measure approximately 0.62mm in head width while the largest reach approximately 1.05mm. The head is slightly wider than long (cephalic index 102-107), which distinguishes it from other C. borneensis-group members. Large workers have a developed posterior portion of the head, while small workers have a more rounded head shape.

They have 10-segmented antennae with a 2-segmented club (the tip segments form a thickened antennal club). The body is red-brown in color. The propodeal spines are weakly developed as short processes. The subpetiolar process is developed, which is a key distinguishing feature from similar species Crematogaster borneensis and Crematogaster decamera. Overall, the ants appear smooth and shining with sparse standing hairs on the dorsal surfaces ^[1].

Distribution and Habitat

This species is currently known only from its type locality in Cambodia, Kampong Thom Province. This makes it one of the most restricted ant species in terms of known distribution. The area is in tropical Southeast Asia with natural forest habitat.

The specimens were collected from permanent sample plots established by the Cambodian Forestry Administration, which are scientific monitoring areas within natural forest. Workers were foraging on lower vegetation, suggesting they search for food in the understory layer of the forest. Whether they have a mutualistic relationship with ant-plants (like many related Crematogaster species do with Macaranga plants) is currently unknown ^[1][2].

Keeping This Species in Captivity

Because this is a newly described species with essentially no captive care history, keeping C. indosinensis requires a patient, experimental approach. Start with standard Crematogaster care as a baseline: a nest that retains some moisture (Y-tong/plaster works well), moderate humidity, and temperatures in the low-to-mid 20s°C.

Since exact dietary preferences are unknown, offer a variety of foods including sugar sources (honey water, sugar water) and protein (small insects like fruit flies, pinhead crickets, or mealworms). Monitor what they accept and adjust. The small worker size means escape prevention should be adequate, they can slip through small gaps.

The biggest challenge is that this species has never been kept in captivity before. Expect to learn as you go and document your observations carefully. If you obtain a colony, tracking its development, preferred foods, and behavior would contribute valuable knowledge to the antkeeping community.

Phylogenetic Position

Molecular analysis using COI gene sequences places Crematogaster indosinensis as the sister group to all other members of the C. borneensis-group, with 100% posterior probability and 100% ML bootstrap support. The COI divergence from C. borneensis is 20.0% (K2P distance), which is relatively high and suggests a long period of separation, estimated at 5-13 million years ago based on standard molecular clock rates.

This phylogenetic position makes C. indosinensis evolutionarily significant within its group. The species represents an early branch in the C. borneensis-group lineage, which may explain some of its unique features like the size polymorphism not seen in other group members ^[1].

Frequently Asked Questions

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References