Strongylognathus testaceus

Quick Summary

• Difficulty: Expert
• Origin & Habitat: Found across Central and Southern Europe, the Caucasus, Anatolia, southwestern Siberia, and northern Kazakhstan ^[8][5]. Inhabits warm, dry habitats such as steppe grasslands, pine forests, rocky slopes, heathlands, calcareous grasslands, and open forest edges ^[9][10]. Prefers moister microsites within the host's dry range, often under flat stones or in small earth mounds ^[9].
• Colony Type: Queen‑tolerant inquiline, the parasite queen lives alongside the host Tetramorium queen without killing her ^[11][4]. Mixed colonies contain both species' workers, but S. testaceus workers typically make up only 1-5% of the total worker population (rarely up to 7.5%) ^[12][10]. Nests can have one to five parasite queens (mono‑ or oligogynous) ^[13].
• Size & Growth:
  • Queen: 3.2-4 mm ^[10]
  • Worker: 2.0-3.6 mm ^[1]
  • Colony: Up to 20,000 individuals (mixed colony) ^[14]
  • Growth: Slow
  • Development: Unknown, occurs within the host colony and has not been specifically studied, new parasite workers typically appear several months after the queen’s introduction ^[1]. (Development is slow because host workers prioritize their own brood.)
• Antkeeping:
  • Temperature: Keep at 20-24°C, similar to the host's preferences. Avoid extremes. Inferred from host biology ^[14].
  • Humidity: Moderate to slightly dry. The host Tetramorium caespitum prefers dry to moderately damp conditions, so provide a gradient ^[14].
  • Diapause: Unknown, but because both host and parasite are temperate, a winter rest period (2-3 months at 5-10°C) is likely needed. Based on host patterns.
  • Nesting: Cannot be kept without a host Tetramorium colony. Natural nests are found under flat stones or in small earth mounds in warm, sunny locations, often at forest edges or in open grassland with some moisture ^[9].
• Behavior: Extremely docile and passive inside the nest. S. testaceus workers cannot feed themselves and rely completely on host workers ^[1]. They show little activity and do not participate in foraging, nest maintenance, or brood care ^[15]. When provoked, they may attack intruders but are too weak to cause harm ^[16][17]. Escape risk is low due to their inactivity and small size.
• Common Issues: This species cannot survive without a host Tetramorium colony, attempting to keep it alone leads to starvation and death., Maintaining two species simultaneously is extremely difficult, you need a large, healthy host colony first., Introducing the parasite queen is risky, host workers may reject and kill her initially ^[10]., S. testaceus workers are nearly non‑functional, they cannot feed, forage, or clean and must be hand‑fed by host workers., Obtaining a mated queen is extremely hard, the species is rare and cryptic, and protected in many countries., The species is endangered or threatened across much of its range (e.g., Flanders, Austria, Belgium), always check local laws before collecting ^[20][22].

Understanding the Parasitic Lifestyle

Strongylognathus testaceus represents an evolutionary intermediate between true slave‑makers and permanent social parasites (inquilines). Unlike slave‑making ants that raid other colonies for pupae, this species has lost the ability to raid entirely ^[4]. The parasite queen enters a Tetramorium nest and is accepted by the host workers. She does not kill the host queen but instead uses pheromones to suppress the host’s production of sexual offspring ^[7]. Both queens coexist, laying eggs that host workers rear. The resulting S. testaceus workers are fed and cared for by host workers but contribute almost nothing to colony function, they cannot feed themselves, forage, or build nest structures ^[15][1]. This species is often called a 'degenerate slave‑maker' because it evolved from slave‑making ancestors but has since lost its raiding instinct ^[18]. The worker caste is so reduced that it is on the path to eventual disappearance ^[19].

The Critical Host Requirement

This cannot be stressed enough: Strongylognathus testaceus cannot survive without a host Tetramorium colony. You must first establish a healthy colony of Tetramorium caespitum, T. impurum, or one of the other recorded hosts (T. semilaeve, T. alpestre, T. moravicum, T. ferox, T. brevicorne) before attempting to keep the parasite ^[6][5]. The host colony provides all essential functions, foraging, nest maintenance, brood care, and feeding both queens and their offspring. In mixed colonies, S. testaceus workers typically make up only 1-5% of the total worker population, rarely reaching 7.5% ^[12][10]. Host workers raise the parasite’s brood alongside their own. If the parasite queen dies, the host queen continues producing workers normally. If the host queen dies, the colony is unlikely to survive long. This species is NOT suitable for beginners, it requires advanced antkeeping skills and the ability to maintain two species simultaneously.

Colony Foundation and Introduction

In the wild, colony foundation occurs when a newly mated S. testaceus queen joins a founding Tetramorium queen. Observations from ant keepers show that the Tetramorium queen licks and grooms the smaller parasite queen, likely helping her acquire the colony’s chemical signature ^[14]. The nuptial flights occur from July to September, with parasite queens swarming simultaneously with their host species or a few days later ^[7][10]. To establish a mixed colony in captivity, you would need to introduce a mated S. testaceus queen into an established Tetramorium colony. The introduction process can be stressful, host workers may initially reject and attack the intruder, but the parasite queen often persists until accepted ^[10]. Successful colonies have been reported where both species’ queens cooperate and produce workers. Alternatively, the parasite queen can be kept with a host queen alone in a test tube, and host workers will later join ^[14].

Feeding and Nutrition

S. testaceus workers cannot feed themselves and must be fed by host workers ^[1]. This means you do not directly feed the parasite ants, you feed the host colony, and the host workers distribute food to both species. The host Tetramorium workers are omnivorous, accepting sugars (honey water, sugar water), protein sources (insects, small prey), and seeds ^[14]. The host workers will prioritize feeding their own queen and brood, but they also feed the parasite queen and her offspring. In laboratory observations, S. testaceus workers showed no interest in food items, they only briefly contacted prey with their antennae but did not consume anything ^[1]. This complete dependence on host workers is why the parasite workers are considered 'useless' to the colony.

Legal and Ethical Considerations

Strongylognathus testaceus is a protected species in many European countries and is considered endangered or threatened in several regions ^[20][21]. In Belgium, it is considered extinct in Wallonia and endangered in Flanders ^[22]. In Austria, it is classified as threatened ^[23]. Before attempting to keep this species, check your local regulations regarding the collection and possession of native parasitic ants. The species has declined significantly due to habitat loss and the decline of its host species. If you do find a mixed colony in the wild, collecting should be done responsibly and with permission. Given the extreme difficulty of maintaining this species and its protected status, it is generally not recommended to keep S. testaceus in captivity unless you are an experienced researcher or conservationist working with proper permits.

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References