Scientific illustration of Solenopsis xyloni (Southern Fire Ant) - showing key identification features including head, thorax, and gaster.

Southern Fire Ant

Solenopsis xyloni

Monogynous Polygynous species.list.optionally polygynous Non-Parasitic Queen No Gamergate
Sci. Name
Solenopsis xyloni
Tribe
Solenopsidini
Subfamily
Myrmicinae
Author
McCook, 1880
Common Name
Southern Fire Ant
Distribution
Found in 2 countries
Nuptial Flight
From June to August
Peak flight Time
21:00
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Introduction

Solenopsis xyloni, commonly called the southern fire ant or native fire ant, is a North American species that belongs to the Solenopsis geminata species group . Workers are 3.2-6.4 mm long with a distinctive bicolored pattern: reddish to orange-brown head and thorax with a black abdomen, though some populations are entirely dark . They nest in open areas in soil or under stones, often creating irregular crater-shaped mounds with multiple entrances . Their range extends throughout the southern United States and into Mexico, from California east to the Carolinas and south through the southwestern states and northern Mexico . In Nevada, they occur in the Hot Desert region from -160 ft in Death Valley to 4500 ft near Beatty . These ants are aggressive foragers with a painful sting (rated 1 on the Schmidt pain scale), though notably less aggressive than the introduced red imported fire ant (Solenopsis invicta) . They are generalist feeders, consuming proteins, sweets, seeds, and actively raiding colonies of other ant species including Pheidole, Pogonomyrmex, and Veromessor . In their native range, they play ecological roles as predators and seed dispersers, but can also become kitchen pests and cause damage to lawns and agricultural settings . They have been displaced from much of their southeastern range by the invasive Solenopsis invicta .

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Status by country, from Kass et al. 2022 & Wong et al. 2023

Native Invasive Introduced (indoor) Intercepted Unknown
2000 - 2026

Quick Summary

  • Difficulty: Expert
  • Origin & Habitat: Native to the southern United States and Mexico, ranging from California to the Carolinas. Found in hot desert regions, open grasslands, pastures, and disturbed areas with exposed soil. In Nevada, occurs in the Hot Desert region from -160 ft in Death Valley to 4500 ft near Beatty [3][11].
  • Colony Type: Both monogyne (single-queen) and polygyne (multiple-queen) colonies occur naturally. Single-queen colonies are more common, but multiple-queen colonies have been documented [4][12]. Queens are winged and mate during nuptial flights.
  • Size & Growth:
    • Queen: Size data unavailable, only worker sizes are documented in the literature.
    • Worker: 3.2-6.4 mm (1/8 to 1/4 inch) [2], with a mean body length of 3.1 mm [8]
    • Colony: Unknown for this species specifically. Colonies can have over 40 nest openings [4]. Based on related fire ants, colonies may reach several thousand workers.
    • Growth: Moderate (estimated from related Solenopsis species)
    • Development: Unknown, no species-specific data. Related Solenopsis invicta develops in about 3-5 weeks under optimal conditions. (Development is temperature-dependent, warmer temperatures accelerate brood development.)
  • Antkeeping:
    • Temperature: Keep nest area at 24-30°C. This is a hot-climate specialist that tolerates high temperatures: LD50 at 44.55°C (0% RH) and 42.63°C (100% RH) [13]. Provide a temperature gradient so workers can self-regulate.
    • Humidity: Provide a humidity gradient. In lab studies workers strongly prefer 100% RH over 50% [13], but they naturally inhabit arid regions and tolerate dry conditions. Keep the nest substrate moderately moist in one area while allowing other zones to remain dry.
    • Diapause: Likely requires a winter diapause based on its temperate distribution. Reduce temperature gradually to 10-15°C for 3-4 months (as typical for North American temperate ants). Specific conditions are unconfirmed for this species.
    • Nesting: Use a naturalistic setup with soil or sand substrate, or a Y-tong/plaster nest with chambers scaled to size. Provide damp substrate for brood areas but allow some drier zones. Multiple entrance tubes are recommended as they prefer multiple nest openings [4].
  • Behavior: Highly aggressive when their colony is disturbed. Workers swarm rapidly and deliver painful stings (pain rating 1 on the Schmidt scale) [7]. They raid other ant colonies and dominate food sources [8][14]. Escape risk is moderate due to their small size (3-6 mm), use tight-fitting barriers. They are primarily outdoor ants but can nest indoors in wall voids, especially in Arizona [15].
  • Common Issues: sting pain can be severe for sensitive individuals, handle with extreme caution, use long forceps or aspirators., aggressive defense when colony disturbed increases escape risk, always work in a secondary containment tray., nearly eliminated from most of southeastern USA by invasive Solenopsis invicta, wild colonies are now hard to find in many areas [10]., microsporidian parasite Kneallhazia solenopsae has been found in S. geminata × S. xyloni hybrids [15], may affect colony health., they are omnivorous and may tend aphids for honeydew, attracting other pests if colonies are kept indoors [17].
Nuptial Flight Activity Analysis 573 observations
Jan
Feb
Mar
Apr
May
147
Jun
165
Jul
116
Aug
Sep
Oct
Nov
Dec

Solenopsis xyloni follows a consistent seasonal pattern with peak activity in July. The flight window runs from June to August, providing several months of opportunity for observations.

Flight Activity by Hour 573 observations
00:00
01:00
02:00
03:00
04:00
05:00
06:00
07:00
13
08:00
09:00
17
10:00
15
11:00
17
12:00
19
13:00
18
14:00
14
15:00
23
16:00
29
17:00
69
18:00
83
19:00
60
20:00
86
21:00
26
22:00
25
23:00

Solenopsis xyloni nuptial flight activity peaks around 21:00 during the night. Activity is spread across a 16-hour window (08:00–23:00). A secondary activity peak occurs around 19:00. Times may be influenced by human observation patterns.

Temperature and Care

Solenopsis xyloni is a hot-climate specialist that tolerates high temperatures better than most ants. Keep the nest area at 24-30°C, with a gradient so workers can move between warmer and cooler zones. They can survive temperatures up to 44°C in dry conditions and 42°C in humid conditions [13]. Use a heating cable on one side of the nest to create the gradient. During winter, reduce temperature gradually to 10-15°C for 3-4 months to simulate the natural seasonal cycle. This species is more tolerant of dry, hot conditions than the invasive red fire ant, making it well-suited to desert environments [16].

Feeding and Diet

These ants are generalist feeders with a varied diet. They accept protein sources (insects, mealworms, crickets) and sweets (sugar water, honey). They are known to raid colonies of other ant species including Pogonomyrmex and Pheidole [8]. They also collect seeds and tend aphids for honeydew [17]. Feed protein 2-3 times per week and provide constant access to sugar water. In captivity, they accept most standard ant foods but should have a varied diet for optimal colony health. They can also scavenge dead insects [18].

Nesting Preferences

In the wild, S. xyloni nests in open areas in soil or under stones, creating irregular crater-shaped mounds with multiple entrances [4]. They prefer bare, exposed ground and are common in disturbed areas, lawns, and roadsides [15]. For captivity, use a naturalistic setup with a sand/soil mixture, or a Y-tong/plaster nest with appropriately sized chambers. Provide multiple exit tubes because they naturally have multiple nest entrances. Keep the substrate moderately moist in one section but allow other zones to dry out to mimic natural conditions.

Behavior and Temperament

This species is aggressive and defends its colony vigorously. Workers deliver painful stings rated 1 on the Schmidt pain scale [7]. When disturbed, colonies become highly agitated with workers rapidly swarming. They are group foragers that typically travel 3-4 m from nest entrances [8]. They raid and displace other ant species and can dominate food sources. Their colonies may be polydomous (multiple connected nest sites) [18]. They show greater aggressiveness toward larger ant species than toward similarly-sized threats [14]. Handle with extreme caution, never handle with bare hands.

Nuptial Flights and Reproduction

Nuptial flights occur from June through September, primarily in the late afternoon [4]. Males and females emerge from the nest in large numbers, often preceded by aggressive activity around nest entrances [3]. Mated queens establish new colonies independently in soil, sealing themselves in to raise the first brood (claustral founding) [4]. Reproductives can be found in the nest throughout the year [3]. After mating, queens lose their wings and dig into the ground to start a colony.

Defense Mechanisms

Solenopsis xyloni possesses a functional stinger and delivers venom containing piperidine alkaloids [19]. The major venom components are cis-C11 and trans-C11 piperidines in a roughly 4:1 ratio [19]. The sting causes immediate pain followed by a flare and wheal, but pustules rarely form (unlike Solenopsis invicta) [4]. Venom also has antibacterial and antifungal properties [4]. When threatened, workers swarm aggressively and sting repeatedly. They are more aggressive toward larger ant species like Pogonomyrmex rugosus than toward similarly sized threats [14].

Frequently Asked Questions

Does Solenopsis xyloni sting?

Yes, they sting and it is painful. The sting is rated 1 on the Schmidt pain scale (relatively mild compared to other fire ants) [7]. Unlike the invasive red imported fire ant, S. xyloni stings rarely form pustules [4]. However, they are aggressive defenders and should never be handled with bare hands.

How long does it take for first workers to appear?

This is not specifically documented for S. xyloni. Related fire ant species like Solenopsis invicta develop from egg to worker in about 3-5 weeks at optimal temperatures (around 27°C). Expect a similar timeframe but no precise data is available.

Can I keep multiple queens together?

Solenopsis xyloni does form both single-queen (monogyne) and multiple-queen (polygyne) colonies in the wild [4][12]. However, combining unrelated foundresses is risky and not recommended for beginners. If you try a multi-queen setup, introduce queens before either has laid eggs and provide plenty of space.

What do southern fire ants eat?

They are generalists: proteins (insects, mealworms, crickets), sweets (sugar water, honey), and seeds [17][9]. They also raid other ant colonies. Feed protein 2-3 times per week and provide constant access to sugar water.

Do they need hibernation?

Likely yes, because they are native to temperate North America. Reduce temperature gradually to 10-15°C for 3-4 months during winter. This mimics their natural seasonal cycle and supports long-term colony health. Specific conditions have not been studied for this species.

Are they good for beginners?

No, this species is not recommended for beginners. Their painful sting, aggressive behavior, and tendency to escape make them challenging. Also, they are hard to find in the wild because Solenopsis invicta has displaced them from much of their historic range [10]. Only experienced keepers familiar with aggressive species should attempt to keep them.

Why are they called southern fire ants?

They are called fire ants due to their painful sting that feels like a burn. They are the native North American fire ant, as opposed to the introduced red imported fire ant (S. invicta) which is more aggressive and has displaced S. xyloni from much of its former range [3].

How big do colonies get?

Colony size is not well documented. Mounds with over 40 nest openings have been reported [4], suggesting colonies can be quite populous. Based on related fire ant species, colonies likely reach several thousand workers at maturity.

What temperature range do they tolerate?

This species is highly heat-tolerant: they survive up to 44°C in dry conditions and 42°C in humid conditions [13]. Keep them at 24-30°C for optimal growth. They can tolerate cooler temperatures during winter (10-15°C) but should not be kept cold year-round.

When is the nuptial flight of Solenopsis xyloni?

The nuptial flight of Solenopsis xyloni typically occurs From June to August.

What time of day does Solenopsis xyloni fly?

The nuptial flight of Solenopsis xyloni peaks around 21:00 during the night, with most activity between 08:00 and 23:00. Times may be influenced by human observation patterns.

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References

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