Novomessor ensifer

Novomessor ensifer

Novomessor ensifer is a large, striking ant species native to western Mexico. Workers measure 8-10mm and have a distinctive reddish-brown coloration with a darker brown abdomen. They feature notably long propodeal spines averaging 1mm in length and a head that is longer than wide. These ants inhabit arid scrub-thorn forest on the Pacific slope below 5000 feet elevation, from northwestern Jalisco to Guerrero. They nest in soil containing large stones buried in coarse sand, typically positioning their nests under rocks rather than building visible craters. Unlike their seed-harvester relatives, N. ensifer is strictly insectivorous, with dead insects forming the bulk of their diet, no plant material has ever been found in their nests.

Quick Summary

• Difficulty: Medium
• Origin & Habitat: Western Mexico (Colima, Guerrero, Hidalgo, Jalisco, Michoacán) in arid scrub-thorn forest below 5000 feet on the Pacific slope ^[1][2][3]
• Colony Type: Likely monogyne (single queen colonies) based on typical genus patterns. Incipient colonies consist of one dealate queen with 31 workers ^[2].
  • Colony: Monogyne
• Size & Growth:
  • Queen: Larger than workers, exact measurements unconfirmed for this species
  • Worker: 8-10mm ^[3][2], large for a Myrmicinae ant, approximately twice the size of typical North American Aphaenogaster
  • Colony: Colonies reach large sizes with multiple galleries 3-8 inches in diameter under buried stones ^[2]
  • Growth: Moderate, incipient colony with 31 workers suggests steady growth
  • Development: Unknown, no direct development data exists. Based on related Aphaenogaster species and tropical location, estimate 6-10 weeks at optimal temperature. (Small workers (nanitics) from first brood measure 5.56-6.50mm and are notably smaller than mature workers. Later broods develop into large workers (7.28-9.63mm) ^[2].)
• Antkeeping:
  • Temperature: As a xeric species from tropical western Mexico, keep them warm. Aim for 24-30°C, with a slight gradient allowing workers to self-regulate. Avoid temperatures below 20°C ^[3].
  • Humidity: Low to moderate, these ants inhabit arid scrub-thorn forest. Keep nest substrate relatively dry with occasional moisture zones. Avoid damp, stagnant conditions ^[2][3].
  • Diapause: Unconfirmed, given their tropical distribution in western Mexico, they likely do not require true hibernation. However, a slight cooling period during winter months may be beneficial ^[3].
  • Nesting: In nature they nest under stones in coarse, stony soil with galleries forming around buried stones. In captivity, provide a naturalistic setup with a mix of sand and small stones, or a Y-tong/plaster nest with coarse substrate. They need deeper spaces (passageways extend 7+ inches) and prefer narrow chambers scaled to their large size ^[2].
• Behavior: Workers are active foragers throughout the day but reduce activity during peak midday heat (95-100°F). They forage most actively in early morning (9-11 AM) and late afternoon (3-5 PM), searching for dead insects up to 25 feet from the nest. They forage singly rather than in groups, and when multiple workers find food, they show 'noticeable lack of cooperation', each pulls in a different direction, sometimes tearing the food apart. This is not aggressive behavior toward each other, just disorganized foraging. Workers do not sting and are not particularly aggressive toward keepers. Their large size and long spines make escape prevention straightforward, standard barriers work well ^[2].
• Common Issues: stony soil requirement, they need coarse, rocky substrate to thrive, pure sand or compact soil won't work, strictly insectivorous, do not offer seeds or sugar, they will not accept plant-based foods, deep nesting, they need vertical space for galleries extending 7+ inches, shallow setups may stress them, heat sensitivity, midday foraging drops significantly, ensure cooler zones exist in the setup, colony founding can be slow, incipient colonies already had 31 workers suggesting extended founding period

Natural History and Distribution

Novomessor ensifer is endemic to western Mexico, found in the states of Colima, Guerrero, Hidalgo, Jalisco, and Michoacán ^[1]. Their habitat consists of basins and low mountains on the Pacific slope between the pine-oak forest on the interior mountains and the Pacific Ocean. This region experiences a wet season in late summer and fall, with a dry spring season. The terrain features soil made up of many large stones buried in rather coarse sand, this specific soil composition is essential for nest establishment. The ants occupy arid scrub-thorn forest below 5000 feet elevation, characterized by an upper stratum of shrubs and trees 15-25 feet tall (including Acacia and cacti like Lemaireocereus) with sparse ground cover of low herbs and grasses ^[2]. The species was previously known as Novomessor ensifer before being synonymized with N. ensifera ^[3].

Nest Construction and Preferences

In the wild, N. ensifer shows a strong preference for nesting under stones buried in coarse, sandy soil. They require both sand AND buried stones to establish nests, colonies are absent from areas lacking buried stones. The nest opening is a single hole 1-4 inches in diameter, located at the side of a stone or between two stones. Unlike many ant species, they do not build craters of excavated soil around their nest openings. Each nest has a single wide passageway descending almost straight down into the soil, which widens under stones to form irregular galleries 3-8 inches in diameter for brood. The passageway continues deeper, with galleries forming wherever stones are encountered. One nest was excavated to 15 inches depth with no evidence of horizontal branching, these ants need significant vertical space ^[2]. For captive care, recreate this with a naturalistic setup containing coarse sand and small stones, or a deep Y-tong/plaster formicarium with rocky substrate.

Feeding and Diet

Unlike most related seed-harvester ants in the genus Veromessor, Novomessor ensifer is strictly insectivorous. No seeds have ever been found stored in their nests, and no workers have been observed gathering seeds. Dead insects provide the bulk of their diet, parts of dead insects were found in several nests during field studies. One observation documented workers bringing back a dead ichneumon fly, a bembicine wasp, and a small moth to their nest. Living mites and collembolans were also collected in one nest, though their status (food or accidental hitchhikers) was not determined ^[2]. In captivity, feed them dead insects such as mealworms, crickets, and other small arthropods. They do not need sugar or honey, their diet is purely protein-based. Feed protein prey 2-3 times per week, removing any uneaten prey within 24 hours.

Foraging Behavior

Workers forage throughout the day from 9:00 AM to 5:00 PM, but their activity is greatly diminished during midday when air temperatures reach 95-100°F. Peak foraging occurs in early morning (9-11 AM) and late afternoon (3-5 PM). Most foraging is done on the ground, though a few workers may climb on low vegetation without feeding on plants. Workers forage singly and often travel 25 feet or more from the nest. When a worker discovers a dead insect, it immediately starts pulling the food toward the nest. Other workers joining the find show a 'noticeable lack of cooperation', each worker attempts to pull the food in a separate direction, which sometimes results in the insect being torn apart, with each worker carrying a piece back to the nest. This chaotic group transport is a distinctive behavioral trait of this species ^[2].

Colony Structure and Development

A documented incipient colony consisted of one dealate (wingless) queen,31 workers,6 pupae,15 larvae, and 10 eggs. The nest opening was 1 inch in diameter with a passageway extending down 7 inches, containing three galleries under buried stones. Pupae were in the uppermost gallery while the queen and eggs were in the deepest gallery, this vertical separation of brood stages is notable. When discovered, the queen attempted to abandon the nest while workers focused on picking up the brood rather than protecting her. Small workers in this colony (likely the first brood) measured 5.56-6.50mm, notably smaller than mature workers. Small workers are rare or absent in larger nests, suggesting later broods develop exclusively into large workers ^[2]. Alate (reproductive) forms were absent in August and February collections, suggesting mating flights occur in spring or early summer ^[2].

Temperature and Seasonal Care

As a xeric species from tropical western Mexico, Novomessor ensifer prefers warm conditions. Their natural habitat experiences high temperatures, with midday air temperatures reaching 95-100°F during foraging hours. However, they avoid this peak heat by reducing activity during midday and foraging primarily in cooler morning and afternoon hours. In captivity, maintain temperatures between 24-30°C with a thermal gradient allowing workers to self-regulate. Provide a cooler zone (around 22-24°C) alongside warmer areas. Given their tropical distribution, they likely do not require true hibernation, but a slight reduction in temperature during winter months may be appropriate. Avoid temperatures below 20°C for extended periods. Heating cables or mats can be used on one side of the nest to create the necessary gradient. ^[3][2]

Identification and Morphology

Workers are large (8-10mm) with a distinctive appearance. The head is longer than wide, featuring a flange-like collar at the occiput similar to some Aphaenogaster species. They have large, triangular mandibles with three apical teeth. The mesosoma has long transverse rugae, and the propodeal spines are notably well-developed, averaging 1mm in length, approximately two-thirds to three-fourths as long as the dorsal surface of the epinotum ^[3][2]. Color is fairly constant: head and thorax are ferruginous (reddish), while the abdomen (gaster) is piceous brown. The legs and epinotal spines are clear yellowish red. The antennal scapes surpass the occipital margin by about one-third their length. Unlike some related species, N. ensifer lacks a psammophore (a basket of hairs for carrying sand) ^[4]. The gaster has a distinctive honeycomb-like pattern of minute polygonal ridged pits on its dorsal surface ^[2].

Frequently Asked Questions

References