Aphaenogaster picea – A Seed Dispersal Ant

Phylum: Arthropoda    Class: Insecta    Order: Hymenoptera
Family: Formicidae

Species Status in Ontario: genus Aphaenogaster worker ants are abundant
in North American hardwood forests

Image of digital stock illustration, North American ant, Aphaenogaster picea, Colour, 2019 © Suzanne M Matheson.
Aphaenogaster picea, Colour, 2019 © Suzanne M Matheson

Family, Formicidae:
This is the highly social insect family we know as ants. They evolved from vespoid wasp ancestors during the Cretaceous period and became more diverse after the proliferation of flowering plants. They are distinguished by “elbow” antennae and the distinct node-like structure forming their slender waist.

Ants live in colonies that range significantly in size depending on the species. The larger colonies have a caste structure, consisting of sterile, wingless worker and soldier females, a much smaller number of fertile “drone” males, and one or more fertile female “queens”. Superorganism is a term used to describe an ant colony, as the ants appear to operate as a unified whole.

Apart from Antarctica and a few remote islands, family Formicidae has colonized every landmass on Earth. It is believed that this family makes up 15-25% of the Earth’s terrestrial animal biomass. Besides social organisation, their ability to modify habitats, tap resources and defend themselves accounts for their vast presence. As a result of their long co-evolution, ants have developed various types of relationships with other species, including relationships termed mimetic, commensal, parasitic, and mutualistic.

Genus, Aphaenogaster:
Aphaenogaster is a large, diverse genus, found throughout the world, with exceptions being southern South America, southern Africa, Antarctica and a few remote, inhospitable islands.

I find the North American species elegant. They have an elongate and slender habitus (general appearance), with a head that is usually longer than broad. Their large, convex eyes are placed on the head at the middle. The dorsal portion of the workers’ mesothorax (mesonotum) is elongate and depressed. The first abdominal segment, fused with the thorax to form the mesosoma (propodeum), usually has a pair of spines or small teeth. The antennal club, consisting of four segments, is poorly defined.

Pen & ink illustration of the lateral, head and dorsal perspectives of Aphaenogaster picea ant, 2019 © Suzanne M Matheson.
Lateral, head and dorsal views of Aphaenogaster picea ant, 2019 © Suzanne M Matheson

Description/Morphology:
Aphaenogaster picea is named for its dark red/brown coloration. The ants you are most likely to see above ground, the workers, are 4-6 cm, while their queen is 7-8 cm. This species is very similar to A. rudis, but can be easily distinguished by the antennae, ending in a 4-segmented club that is lighter in colour. As well, A. picea workers have a lighter, some say “yellow” tipped, gaster (the bulbous posterior portion of the metasoma or abdomen).

Colour illustration with labelled parts, demonstrating the biological morphology of Aphaenogaster picea ant, 2019 © Suzanne M Matheson.
Biological morphology of Aphaenogaster picea ant, 2019 © Suzanne M Matheson

Range:
A. picea is an ant of northeastern North America, commonly found in eastern United States and eastern Canada. It has also been found in some Se states and Mexico.

Habitat:
This arboreal species is found in a wide range of forest habitats. While she prefers nesting in downed wood and old stumps, as an opportunist the gyne (queen) will nest under bark, under objects on the ground, in soil, or in any cavity with a suitable range of temperature and adequate protection. For this monogyne (having one queen) colony, leaf litter is an important element of its microhabitat.

Behaviour/Life Cycle:
A. picea are mostly diurnal, though they will also forage at night. Omnivorous forages, their preferred diet is insects, including termites, fruit flies, crickets, meal worms, and wax worms. Curiously, they refuse liquids, often covering up liquid sources.

Hibernation is accomplished by means of anti-freeze in their blood. The slow climate cool down activates this substance. In the wild they can survive extreme cold.

In terms of mating, their major flight is in August, after a light rain, though they have been known to fly before and after this summertime month.

Fertilized females will overwinter. In the spring, after egg-laying it takes 10-15 days for the larvae to form. Another 15-20 days are needed for their pupal transformation. They do not utilize a cocoon. Pupae become workers in yet another 15-20 days. The lengths of time are determined by temperature.

The forest benefits by the seed dispersal activity of this arboreal species. Enticed by the nutrient-rich elaiosome encasement of the diaspore (seeds of some plants, contained within a food-body), the workers carry these seeds back to their nest. This food source, rich in both lipids and oleic acid, is desirable for their developing larvae. While eating away the elaiosomes, the larvae do not injure the seeds. Once stripped, the seeds are discarded from the nest or cached in a midden underground. Away from the parent plant, protected from predators, the seeds, cast-away into soil made rich by the lifestyle of the ants, grow into new plant colonies.

Watercolour painting of seed dispersal ants, Aphaenogaster picea carrying Trillium grandiflorum diaspore across a bed of Plagiomnium ciliare and Ctenidium molluskum mosses, 2019 © Suzanne M Matheson.
Watercolour painting, Myrmecochory, 2019 © Suzanne M Matheson

“Myrmecochory” depicts seed dispersal ants, Aphaenogaster picea, carrying diaspore
of myrmecochorous plant, Trillium grandiflorum (Large-flowered Trillium),
across a bed of Plagiomnium ciliare (Saber Tooth acrocarp) and
Ctenidium molluscum (Feather Comb pleurocarp) mosses.

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Dispersive Mutualism:
In terms of ecology, mutualism, one of several different types of symbiotic relationships, refers to one in which both species benefit. In traditional Indigenous sciences, such a relationship is seen as part of the gift-reciprocity networks and cycles. “Dispersive” mutualism is a relationship in which one species receives food in return for the transport of the other species’ offspring. In the case of bees and flowers, this would be “pollination”, nectar in exchange for pollen distribution. In the case of A. picea ants and some plants, this would be “myrmecochory”, elaiosome (food bodies) as larval nutrition in exchange for seed dispersal.

Myrmecochorous plants produce diaspore, seeds encased in nutrient-rich elaiosome, in order to attract ants for the purpose of having their seeds dispersed. From Ancient Greek, myrmecochory means, “circular dance”. Trillium grandiflorum (Large-flowered Trillium) is one such plant who joins in this beautiful circular dance with genus, Aphaenogaster.

Other Associations:
This ant, A. picea, is a preferred prey of Plethodon cinereus (Eastern Red-backed Salamander), also common in Ontario’s mesic woodlands.

To learn more about myrmecochory and the species mentioned in this blog, follow The Forest Project blog

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Bibliography:

Asch, Michael, John Borrows, & James Tully. Resurgence and Reconciliation Indigenous-Settle Relations and Earth Teachings. Toronto, Ontario: University of Toronto Press, 2018.

Lubertazzi, David. (2012). The Biology and Natural History of Aphaenogaster rudis. Psyche. 2012.
10.1155/2012/752815.

On-line Resources:

“Ant.” Wikipedia. Updated 19 July 2020. Web. Accessed 27 July 2020. https://en.wikipedia.org/wiki/Ant.

AntWeb. Version 8.40.2. California Academy of Science. Web. Accessed 27 July 2020. https://www.antweb.org.

“Aphaenogaster.” Ant Wiki. Updated 27 July 2020. Web. Accessed 27 July 2020. https://antwiki.org/wiki/Aphaenogaster#Worker_Morphology.

“Aphaenogaster picea.” Ant Wiki. Updated 24 July 2020. Web. Accessed 27 July 2020. https://antwiki.org/wiki/Aphaenogaster_picea.

“Eastern Red-backed Salamander Plethodon cinereus.” Ontario Nature. Web Accessed 24 Oct 2019.
https://ontarionature.org/programs/citizen-science/reptile-amphibian-atlas/eastern-red-backed-salamander/.

“Five Types of Ecological Relationships.” Nguyen, David H. Ph.D. Seattle Pi. Web. Accessed 27 July 2020. https://education.seattlepi.com/five-types-ecological-relationships-4019.html.

“Mesonotum.” Fine Dictionary. Web. Accessed 27 July 2020. http://www.finedictionary.com/Mesonotum.html.

“Myrmecochory.” Wikipedia. Updated 13 Feb 2020. Web. Accessed 27 July 2020. https://en.wikipedia.org/wiki/Myrmecochory#:~:text=Myrmecochory%20(%2Fm%C9%9C%CB%90rm%C9%AA,plant%20interaction%20with%20worldwide%20distribution.

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