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Bug of the Week is written by "The Bug Guy," Michael J. Raupp, Professor of Entomology at the University of Maryland.

Carbo-loading here and there: Odorous house ants, Tapinoma sessile, and harvester ants, Pogonomyrmex


Odorous house ants circle for their last meal, a lethal drink of sugary bait laced with poison.


At the start of a new year the media is replete with dietary advice. This year sugar and some starches are on the no - no list. But to many members of the insect world, carbohydrates are definitely on the menu. Last week we visited carpenter ants here and there. This week we continue our adventures with ants here and there, first in Maryland, then to the deserts of the American southwest to see how different kinds of ants balance their food pyramids, gathering simple and complex carbohydrates.  

Here: Odorous house ants have become a perennial guest at Bug of the Week as these small brown ants invade homes throughout our region each spring. This ant earns its name by virtue of the distinctive smell it makes when crushed between fingers or on a counter. The odor is reminiscent of slightly fermented coconuts. In the wild, odorous house ants seek rich sources of sugars such as the sugary honeydew produced by aphids or scale insects. Once scouts discover the food source, they establish a trail marked by chemicals called pheromones. The trail leads other workers from the colony to the bounty. Outdoors, odorous house ants nest beneath stones or fallen logs. I usually have several colonies in my yard in a woodpile or under stones in a wall. Their quest for food brings them into homes and a few grains of sugar on the counter or a leaky bottle of pancake syrup in the pantry will often initiate a full-scale invasion by foragers.



Following a pheromone trail invisible to humans, an odorous house ant arrives at a droplet of syrup on my counter to tank up with her colony mates.

To foil these raiders, first eliminate as many sources of food as possible. Clean the counters, mop up drips, and get pet food off the floor after your pets have eaten. Be sure that no syrup or sweets are spilled or leaking in your cupboards. If you find ants and their telltale trails on counters or along baseboards, try to locate the source of food and clean it up and then follow the trail back to the point of entry into your home. Ant trails on the counter or floor can be disrupted by spraying them with household cleansers. You can buy ant traps or purchase tubes of liquid or gelatin ant baits. Place ant traps or baits at locations indicated on the label. I usually place one near the point of entry to my home and several others around my counters and near their raiding columns. The traps and baits contain a lure that attracts ants searching for sweets or fatty foods. The lure contains poison. Workers ingest the toxin and are killed, or in some cases they carry the toxic treat back to the colony and feed the deadly meal to the queens and their nest mates and, voilà, the royals are assassinated and the colony with them. A few well-placed bait stations in my kitchen put an end to the ant trails in a matter of days.

There: Our next stop is 2,000 miles west and south of Maryland in the deserts of Utah to visit red harvester ants. In addition to simple sugars like those found in nectar and honeydew of aphids, many ants thrive on long chain and complex carbohydrates found in the seeds of plants. Red harvester ants get their name by harvesting seeds that serve as the major source of food for their colony. Each morning patroller ants emerge from the entrance of the colony and inspect the area immediately around the colony and at distances up to a 20 minute ant-walk away. The return of morning patrollers sends a signal to the colony to muster forager ants and begin the busy task of collecting seeds from nearby plants. These dauntless foragers may spend up to an hour and venture 20 meters from the colony in search of seeds to bring back to subterranean granaries of their colony.



Red harvester ant foragers return to the colony with the goods an amazing 90% of the time.

Seed harvesting is not entirely bad for desert plants as some seeds are lost along the way during peregrinations of foragers. Some accounts tell of seeds sprouting in over-filled harvester ant galleries giving rise to new plants. Either way, harvester ants are important seed dispersal agents for propagules of many different species of plants. In fact, some plants have taken this relationship to a higher level and produce seeds with appendages and chemicals that attract ants for the purpose of dispersal. This form of ant assisted seed dispersal is known as myrmecochory. Red harvester ants are also known by many as the entertaining occupants of “ant farms” sold to children and schools. Ant farms are engaging and educational but as some have learned firsthand, harvester ants pack a memorable sting. So, in this New Year go light on the simple sugars and be more like harvester ants and favor whole grain foods.


Two excellent ant references, “The Regulation of Foraging Activity in Red Harvester Ant Colonies” by Deborah M. Gordon, and “The Ants” by Bert Hölldobler and E. O. Wilson, were used to prepare this episode.