Posted on: July 6, 2012
The following story originally appeared in the spring edition of Bridges, the magazine published by the TRU Alumni & Friends Association. —> View the pdf
By Mike Potestio
Virtually unnoticed by most of us, ants play an important role in the ecosystem as a food source, a pest controller and by adding nutrients to soil. With some recent discoveries by Dr. Robert Higgins, British Columbians may want to pay more attention to the ants at their picnic.
In the summer of 2010, North Vancouver residents contacted the city about ants that were swarming and stinging. The following winter Agriculture Canada sent samples to Higgins, an assistant professor and specialist in ant biology at TRU Williams Lake and one of only three entomologists in Canada specializing in identifying different species of ants. He identified them as the invasive Myrmica rubra, the European fire ant, which had not been documented in BC before.
“When new species, or something which is unusual turns up in Canada, it requires one of the three of us to do the identification work,” said Higgins. He has since identified European fire ant infestations in a community garden in Burnaby, the yards of two homes in Victoria, and two locations seven kilometers apart in Vancouver.
Unlike most ants in BC, which rarely attack in great numbers, European fire ants are aggressive when it is warm, and will quickly swarm and sting all at once if their nests — often in lawnsand gardens — are disturbed.
Children and pets are at risk of being stung, as well as people mowing their lawns or gardening.
“I’ve had two reports now of individuals who’ve had to go to emergency because of fairly severe swellings associated with the stings,” said Higgins. He is concerned this species might move into a high value recreational park such as the one located near the North Vancouver infestation, and make it unusable, as has happened to parks in eastern North America where the ants are more widely established.
European fire ants enjoy wet, warm habitats, but this discovery marks the first time these ants have been found above the 49th parallel and they appear to be living on the edge of their environmental tolerance.
Since being introduced to North America in the early 1900s, the European fire ant has developed high densities of nests. While newly-mated fire ant queens in Europe fly away to initiate new nests, in nests like the one Higgins found in the Lower Mainland, virgin queens are mating on their home nest and walking to new nest sites, causing a greater concentration of nests. “In North Vancouver for example,” said Higgins, “in one home owner’s yard there was a nest every square meter, and in some places there were four in a single square meter.” This way fire ants overwhelm other competitors in the area. “There’s a pro and a con to that. The bad side is you get these heavy densities of nests, but on the good side you get very localized infestations,” said Higgins. In the areas he has inspected, the ants seem to be contained to about a city block.
Because European fire ants are commonly found in soil around the root balls of plants, it is likely these ants are being introduced to new areas through transplanting of landscaping plants. Higgins advises home owners and landscapers to check the soil for ants before planting, and be cautious about moving a plant from an infested area elsewhere. If ants are found, he recommends submerging the plant soil in water for an hour.
The nests themselves are difficult to destroy as surface pesticides are not very effective and there are multiple queens in a colony. Higgins noted that established nests could be handled with sugar and borax baits, but all residents in the affected area need to co-operate to prevent being re-invaded. An infestation is never just in one homeowner’s yard.
Higgins is advising a newly formed agency which is conducting a risk assessment on this invasive species in B.C.
“At this moment, British Columbia has just formed an inter-agency invasive species council and we’re going through the process right now of doing an official pest risk assessment for this species. That risk assessment will then be used as a foundation for how the province is going to deal with this ant,” said Higgins.
Tracy Hueppelsheuser, an entomologist for the British Columbia Ministry of Agriculture, is working as a technical advisor to the Inter-Agency Invasive Species Working Group on this issue. She said at this time there’s no indication how this ant will impact coastal BC ecosystems, but it is still a good idea for people to educate themselves on the ant.
“The primary risk of Myrmica rubra is people getting stung. Therefore, it would be in the best interest of the public to become knowledgeable about the signs of presence of Myrmica rubra and what to do if found. Loss of use of green space if the ant becomes widely established should also be of concern to the public,” said Hueppelsheuser.
ANTS ON THE MARCH: New Discoversies in BC
Hypoponera punctatissima, another invasive species Higgins identified from specimens from the Royal BC Museum, lives in building walls but is rarely noticed, as only the queens can become aggressive and sting when looking for new nests.
The specimens were found in Duncan, BC.
UBC also recently discovered samples in their collection from the 1960s, from Burnaby. Higgins identified Aphaenogaster boulderensis from a single ant, sent to himby the Spencer Museum at UBC.
This native species, found nowhere else in Canada, is located in a small area in the southern Okanagan and this find showed the range of this ant is greater than previously thought.
There is only one other type of Aphaenogaster in BC. He also discovered a species of dry wood termite in the Churn Creek protected area near Kamloops. At 52.28 degrees north it’s the highest latitude this species has been found at.
Higgins has two publications currently in press, “The effect of manipulated shading on the colony abundance of two species of ants, Formica aserva and Leptothorax muscorum, in dead wood” and “An evaluation of sampling methods for ants (Hymenoptera: Formicidae) in British Columbia, Canada.”