They're lean, mean, leaf-eating machines, and they could be coming to a tree near you.
They're forest tent caterpillars, a distinctive black caterpillar with a telltale blue stripe down the length of its back, and they're currently busy munching and defoliating trees in various areas of the city.
"They just clean a path of devastation wherever they go," Martha Barwinsky, the city's forester, said on Monday after plucking one of the insects from a tree for a quick photo session.
'They just clean a path of devastation wherever they go'
"If it's one year of defoliation, it puts stress on the tree. The tree will re-leaf, but that comes from its reserves.
"If it happens several years in a row, then it becomes a big problem for the tree."
Barwinsky said the caterpillars come in cycles about once in 12 to 15 years, and it has been 13 years since the last infestation.
That was in 2001, with the east side of the city the hardest hit. There were also pockets of the caterpillars throughout the city in 2000 and 2002.
The caterpillars could be seen on trees massing together into large undulating patches on the trunk. They would then move to the rest of the tree and strip it of leaves before moving on to other trees. When they become adults, they are a brown or tan -coloured moth with a wingspan about three or four centimetres wide.
Winnipeggers were quoted in the Free Press in 2001 as saying if you stood still too long, the caterpillars would begin crawling up your legs. Others said they were forced to use brooms and shovels to get them off their porches and steps.
Barwinsky said this year it is the east side of the city that appears to be the prime dining spot for the caterpillars, including Transcona, Sage Creek and Canterbury Park, but once again there are pockets being reported throughout the city, including the downtown and Weston.
Barwinsky said she doesn't know how far along in the up to three-year infestation cycle we are in.
"We have small numbers through the city now, but we are expecting to see greater numbers next year. Right now we think this is in the early stages."
She said the infestation ends when the population crashes -- for reasons not really known -- and then it takes more than a decade for them to rise in numbers again.
Barwinsky said the city is not going to spray the trees at this time because there aren't enough of the caterpillars, but if homeowners want to they can use the biological agent BTK.
"You have to make sure you apply it to the trees on the leaves, not the bugs. They have to ingest it for it to work."