By Mary J Metzger
“Outside, you are never more than a foot away from an ant,” said botanist and entomologist Dr. Elizabeth Farnsworth when she spoke recently at the Nashua River Watershed Association, in a talk,”Ants in Your Plants: Interesting Insect and Plant Interactions”, co-sponsored by the Groton Garden Club made possible with a grant from the Groton Trust Fund’s Lecture Fund.
Farnsworth could qualify as a Renaissance woman, with her work as researcher, author, scientific illustrator, editor, and educator. She co-wrote and illustrated “Field Guide to Ants of New England”, and helped develop the popular online GoBotany website. She hand-built her own wooden kayak to do research for the Connecticut River Boating Guide, and currently is Senior Research Ecologist for the New England Wildflower Society in Framingham MA. In addition she is a vocalist and guitar player with the duo Easy Wind.
Pollinators are the most common associations we make with insects. “Eighty-five percent of our crops are pollinated by some kind of insect,”she said.
Ants are not big pollinators but Farnsworth outlined other interactions they have with plants and insects.
Ants have a special relationship with the endangered Karner blue butterfly. Its caterpillars produce a sticky substance that is “like a chocolate milkshake for ants.” In exchange for food, the ants protect the caterpillars.
Likewise, ants find a tasty substance on the seeds of many spring ephemeral wildflower seeds. By moving the seeds underground, they help spread the plants and ensure germination.
Ants are also soil makers.
“Harvard Forest research shows that ants make one inch of topsoil in 250 years, but what they like best is sand. So the coastal areas are abundant with ant species, some of which are just being discovered,” she said. “This makes the Sandplains Grasslands some of the most diverse habitats for all kinds of plants and insects.”
Plants have developed many ways to defend themselves from insects.
“Plants are multi-lingual,” she said. “They speak Plant and they speak Insect.”
They communicate with one another through chemical messages, either volatile gasses in the air, or through an underground fungal network. They can warn other plants to increase their chemical defenses that might give a caterpillar a “tummy-ache.”
Plants also send signals to other insects that might be useful predators. Parisitic wasps are often lured in to rid the plant of its attackers. Humans have used some insects to attack invasive plants. Galerucella beetles have been a successful introduction in the Nashua River Watershed to fight the invasive Purple Loosestrife which has taken over many wetlands.
Farnsworth takes the long view when looking at the problem of invasive insects. She pointed out that Harvard Forest research shows a centuries old bank of all kinds of seeds waiting to germinate in hemlock forests that are being decimated by the Wooly Aldegid. “Hope for Hemlocks,” by Evan Preisser of the University of Rhode Island, spells out his work of growing thousands of hemlock seedlings to find strains resistant to the Aldegid. The Massachusetts Wasp Watchers is a citizen science group that uses native non-stinging wasps to monitor for invasive beetles like the destructive Emerald Ash Borer.
Insects can also be environmental indicators. The presence of dragonflies and damselflies is a sign of good water quality. Southern ants moving north can be markers of climate warming. The State of the Plants Report issued in 2015 by the New England Wildflower Society analyzed 593 rare plant Species of Special Concern. After 15 years the plants that were losing ground were the ones that are insect pollinated. Farnsworth said the best way to support insect populations is to plant a native pollinator garden.
She also said that once you get past the “ick factor,” insects are an easy way to foster nature appreciation in children. “There are only two ants that will bite in Massachusetts. One that lives in big mounded colonies, and the other is the three-colored Red-Red-Black ant. Though if you disturb a nest, the ants may swarm over you.”