- Do you have questions about birds, bugs, bees, butterflies or other wildlife? Send your questions to Wild Things and we will try to find the answers.
Although people spot most moths fluttering about their porch lights at night, the eight-spotted forester moth (Alypia octomaculata) is unusual: It ventures out during the day. Because it is also colorful, people often mistake it for a butterfly, but you can tell by the way it folds its wings it is a moth. Moths and butterflies have many similarities, but moths evolved long before butterflies. Scientists have found moth fossils that are 190 million years old. Butterflies did not arrive on the scene until 60 million years ago.
Not surprisingly, this moth has eight spots: two cream-colored ones on each forewing and two white ones on each hindwing. It also has cream-colored shoulder patches. The rest of its body is black, except for bright orange hairs at the top of its front and middle legs. The orange hairs almost look like full pollen baskets, which you see on some bees, but moths do not collect pollen. They sip nectar with their strawlike proboscis for energy. They consume the vast majority of their food as a caterpillar, and now live only to mate and lay eggs to repopulate the species.
You may be surprised to learn that the eight-spotted forester moth is native to Canada! It has just extended its range – now it can be found as far south as Mexico.
An adult eight-spotted forester moth emerges from a pupa (chrysalis or cocoon) in the spring. The adult feeds on the nectar of flowers, pollinating them as it unintentionally carries pollen from flower to flower. In late May or June, it lays eggs on wild or domestic grape plants, pepper vines or woodbine/Virginia creeper (Parthenocissus quinquefolia). When the eggs hatch, the caterpillars attach themselves to the underside of leaves of the host plant, and munch away.
If the caterpillar of this moth feels threatened, it vomits an orange-tinted liquid. If this action is not enough to repel a predator, the caterpillar falls off its leaf, attached only by a silk-like bungee cord excreted from its mouth.
The caterpillars grow through five stages, shedding their skin each time it becomes too tight.
In the fall, the mature caterpillars burrow into rotten wood, pulpy soil or even trash. Here they spin a soft-walled pupa and enter a hibernating stage called diapause. But they don’t necessarily metamorphose into moths the following spring: These moths can stay in the cocoon stages for up to four years. In one study, an entomologist raised 80 eight-spotted forester caterpillars, which over the course of a season developed into 50 pupae. The following spring, in 1978, nine moths emerged. In 1979, 25 more moths emerged. In 1980, four moths emerged, and in 1981, one last moth emerged. Scientists do not know what triggers this moth to emerge from its pupa.
Although we do not see this moth that much today, there was a time when this moth was plentiful. In 1882, The Canadian Entomologist published this description:
Last June I was in Boston, from the 14th to the 30th, and during this time Alypia octomaculata was in season and very abundant. Had I chosen to carry a net in the public gardens and uptown streets, I suppose I could have taken a couple of hundred specimens, provided I wasn’t “run in” as a lunatic. As it was, I contented myself with carrying a supply of pill boxes and succeeded in taking about thirty-five specimens. During two days I was visiting a friend about seven miles from the city; … in those streets in which there were small plots of grass in front of the houses, they were very common. The spot where I took the most of those I captured was a plot of grass about ten feet by seven, in which there was a Syringa [lilac] between two Deutzias [hydrangeas], both species of shrub being in blossom.
This moth was considered a pest, and people in the late 1800s and early 1900s used control methods that would not be considered today. One was a spray called London purple, an insecticide that contained arsenic. London purple is highly toxic if inhaled, absorbed by the skin or ingested. According to the Journal of Economic Entomology, London purple “was much used in New York City about 1890, being recommended by E.B. Southwick, who had charge of the trees and shrubs in Central Park.” It was best “applied when caterpillars are small.”
Another common insecticide used to control these moths was arsenate of lead – that is, it contains both lead and arsenic. In 1916, in the yard of a man in New Haven, Connecticut, “thousands of caterpillars, mostly fully grown, were found feeding on nearly all kinds of foliage in the yard, but were especially abundant upon the grape and Virginia creeper. These proved to be the larvae of the Eight-Spotted Forester.” To combat this infestation, the homeowner sprayed with arsenate of lead, “which proved to be most effective. It was difficult to find any living larvae.”
Today we know that exposure to arsenate of lead can cause neurological damage, birth defects and even cancers. Arsenate of lead persists in soil, leading to the contamination of land. It also kills birds and water organisms. Residues remain in food even after washing. Lead arsenate is banned in the United States – but it wasn’t until 1988.
Today, most people are happy to spot just one of these small, one-and-a-half-inch moths. Being able to see hundreds as in the past seems unfathomable. These moths are most often found in open areas with woodland borders. Flowers, which the adults nectar on, grow in open areas. Grapevines and Virginia creeper, which the hungry caterpillars devour, grow in woodland borders. Peer into a neighbor’s grape arbors for the best chance to spy this colorful, day-flying moth or its caterpillars (but it’s been known to happen on Somerville’s Community Path too).
Have you taken photos of our urban wild things? Send your images to Cambridge Day, and we may use them as part of a future feature. Include the photographer’s name and the general location where the photo was taken.
Jeanine Farley is an educational writer who has lived in the Boston area for more than 30 years. She enjoys taking photos of our urban wild things.
A stronger
Please consider making a financial contribution to maintain, expand and improve Cambridge Day.
We are now a 501(c)3 nonprofit and all donations are tax deductible.
Please consider a recurring contribution.