Have You Seen These Creatures?
After cottaging in Pointe au Baril since the late 1950’s, it is always surprising tocome across creatures I have never seen before. Looking down at the ground, at the trunks of pine trees and up at deciduous tree foliage, this happened 3 times last summer! Luckily, when I said aloud, “What the heck is THAT?” I was able to submit photos to staff at the Georgian Bay Biosphere (GBB) or upload pictures to iNaturalist and have these creatures identified. These first-time sightings included the North American Millipede, Bark Lice and the Redhumped Oakworm.
North American Millipede
Although I have seen other, smaller millipedes, I was surprised to spy these black and red creatures along the shaded, damp path at a friend’s cottage. In the range of 3 – 3.5 inches in length, they were hard to miss! Even though the name “millipede” means one thousand, as in number of legs, North American millipedes often have fewer than 50 pairs of legs with thde record number being 375 pairs. I estimate the few I observed had between 100 and 200 pairs. There are 2 pairs of legs attached to everybody segment except a few in the front and back ends that have only one pair. Observing them move along the rock with all their red legs working for locomotion was amazing – almost like a smooth-running wave pattern.
These long, cylindrical creatures can reach 10.2 cm (4 inches) in length and about 2.5 grams (less than an ounce) in weight. These millipedes have an exoskeleton shell covering and their segment edges can come in a range of colours. The ones I saw had reddish edges. While millipedes do not bite, they can release a noxious substance from stink glands that can irritate sensitive skin. For this reason, you should avoid picking them up. A further protective adaptation is their ability to curl up when threatened to use their hard exoskeleton ford protection.
North American millipedes can be found in Ontario and Quebec as well as in all states east of the Mississippi River and nine states to the west. These terrestrial creatures are usually found in the soil litter layer under rocks, boards, dead trees and under wet, dead leaves. The rock path I saw them on was surrounded in forest and hidden from the sun. This provided a damp area with lots of nearby leaf litter to hide in. Though they are described as “solitary and nocturnal”, I usually saw them during the day. North American millipedes are “detritivores” which means they feed on dead organic material, particularly plant detritus. They like decaying leaves, roots and wood, especially if it contains fungi and bacteria. (They very rarely eat animal tissue.) This is how they play an important role in their ecosystems, as decomposers. Keep an eye out for these interesting critters in damp, forested areas on your property!
In early August, walking down our path to the dock, a dark blotch on the trunk of one of our pine trees caught my eye. Aware that there was an abundance of Gypsy Moths this past summer and always keeping a vigilant eye out for pine sawfly larvae, I was stumped at this new sight. A closer examination revealed hundreds of small black bugs with yellow horizontal stripes, mobbing together on the tree trunk. It was a frightening sight and I immediately sent a couple photos to staff at GBB, worrying that yet another invasive species was threatening the health of our pines. I received a very quick response and was happy to read “I think those insects are tree cattle or bark lice, which do not harm trees”. Imagine my sigh of relief! I was sent a link to a blog about them and was immediately fascinated. The particular bugs I saw were nymphs or youngsters. (The adults look similar but have wings folded over their backs.) These nymphs have plump abdomens, rounded heads and long antennae. These long Bark Lice antennae were apparent upon close examination.
Now, the word “lice” brings up terrible nightmares as we think about school days and the possibility of our kids contacting the parasitic creatures in their hair. The mere name makes us want to start scratching! The name bark lice is unfortunate because they aren’t like the parasitic lice that humans and animals get. These scavengers are found on the bark of trees and feed on lichens, fungi, mold, algae, dead bark and other organic debris found on the outside of trees. Many consider bark lice to be beneficial! No chemicals or treatments are necessary, and it is suggested you enjoy the presence of these “tiny, temporary clean-up crews” if they come to visit your trees.
The article suggested a more apt name would be “bark groomers”. They are also known as “tree cattle” because they form groups or tiny “herds”. If disturbed, they will run together like a herd of cattle. Apparently, one species of bark lice will spin huge silken webs over the trunks of trees. I did not witness this and understand the species I witnessed were “aggregating bark lice”.
The species that create the heavy webbing are also harmless as are the webs. The webs can be removed if considered unsightly. While bark lice typically congregate on trunks of deciduous trees, I found them on 3 different pine trees. Finally, a beneficial insect for our trees!
The wooden walkway at my friend Tom’s cottage was being littered with oak leaf bits and caterpillar poop in mid to late August last summer. Looking up into the foliage, I spied a larva that I had never seen before. My cousin
and his wife were seeing the same larvae in their oak trees at the same time. At first, I thought it was a red headed Pine Sawfly. The biologists at iNaturalist did not identify it either. At our November GBLT Stewards’ meeting (held virtually, on Zoom) a couple other stewards said they had seen the larvae as well. One of them identified it as the
Orangehumped Mapleworm. When I searched it up for this article, I was convinced of this identification as well. However, upon further investigation, I found a report online from Ontario MNR and Natural Resources Canada entitled “Forest Health Conditions in Ontario, 2011”. Deep into the section on tree pests, I found information that distinguished the Redhumped Oakworm from the Orangehumped Mapleworm. Our oak tree pest in P au B in 2020 was the Redhumped Oakworm!
As you can see from the photograph, it has 5 black lateral lines on the middle of its back – the Orangehumped Mapleworm only has 3 of these stripes. Other than that, they are identical! They are white between the 5 black stripes and have yellow stripes that are wider than the thin, black stripes. Which end is the head you ask? The head is the orangey-red round end. The “hump” is similar colour and located near the end of the abdomen. They may grow to a
length of 4.5cm (1.75 inches) which was about the size of the larger caterpillars we observed. While they prefer to feed on oak (that’s where we saw them), they will also feed on a variety of other hardwood trees like beech and chestnut. These late season defoliators can cause extensive leaf loss but because this occurs late in the season, it rarely affects tree health. (Technically, if the tree was affected by another defoliator earlier in the season and also suffered from adverse conditions like lack of rain, tree health could be threatened.) However, this usually is not the case. So, if you observed these creatures on your oak trees last summer, the trees should be fine in 2021.
Populations of Redhumped Oakworms are usually controlled by natural enemies. Some of these are parasitoids (other small insects that develop within or attached to the Oakworm and eventually kill it), diseases and predators like birds. Eggs are laid by adult females in June or July in groups of about 50 on the underside of leaves. The eggs hatch in about 10 days
and the caterpillars initially feed in colonies. Mature caterpillars fall to the ground later in September and pupate between rolled leaves in the leaf litter. Adult moths emerge in June and there is only one generation per year. Adult moths are difficult to identify. They are grey-brown with a deeper brown area at the wing edges and white sides jut into the middle of the wing. If you can’t identify the moth, you will certainly be able to identify the caterpillar or larval stage! Keep an eye on your oak tree leaves in mid to late August to see if the Redhumped Oakworm is feeding on them.