Insects That Mimic Stinging Wasps: A Look at Synanthedon acerni

In a previous post, I wrote about syrphid flies that mimic bees and wasps. But are there other insects with this mimicry superpower? The answer is yes. Other types of flies, beetles, and moths all have species that mimic stinging insects. The moth Superfamily Cossoidea (Carpenter and Clearwing Moths) is notable for the many species that mimic stinging wasps.

Synanthedon acerni (Family Sesiidae, Subfamily Sesiinae, Tribe Synanthedonini) is one such very wasp-like moth. Its wasp-like appearance allows it to be active during the day while it visits flowers, feeding on nectar.

Life history

The larvae of Synanthedon acerni are not quite as benign. Known as the maple callus borer moth, its larvae bore into the trunks of maple (Acer spp.) trees. Eggs are laid near wounds in the bark. Entry into the tree is through these wounds on the tree’s trunk. The larvae bore into the bark and then into the cambium, where they feed on the inner bark and sapwood. Feeding takes place during the summer within galleries. In the winter, they hibernate in the galleries and resume feeding in the spring.

At maturity, the larva constructs an oblong cocoon of wood fragments, frass, and silk within the gallery, close to the surface, covered by a thin escape window. When ready to emerge, the pupa cuts open the cocoon and the escape window. The fully formed Synanthedon acerni moth then exits the pupa, which is left partially stuck in the gallery.

The same tree may be used year after year, weakening it and eventually leading to its demise. A callus will form on the trunk after repeated infestations.

Halysidota tessellaris (Banded Tussock Moth): Identification and Life Cycle

In an earlier post, I wrote about Lophocampa maculata, a moth in the Arctiinae, distinguished by its fuzzy black and yellow larvae. These larvae later metamorphose into beautiful adult moths with a contrasting pattern of alternating bands of warm, muted golden-orange and darker brown markings with a reddish-orange tinge. In this post, I write about Halysidota tessellaris, the banded tussock moth, another moth in the Arctiinae.

*Halysidota tessellaris* caterpillar feeding on a crabapple leaf in late summer.

Identification

Like Lophocampa maculata, the larvae of Halysidota tessellaris are also fuzzy, but they are usually gray to dingy brown with long white and long black tassels. The adult moth, while similar in size to Lophocampa maculata, has translucent yellow forewings marked with slightly darker bands and irregularly shaped block-like cells that form a tessellated pattern. Also, there are two parallel blue stripes on the fuzzy thorax.

Life cycle

Across its range, larvae of Halysidota tessellaris feed on many species of hardwood tree leaves. Among these are box elder (Acer negundo), sweet birch (Betula lenta), ash (Fraxinus spp.), oaks (Quercus spp.), and many others. Adult moths take nectar and are pollinators of milkweeds (Frost, S. W. (1965) Insects and Pollinia. Ecology, 46. 556-558, paywall).

*Halysidota tessellaris*, a worn specimen, but the blue lines are prominent.

Similar species

Adults of the related Halysidota harrisii (sycamore tussock moth) are similar in appearance to Halysidota tessellaris. Where the ranges of Halysidota tessellaris and Halysidota harrisii overlap, genital dissection is necessary to determine the species. Halysidota harrisii larvae, which may be solid white, yellow, orange, or gray, feed exclusively on sycamore (Platanus occidentalis) leaves. The ranges of sycamore and the moth coincide closely.

Discovering the Yellow-Spotted Tussock Moth Caterpillar

**A *Lophocampa maculata* caterpillar that has been feeding on a balsam poplar leaf on a sunny afternoon in September.**

When fall is coming, many fuzzy caterpillars start to show up in the grass and on low trees. A familiar one is the woolly bear caterpillar, which is alleged to foretell the severity of the coming winter. Longer black bands are said to mean a colder winter, while longer orange bands mean a milder winter.

The yellow-spotted tussock moth (Lophocampa maculata) is another fuzzy caterpillar often seen in the fall. It is also a relative of the woolly bear in the Family Erebidae, Subfamily Arctiinae (tiger moths and lichen moths). No word on its meteorological abilities.

Caterpillar decription

The younger Lophocampa maculata caterpillars are orange and without the black ends. When fully grown, it develops a yellow to orange central band, capped by shorter back bands at each end. Some will also have black dots in the yellow band. All the hairs of this fuzzy caterpillar are in clusters called fascicles. The shorter ones that cover most of the body remind me of splayed paint brushes. Tufts of stiff white hairs (“lashes”) poke out from the shorter, denser body hairs of the head and posterior black bands.

Caterpillar variations

Below are some variations of the caterpillar’s coloring on larvae I found just a few miles away from my home. All have spots down the back, and two do not have black anteriors or posteriors. The one on the left is feeding on beaked hazel, the middle one is on tag alder, and the one on the right is feeding on shining willow.

Adult moth description

Adult Lophocampa maculata moths are distinguished by a contrasting pattern of alternating bands of warm, muted golden-orange and darker brown markings with a reddish-orange tinge

Life cycle

After hatching from eggs laid in summer, the Lophocampa maculata caterpillar feeds and grows. Preferred food plants are deciduous tree leaves such as aspen, willow, birch, oak, maple, and apple.

When cold weather seems inevitable, the caterpillar goes into pupation to wait out the winter. The pupa is enclosed in a silken cocoon attached to plant leaves. In my area, between late June and early July, the moths will hatch from their cocoons to fly in search of a mate, beginning the process again.

Adult Lophocampa maculata moth — **This yellow-spotted tussock moth (*Lophocampa maculata*) came to my light this summer on June 29th.**

Similar species

Lophocampa caryae adults are similar to Lophocampa maculata, but the forewing is yellow with brown shading and lacks the yellow band on the terminal ends of the forewing. Their larvae are white with black markings and long hairs. It is found mainly in the northeast. Like Lophocampa maculata, the larvae are polyphagous and feed on leaves of hickory, ash, oak, maple, elm, and other woody plants and vines.

Macrochilo Bivittata: A Rare Wetland Moth

Macrochilo bivittata is one of those moths I look forward to seeing every year. It isn’t a showy species, just a small triangular-shaped moth with four dark stripes against a buff to brown background, some prominent wing venation, and two pairs of dots. It is in the Herminiinae or litter moths, named because the larvae of many species feed on fallen or dead leaves and fallen fruit.

The reason I get excited about seeing it again is that where I live is one of the few known places in North America where it occurs. Across its range, Macrochilo bivittata is uncommon to rare. Minnesota and Wisconsin appear to have the largest number of observations. The rarity of Macrochilo bivittata may be a lack of verified observations and not rarity based on specialized habits or food requirements, loss of habitat, or replacement by a non-native species. More searches in appropriate habitat could help to resolve this.

A few Macrochilo bivittata moths come to my moth light every year in July. But it is in a nearby old marsh grass hayfield, now reverting to sedge meadow-shrub carr wetland, where I see many more. As I walk through the tall grasses, sedges, and willow shrubs, dozens of these little moths fly ahead of me to escape the disturbance.

**The sedge meadow-shrub carr wetland where *Macrochilo bivittata* lives. Except for a few patches of canary grass, most of the plant species here are native.**

The food preferences of Macrochilo bivittata are not known. It is thought their larvae feed on leaf litter like other members of the Herminiinae. There is certainly an abundance of leaf litter out there under the grasses and willows in the old hayfield. Macrochilo bivittata seems to be doing very well with that.