Chestnut casebearer moth

Chestnut blight from East Asia devastated more than just the American chestnut

The American chestnut casebearer moth relied on the native American chestnut (Castanea dentata) for survival. This hardwood tree was the sole host plant for its larvae, ultimately leading to the highly specialized moth species’ downfall.

Once one of the most important trees in the eastern United States, the American chestnut faced devastation starting in 1904. That year, chestnut blight (Chryphonectria parasitica), an Asian fungal pathogen that parasitizes chestnuts, was accidentally introduced to America via some saplings of the Chinese ornamental chestnut.

Within a few decades, the populations of the susceptible American chestnut collapsed. Consequently, the chestnut casebearer moth also suffered, losing its host plants.

The spread of the fungal disease was particularly rapid, as the spores were disseminated by wind, rain, insects, and birds. By 1950, chestnut blight had almost entirely eradicated the American chestnut, leaving it rare today.

The American chestnut once played a crucial role in the flora and fauna of North America. Its foliage and nuts were a fundamental food source for many animal species, including the passenger pigeon, which went extinct in 1914.

Another factor that may have contributed to the extinction of the chestnut casebearer moth is that the insects were parasitized by at least two wasp species. The wasps used the moth as a host organism.

Chestnut casebearer moth – Fact sheet

Alternative name	chestnut casebearer, chestnut case-bearer moth, chestnut case-bearer, American coleophorid moth
Scientific name	Coleophora leucochrysella
Original range	Indiana, Pennsylvania, Virginia (USA)
Date of extinction	between 1904 and 1950 – rediscovered in 2020
Causes of extinction	fungus introduced from Asia, loss of the host plant

On the lifestyle of the chestnut casebearer moth

The American entomologist James Brackenridge Clemens, who specialized in butterflies and moths (Lepidoptera), scientifically described the chestnut casebearer moth in 1863. Coleophora leucochrysella belongs to the family of casebearing moths or leaf miners (Coleophoridae).

The larvae of the chestnut casebearer moth, which had a wingspan of around 1.5 centimeters, lived in the leaves of the American chestnut and fed on them. Older larvae used parts of the tree to spin a protective case around their bodies, about one centimeter long.

The chestnut casebearer moth was once native to the states of Virginia, Pennsylvania, and Indiana, all located in the eastern USA. Since the moth species was known only from these areas, and today there are very few American chestnut trees producing viable nuts, with no larvae of the moth species found, it was assumed to be extinct.

Chestnut casebearer moth not extinct after all

In early June 2020, lepidopterist Steven Whitebread photographed a larval case on an American chestnut in Northfield, Massachusetts, and shared his discovery on the iNaturalist platform. Nearly two weeks later, he added images of the emerged moth. Whitebread later suggested that the images might depict the chestnut casebearer moth, previously thought to be extinct. Regarding his observations, he noted:

“They were mostly on fairly decent-sized trees, but also on saplings. Probably none of the trees were fully resistant. I was too late to find feeding larvae and most of the records I have are of feeding windows, some found at the top of the trees using binoculars, but a lot also at head height. (…) I was able to find a couple of cases affixed for pupation on the undersides of leaves. (…) Feeding windows soon disintegrate and it was difficult to find any just 2 weeks later.”

Steven Whitebread on iNaturlist in January 2022

The naturalist and author Charley Eisemann, who has a special interest in small insect larvae that live inside plant leaves and feed on their tissue – so-called leaf miners, subsequently sent specimens found in Massachusetts to Jean-François Landry, the North American expert on casebearer moths (Coleophoridae). Landry ultimately confirmed the identification of the photographed animals as Coleophora leucochrysella.

The rediscovery of the chestnut casebearer moth, more than 70 years after its last sighting, highlights the resilience and adaptability of species to extreme habitat changes. This renewed discovery also underscores the potential of citizen science platforms like iNaturalist, which allow for the sharing of photos and documentation of nature observations. The International Union for Conservation of Nature (IUCN) still lists the chestnut casebearer moth as extinct.