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Entomology (Study of Bugs)/Cocoon debris found on artwork

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Question
Cocoon detail
Cocoon detail  

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Dear Jack,

I'm an art conservator who specializes in works of art on paper. Recently, a client brought me a large gouache painting that was covered in over 30 discrete, fuzzy white accretions that I believe to be old cocoons. This painting had been framed under glass for over 20 years and came from an auction house in Massachusetts. Previous ownership/storage conditions are unknown.   

The accretions measured between 1/8" - 5/8" and they were composed of masses of semi-opaque strands of sticky white silk. I was able to clean them off of the painting's surface using a soft bristled brush-- they stuck to the hairs of the brush and were easily lifted off of the painting. They did leave a stain on the paint surface. I did not find any insect remains on the painting or in the frame.  

Do you have any idea what type of insect may have left this debris? I'd like to have an idea about the chemical composition of the staining so that I can develop a cleaning method.

Thank you for your time,
Amy

Answer
Amy,

These may be the cocoons of the casemaking clothes moth (see http://www.livingwithbugs.com/clothes_moth.html for pictures). The larvae normally feed on protein-based materials like wool or silk so they may have fed on the paper's sizing (gelatin). The stains are probably from inside the cocoon so would also be protein, similar to a blood stain.

Post a follow up if you have questions.

Jack DeAngelis

Entomology (Study of Bugs)

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Jack DeAngelis

Expertise

I can answer questions in any area of entomology (study of insects, spiders, mites, ticks, and other terrestrial arthropods). Contact me about home and garden insects, insects that bite and sting, and insects that damage homes such as carpenter ants and termites.

Experience

20 years as university extension entomologist, now retired; currently publish a website about home and garden insects.

Publications
see www.livingwithbugs.com/resume.html

Education/Credentials
Ph.D. in Entomology

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