22/12/2025
The Hidden Enemies of Densho
Insects That Damage Japanese Scrolls — Identification, Prevention, and Eradication
Introduction — When Time Is Not the Enemy
When an old densho (伝書) or makimono (巻物) shows damage, the instinct is often to blame age. Yet age alone does not eat paper, hollow silk, or bore perfect circular holes through centuries-old manuscripts.
The true enemies of Japanese scrolls are insects.
For more than a thousand years, Japan’s written culture—martial, religious, artistic, and medical—has been threatened not by fire or war alone, but by small, persistent creatures drawn to the very materials that define traditional manuscripts: washi paper, rice paste, animal glue, silk, and wood.
Understanding these insects is not optional for anyone entrusted with old scrolls. It is a fundamental responsibility.
I. The Primary Scroll-Damaging Insects of Japan
1. Silverfish
Japanese: 紙魚（シミ, shimi)
Order: Zygentoma
Silverfish are the most historically documented manuscript pest in Japan. Edo-period texts explicitly describe their damage under the term 虫損 (mushison).
What they eat:
Rice-starch paste (糊)
Paper sizing
Ink binders
Surface coatings on washi
Damage pattern:
Irregular surface grazing
Softened, thinned paper
Uneven holes rather than clean perforations
Keynote:
Silverfish are not eating “paper” itself—they are consuming the nutrients that hold the paper together.
2. Booklice
Japanese: チャタテムシ（茶立虫）
Order: Psocodea
Often confused with silverfish, booklice are a secondary but dangerous indicator species.
What they eat:
Mold
Starch residues
Organic dust
Damage pattern:
Weakening of fibers
Accelerated deterioration rather than direct holes
What their presence means:
If you see booklice, you have a humidity problem, not merely an insect problem.
3. Beetle Larvae (So-called “Bookworms”)
Japanese: シバンムシ類・ヒラタキクイムシ類
Common species include:
タバコシバンムシ (Lasioderma serricorne)
ジンサンシバンムシ (Stegobium paniceum)
ヒラタキクイムシ類 (powderpost beetles, Japan-relevant)
What they eat:
Paper
Paste layers
Silk mountings
Wooden storage boxes
Damage pattern:
Clean, round holes
Tunnels passing through multiple scroll layers
Powdery frass inside boxes
⚠️ This is the most structurally destructive insect threat to densho.
4. Termites
Japanese: 白蟻（シロアリ, shiroari）
Primary targets:
Wooden scroll boxes
Shelving
Storage rooms
Damage pattern:
Hollowed boxes
Collapsing storage
Edge destruction of scrolls stored within
Once termites reach paper, the damage is often catastrophic and irreversible.
5. Clothes Moths
Japanese: 衣蛾（コロモガ）
Primary target:
Silk mountings (表具裂)
Damage pattern:
Edge loss
Detached backing layers
Structural instability of the scroll
6. Cockroaches
Japanese: ゴキブリ
Damage pattern:
Irregular chewing
Smearing
F***l staining
Less common, but extremely damaging when present.
II. Recognizing Insect Damage at a Glance
Damage Type Likely Culprit
Surface grazing Silverfish
Clean round holes Beetle larvae
Hollowed edges / boxes Termites
Powdery debris Active infestation
Silk loss Moths
III. Traditional Japanese Methods of Scroll Protection
Japan developed effective insect deterrence long before modern chemistry.
1. Kiribako (桐箱) - What makes kiribako special - Paulownia wood (桐, kiri) has properties that directly counter insect damage:
Natural insect resistance
Kiri contains compounds insects dislike
Not toxic, but repellent
Especially effective against silverfish and beetles
Humidity buffering
Kiri absorbs and releases moisture slowly
Prevents mold → prevents booklice
Stabilizes the micro-environment inside the box
Thermal stability
Insulates against rapid temperature change
Reduces condensation risk
Light weight + tight grain
Boxes seal well without crushing contents
Ideal for rolled materials
This is why every serious Japanese collection, from temples to daimyo archives, used kiribako.
2. Camphor Wood Boxes
樟の箱 (kusunoki no hako)
Naturally repels insects without harming paper.
3. Camphor and Clove
樟脳 (shōnō) placed in storage boxes.
4. Seasonal Airing
曝書 (bakusho)
Scrolls were periodically unrolled and aired to prevent moisture accumulation.
IV. Modern Best Practices for Caring for Densho & Makimono
Environmental Control
Humidity: 45–55%
Stable temperature
Good air circulation
Storage
Acid-free wrapping
Inert archival boxes
Separation of infected items
Handling
Clean hands
Minimal unrolling
No food or drink nearby
V. Removing and Killing Insects Safely
⚠️ What NOT to Do
No sprays
No insecticides
No fumigation chemicals
These will permanently damage paper and ink.
✅ Safe and Accepted Methods
1. Freezing
Seal scroll in airtight bag
Freeze at −20°C (−4°F) for 7–10 days
Slowly acclimate back to room temperature
This kills all life stages: eggs, larvae, adults.
2. Anoxic (Oxygen-Free) Treatment
Nitrogen or argon environments
Museum standard
Extremely effective and non-invasive
3. Isolation and Monitoring
Remove infected items immediately
Monitor surrounding materials
Never reintroduce without treatment
VI. Final Word — Custodianship, Not Ownership
To hold a densho is not to own it—it is to temporarily guard a lineage of knowledge.
Insects have no malice. They simply follow biology. The responsibility lies with us to understand their behavior and prevent the slow, silent erasure of history.
For Yakushin Publications, preservation is not an afterthought. It is the foundation upon which translation, scholarship, and transmission stand.
