What Kind of Moths Are Antheraea yamamai and Caligula japonica?
Antheraea yamamai (Antheraea yamamai) is a moth native to Japan in the family Saturniidae, called the Japanese Giant Silkmoth in English. With a wingspan of 13–15 cm, it is one of Japan's largest moths, and its beautiful pale-green wings adorned with translucent "eyespots" (ocelli) captivate not only insect enthusiasts but many others as well.
Caligula japonica (Caligula japonica) is likewise a large moth in the family Saturniidae with a wingspan of 12–13 cm. Unlike Antheraea yamamai, it feeds on a variety of plants including camphor tree and chestnut leaves.
Basic Information
| Item | Antheraea yamamai | Caligula japonica |
|---|
| Scientific Name | Antheraea yamamai | Caligula japonica |
| English Name | Japanese Giant Silkmoth | Japanese Oak Silkmoth |
| Wingspan | 13–15 cm | 12–13 cm |
| Primary Larval Food Plants | Japanese oak, Kunugi oak, Chestnut | Camphor tree, Chestnut, Wisteria, and various others |
| Egg Laying Season | Autumn (September–October) | Autumn (October–November) |
| Larval Activity Period | May–August | April–July |
| Adult Emergence Period | August–October | September–October |
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Appeal and Precautions for Rearing
Appeal
Large Larvae and Adults: Final-instar larvae can reach 8–10 cm in body length, producing impressive hairy caterpillars (though non-venomous). The beauty of adult moths is incomparable to other species.
Univoltine Lifecycle: A single generation per year (eggs in winter → hatching in spring → pupation in summer → adults in autumn), allowing for planned rearing.
Silk from Cocoons: The cocoons of Antheraea yamamai are known as "tussah silk" (天蚕糸, heavenly silkworm silk), a lustrous pale-green silk thread highly valued as a traditional crafting material.
Precautions
Adults Have No Mouth: Adults of the family Saturniidae lack functional mouthparts, so they cannot eat. Adult lifespan is only 1–2 weeks, with mating and egg-laying as their sole purpose.
Continuous Food Plant Supply is Essential: Larvae feed exclusively on fresh leaves, so you must ensure a steady supply of food plants throughout the rearing period (May–August).
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Egg Acquisition and Hatching
How to Obtain Eggs
- Collection: Capture wild adult Antheraea yamamai in autumn (September–October) from woodland edges and allow them to mate and lay eggs
- Purchase or Transfer: Obtain eggs from insect events or online retailers (no legal restrictions)
- Overwintering Eggs: Eggs are cold-hardy and can be stored in a refrigerator (around 5°C) until spring
Hatching Management
- Optimal Hatching Temperature: 15–25°C (natural hatching as temperatures rise in spring is ideal)
- Eggs darken in color just before hatching
- Newly hatched larvae are extremely small (3–5 mm) but actively seek food plants
- Provide fresh young leaves or tender shoots of the food plant (such as oak) within 24 hours of hatching
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Food Plant Preparation
Food Plants for Antheraea yamamai
Primary food plants: Japanese oak, Kunugi oak, Chestnut, and Oak species
- Japanese oak and Kunugi oak are abundant in mixed deciduous woodlands and are the easiest to obtain
- Young leaves are most readily accepted (tender new shoots are essential, especially immediately after hatching)
- Cut branches can be placed in a vase with water or wrapped in damp paper towels for storage
Food Plants for Caligula japonica
Primary food plants: Camphor tree, Chestnut, Wisteria, Willow, and Oak species (polyphagous)
Caligula japonica is more polyphagous; using camphor tree (an evergreen that retains leaves year-round) makes securing food plants easier.
Food Plant Freshness Management
- Cut branches wilt within 1–2 days, so replace with fresh foliage daily or every two days
- Avoid leaves from trees treated with pesticides (especially public parks and street trees)
- Growing potted Kunugi or Japanese oak at home ensures a stable food supply
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Rearing Container and Management
Container Selection
| Instar | Recommended Container | Size |
|---|
| 1st–2nd (body length 3–20 mm) | Small plastic container | W20×D15×H20 cm |
| 3rd–4th (body length 30–60 mm) | Medium plastic container | W30×D20×H30 cm |
| 5th final (body length 80–100 mm) | Large plastic container or observation cage | W40×D30×H40 cm or larger |
Ventilation: Larvae are highly sensitive to moisture buildup and fungal issues, so use containers with large ventilation holes and line the lid with mesh to ensure adequate airflow.
Environmental Settings
- Temperature: 20–28°C (high heat and humidity increase mortality from moisture stress)
- Humidity: 60–70% (avoid excessive moisture and excessive dryness)
- Substrate: Not needed (lean branches against the container or insert them upright)
- Molting Precautions: Before molting, larvae stop feeding and become motionless. Avoid changing food or cleaning the container during this period
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Molting and Instar Management
Antheraea yamamai larvae undergo five molts (reaching five instars) before pupation.
| Instar | Duration (approximate) | Characteristics |
|---|
| 1st | 1 week | Black to brown, small |
| 2nd | 1 week | Color becomes lighter |
| 3rd | 10–14 days | Green color begins to appear |
| 4th | 14–21 days | Bright green |
| 5th (Final) | 3–4 weeks | Largest (8–10 cm), preparing for pupation |
How to Identify Molting: Before a molt, the head appears enlarged and the body seems shrunken. Never touch a larva during molting, as it may damage the body.
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Pupation and Winter Dormancy
Pupation Preparation: When a final-instar larva begins spinning silk, pupation is beginning. Place a stick or branch in the container so the larva can spin its cocoon around it.
Cocoon Management
- Keep the completed cocoon in the container at room temperature in a cool location
- Antheraea yamamai overwinters as a pupa (pupal diapause)
- Adults emerge the following year during August–October (approximately 10–11 months later)
- Avoid overly dry locations; maintain moderate humidity around 60%
Emergence Observation
- The cocoon begins to move just before emergence
- Emergence typically occurs early morning to mid-morning
- Once emerged, the adult spreads and dries its wings; do not handle (wings may become deformed)
- The adult clings to the mesh lid of the container to expand its wings
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Conclusion: Experiencing the Mystery of Japan's Mountain Moths
Rearing Antheraea yamamai and Caligula japonica is a relatively straightforward insect-rearing project, provided you can secure food plants and manage ventilation. Watching tiny newly-hatched larvae gradually grow, spin large cocoons, and emerge the following year as beautiful adults is one of the most moving experiences in insect keeping.
If you have access to parks or woodlands with oak or chestnut trees nearby, consider collecting wild adults during the autumn egg-laying season and attempting to rear the resulting larvae the following year.
