The domestic silkmoth (Bombyx mori) is an insect in the family Bombycidae (the moth family) and genus Bombyx (the true or mulberry silkmoths) whose caterpillar or larvae known as silkworm with their common variation being Zebra, White Seductress, and Tiger.
Silkworm has many uses, including sericulture or silk farming, and as a feeder insect to various insectivorous pets and animals like bearded dragons, geckos, turtle, birds, frogs, and others.
Also, in some places, human beings, especially in Korea, Japan, and China, eat their pupae. In China, people love this insect’s roasted or fried silkworms or their pupas.
The mulberry and non-mulberry silkworms
Some silkworm types do not belong to the genus Bombyx (non-mulberry silkworms such as Tasar, Eri, Muga, Anaphe, Fagara, Coan, Mussel, and spider silkmoths. However, we will be focusing on the mulberry or domestic silkmoth.
Silkmoth cocoon colors
Naturally, the colors of the cocoons vary. They can be white, yellow, salmon, straw, pink, or green. They get this pigment from mulberry leaves.
Where do silkmoths live – habitat
Due to many years of domestication and breeding, most domestic silkmoths depend on human beings for survival, as most of them cannot fly. Therefore, they live in human-modified habitats.
However, while in the wild, species such as Bombyx mandarina that fly, being selective feeders, they will live on a mulberry tree.
The primary disease that may affect these worms includes Beauveria bassiana (fungal), Flacherie (caused by a virus or poisonous food), Pébrine (caused by a parasitic microsporidian), Grasserie, and Muscardine (caused by a collection of fungus).
Silkmoth life cycle
The entire lifespan of a silkmoth is about 6-8 weeks. However, weather conditions may influence this lifespan. For instance, in areas with seasonal change, female moth lays eggs on as summer ends, and they do not hatch until spring. However, in warmer regions, breeding is ongoing.
Egg stage 7-14 days to hatch
Adult female silk month lays about 300-500 eggs on mulberry leaves together with a gelatinous secretion to make them stick onto these leaves.
The eggs hatch after 7-14 days if there are conducive under temperatures of 75 to 85 °F (75 to 85 °F). In cold conditions, they can last for long without hatching into larvae.
Silkworm larvae stage 24- 30 days
The newly hatch larvae, silkworms, grubs or caterpillars are about 1/8 inch or 2-3mm in size, and they can grow up to 3 inches by the end of this larvae stage. Their body has tiny black hairs, and they have a big appetite for mulberry leaves.
These grubs molt four times, each after 5-6 days. The in-between molting stage is known as instar, and after the first instar, they grow a caudal (posterior) horn.
Immediately before they molt, their head darkens a bit. After shedding their old skin, a white-colored, hairless bigger larva emerges with bigger soft skin larvae with a horn.
Pupae stage 12-15 days
After their fourth molt, they will begin preparing for pupation. Their body turns yellowish, and their skin tightens. Afterward, they will find a twig and spin their cocoon that can be yellow or white.
During the spinning exercise of their silk cocoon, their salivary glands secrets fibroin protein filament, which solidifies upon being exposed to air. They also secrete sericin gum to cement their silk filament, it takes 2-3 days, and they can spin as long as 900m of silk filament.
While in their cocoon, the silk moths molt for their final time to provide them with an extra protective layer.
When the pupae or chrysalis are about to undergo metamorphosis to adults, release an enzyme that creates a hole for their escape from the cocoon.
Adult stage: 5-10 days
After opening their cocoon, an adult moth emerges. They don’t eat (unless fed by their caretaker) as they have a reduced mouth. Furthermore, these moths have a wingspan of about 3–5 cm but don’t fly (however, a few do fly), and they have a hairy body.
They immediately being to look for a mating partner. The females, who are 2-3 times bigger, release a sex pheromone known as bombykol that makes the males perform a mating ritual, the flutter dance where they vibrate their wings with excitement.
Mating takes several hours. Afterward, female lays eggs and die. The males have a longer lifespan but don’t leave for more than 10-11 days.
What eats silkworm?
Besides its use in silk farming, silkworms are a staple feeder insect. Some of the pets and animals that feed on these larvae include:
- Reptiles such as turtles, snakes, lizards like bearded dragons,
- Amphibians like toads, salamanders, and frogs
- Invertebrates – Spiders
- Fish – For instance, in koi fish, they improve their slime coat, making this fish protect themselves better from parasitic or bacterial infections.
- Birds – Captive and domestic birds such as finches, parrots, quails,
- Vertebrates such as rats, crows, squirrels, wild birds, which eat both the larvae and pupas.
- Invertebrates, such as ants, mosquitos, wasps, straw mites, beetles, and so forth, eat silkmoth pupae and larvae.
- They are more appealing and taste better when compared to most of the other feeder insects
- TheymMove slowly. Therefore, they cannot jump, leap or escape like locusts, crickets, and grasshoppers.
- They don’t bite since they have no sharp legs or jaws.
- They are ideal for picky pets that refuse to eat other foods.
- Their body is soft making eating and digestion very easy
- They are easy to raise. They don’t need much of investments or accessories.
- They live longer
- They are easy to care for
- Bigger in size, hence you need fever,
- Are odorless
- Very profitable joins the ranks of the honeybee.
- Hatchlings about: 1/8″ (first instar). They are ideal for smaller baby reptiles.
- Small 3/8″ – 3/4″ (second instar):
- Medium: 3/4″ – 1.1/4″ (third instar)
- Large: 1/4″ – 1.7/8 (fourth instar)
- Extra-large 1.7/8″ – 3″ (fifth instar)
Cost or price
By assessing their price various online vendors, their prices inclusive of shipment in the US is $10-$15 for 25-50 small silkworms, 20-25 medium, and about 15 large or extra-large ones.
In the UK, the prices are £4-£6 for 25-50 counts of small silkworms, 20-25 medium and about 15 large or extra-large one.
Prices in Australia and Canada seem similar. Buying in bulk and collecting them yourself may reduce these prices, i.e., cut off the shipping costs.
Not to overemphasis, these grubs require mulberry leaves to survive or mulberry chow. They cannot survive on other types except for Osage orange leaves (Maclura pomifera).
Also, they can eat lettuce, beetroot leaves, unpeeled carrot, and cabbage as an additional source of food and not as a replacement diet.
Fresh mulberry leaves
Their primary food mulberry leaves, with the white mulberry being the most preferred one over the red or black mulberry leaves. Mulberry leaves have a cis-jasmone odorant that attracts them. These grubs enjoy eating mulberry leaves.
Mulberry helps silkworms to have lighter colored silk cocoons, which many people prefer as opposed to B. mandarina (wild) that eat various foods and produce silk of different colors.
Commercial mulberry silk chow
If you do not get fresh mulberry leaves, you can look for the various brands of silkworm chows. Good ones include:
Coastal Silkworms Powdered Silkworm Food
This Coastal Silkworms have powdered silk food that comes in different amounts, i.e., they have ½ lb, 1 lb, 2lb, and 10 lb packages, and pre-made 1lb food and silkworm eggs on sale.
- Obtained from best quality mulberry leaves that make it closely mimic fresh mulberry leaves.
- It has a long shelf-life, making it possible to keep these worms throughout the year.
- It features an easy to prepare recipe where you need only need to add water and cook it in a microwave for about 5 minutes. In case you make more than enough, refrigerate it.
Once you have cooked and cooled the chow, grate it over these larvae. They will crawl over it and begin feeding. The pre-made one is fed directly but needs to be refrigerated.
An alternative you can buy is the Oregon Silkworms ½ lb powdered silkworm food, which works well too.
Make a chow yourself
Finally, if you have fresh mulberry leaves that are available seasonally, you can make this chow. It is not a difficult task. WikiHow has a recipe you can use.
Starting a colony
To begin your silkworm colony, you can either buy eggs or the worms themselves. Buying live grubs is suitable for a novice. Otherwise, experience breeders can buy eggs.
Buying silkworm eggs
Healthy silkmoth eggs usually are lemon-yellow and if they turn white after 2-3 days, they are not fertile. However, if they become black, they are viable.
You can order the eggs online. They usually come with a mulberry leaf or some chow. As you prepare your nursery, refrigerate in a zip lock bag. However, you should not freeze them.
Once your nursey is ready, gradually increase their temperature to 75 to 85 °F degrees F while keeping humidity at about 90 percent so that they do not dry.
These eggs can hatch at room temperature. However, an incubator will only help keep a stable temperature and fasten hatching.
If you are using an incubator, place them on a Petri dish with a damp tissue paper to keep humidity high and put them in the nursery.
When they are about to hatch, they will change their color to light bluish or gray.
Hatchlings or baby silkworms
Since hatchlings are vulnerable for their first up to two weeks, keeping them in an incubator at 78-85 degrees in a petri dish until after 10-12 days to increase their survival chances.
Also, add finely grate their food and let it be from younger tender mulberry leaves or silkworm chow. The petri dish must be well aerated.
An ideal place to keep your silkworm is a plastic container or tray with a lid and aeration holes. Unlike eggs, they need a lower humidity of about 50%. However, leaving them open may dry them out and dry their food faster.
Once they hatch, ensure they have food as these hatchlings must have food within a die or they may die. Grate fresh mulberry leaves or pre-made mulberry chow over them.
For large scale farming, consider having shelves to place your containers to help save space.
Finally, if you began with a small breeding container, you may need to move them to a large one to avoid overcrowding as it will cause condensation and failure.
When feeding them, ensure you wash your hand before handling them or their food to avoid transferring bacterial infections to them.
Their food should be free of any pesticides, herbicides, insecticides, or any other harmful farm chemicals as they will kill these grubs.
For hatchings, line their container mulberry leaves then grate their chow or fresh mulberry leaves into their container.
Afterward, add more food as you deem necessary since these worms are voracious eaters. While they can stay for a few days to a week without food, they will dehydrate and die.
Always, ensure their fresh leaves have a dry surface, i.e., there are no water droplets on the leaves as they can drown hatchlings. Furthermore, it can cause condensation, a significant cause of their death and failure.
Furthermore, excessive moisture and condensation forming will provide a moist environment that will favor fungal and mold growth.
Finally, a rough estimate of the amount of food they need is 2 lbs for 50 hatchlings until they pupate and turn into adults. Adults do not eat.
When they are about to begin spinning, provide them toilet paper tubes, egg cartons, baskets, berry boxes, twigs without leaves, chicken wire, etcetera, as a place where they can spin.
Once they have pupated, move them to another container where they will come out of their cocoon, mate, lay eggs, and die. Once you have eggs, their cycle begins again.
Caring for silkworms
Firstly, keep their habitat clean. Remove any moisty old food, cocoons, or wet droppings as they will encourage bacterial, mold growth, and condensation.
However, if they are dry, you can leave them in place. All you need to do is ensure the previous food dries before adding a new one as well as ventilate their container well.
To do this, add chow about half an inch in their container, give them a few hours to crawl on top of it, lift them off and dispose of the old food and feces.
Secondly, in the case of condensation, open their containers until they dry (for the condensation to dissipate. Overcrowding can also cause condensation.
Note that during the mulberry degradation, there might be a characteristic smell that is from the essential oils, flavonoids, and terpenoids that these leaves have.
Finally, when handling them, be very careful because their bodies are soft, and they can easily get bruised.
Besides raising silkworms to use as your pet feeder insects or for sale to other people who need them, you may also consider sericulture, which is the keeping of silkworms for raw silk. The Chinese, Japanese, and Koreans have practiced sericulture for over 5000 years now.
The Bombyx mori (domestic silkworm) accounts for most of the silk production in the world while other domesticated and wild Saturniidae moths such as the Assam silkmoth, Tussore moth, and Eri silkmoth make a smaller contribution.
In sericulture, after pupation, before they release enzymes to break the cocoon, which will damage the rather long raw silkworm filament, they are killed while inside their envelope using steam, boiled in water, or soaked in sodium hydroxide. Besides killing the pupae, it helps loosens the sericin gum making silk harvesting easy.
Afterward, take the boiled cocoon to buyers for yarn production where single filaments are then combined and reeled into a thread under tension. Then the thread is plied into yarn ready for sale. Usually, you need about 2500-3000 silkmoth cocoons to make a pound of raw silk.
After harvesting the raw silk, the dead pupae is a byproduct used as fertilizer, feed for poultry, pigs, fish, and ruminant or eaten in some places, especially in China (roasted silkworms), and in Japan, it is popular fishing bait.
Also, the pupas can be for oil extraction for industrial use in such as in making soaps, candles, varnishes, pharmaceuticals, plastic paints, and biofuel.
The pupas intended for human consumption are defatted to make them stay longer as well as increase their protein content when compared to undefatted ones.
You can use the silk liter, i.e., larvae excreta, mulberry residue, and sloughs from molting as a garden or farm manure.
Finally, you can sell silk cocoons, even in small amounts, and they will fetch something worthwhile your effort.