Silkworms: a Healthy
Alternative Feeder Insect.
Veterinarian Brett De Poister extols the virtues of a live food
source that has great potential for Australian keepers.
The silkworm is in fact the larvae of the Silkmoth
(Bombyx mori), which was domesticated over 5,000
years ago in China for the production of luxurious silk
garments. In the United States and Europe, silkworms
have also been produced commercially as a food source
for reptiles for more than two decades. Restrictions on
the importation of silkworms, lack of year-round avail-
ability and, of course, reliance on Mulberry trees have,
until more recently, prevented silkworms from becom-
ing a commonly used feeder insect in Australia,
however this is changing rapidly. slowing the progression of corneal lipidosis in Green
Tree Frogs.
The commercial availability of silkworms in the reptile
industry has prompted a number of studies over the
years, examining the nutritional content of silkworms
compared to that of other common feeder insects. The
unanimous conclusion has been that the silkworm is
highly nutritious, with several advantages over common
alternatives. Silkworms have a low fat content and are
high in calcium (with a better Ca:P ratio than some
other feeder insects) and contain highly digestible pro-
tein. In one study, silkworms were the only invertebrate
tested that contained detectable levels of preformed
vitamin A. Silkworms have also been found to contain
high levels of the vitamin B complex, and together
these substances play a major role in reptile health. Variety is the spice of life and we should aim to offer a
varied diet to our captive companions. There are many
benefits to be conferred by adding silkworms to your
pet’s menu, and their phenomenal growth rate makes
them ideal for the smallest of hatchlings right up to the
largest of lizards. Silkworms are a great addition to the
list of commercially available feeder insects, but for the
keen reptile keeper who enjoys raising their own food
items, silkworms are also fairly easy to keep and breed.
In addition, silkworms possess a modest exoskeleton
which allows optimal nutritional absorption. Meal-
worms (in particular), crickets and many other insects
have a chitinous exoskeleton with a sclerotized cuticle
that is very difficult to digest. Often, intact mealworm
and cricket carcasses are passed in the faeces of insec-
tivorous amphibians and reptiles, resulting in minimal
nutrient absorption.
Silkworms also produce a proteolytic enzyme called
serrapeptase, which allows the moths to break down
their cocoons when they are ready to emerge. This sub-
stance is widely used in human alternative medicine and
is associated with anti-inflammatory properties and
arterial plaque reduction. Benefits have also been
reported by reptile keepers around the world involved in
the rehabilitation of sick and injured reptiles, although
these are yet to be substantiated by clinical studies.
Unpublished reports credit serrapeptase with success in
Photo by Chris Watson.
The Japanese have used silkworm pupae for centuries in
breeding koi and have associated the use of silkworms
with fast growth rates and pure white colouration. They
claim the enzymes contained in the silkworms promote
optimum liver health, allowing the koi to excrete toxins
more efficiently and yielding a strong immune system
and pure white skin, which would otherwise have a dull
appearance due to build up of toxins in the tissue.
Silkworms are best maintained at temperatures over 22°
C (ideally 24°-27°C), but very little equipment is
required – remember the shoe box worked great in
primary school! Once the worms are set up, provide a
constant source of food and they will grow very
quickly. Traditionally, Mulberry leaves were required to
successfully rear silkworms. A Mulberry-based food,
often referred to as ‘silkworm chow’, is now available
which allows silkworms to be raised year round without
the need for access to a Mulberry tree. Silkworms go
through five different instar stages, with each change
preceded by a moult. Prior to moulting they will stop
eating and raise their heads in the air as if they are
praying – it is best not to disturb them at this time.
Cleanliness is the key to rearing silkworms. The cater-
pillars eat a lot and as a result poop a lot too. Mould and
bacteria love to grow on old moist chow, mulberry
leaves and frass (silkworm lingo for poop) so it is
important to clean out old food and frass daily and
frequently transfer the worms to a new, clean container.
It is also important to thoroughly wash your hands with
soap and water prior to handling silkworms or their
food, to prevent contamination with unwanted ‘bugs’.