Feeding silkworms to Leopard geckos

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Silkworms (or 'silkies') are the larvae of the Mulberry silk moth. Being high in protein and low in fat, they are considered a great food for Leopard geckos.

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Introduction

Silkworms are the larval (or caterpillar) stages of the Mulberry silkmoth (Bombyx mori). As a foodstuff for Leopard geckos, they are known to be high in protein and low in fat. Although their natural life cycle is seasonal (see the silkworm life-cycle later), silkworms are easy and cheap to keep and culture. Other than food items for Leopard geckos and other reptiles, silkworms are popularly cultured on large scale for their ability to produce silk.

In some countries, silkworms are readily available from specialised pet shops and online retailers (e.g. Amazon.com). Silkworms are quiet, slow-moving, fairly odourless, need little maintenance and relatively small amounts of space.

Silkworm nutritional values*

Silkworms offer great value as food for Leopard geckos. When looking at their nutritional composition, they are high in protein, various vitamines, calcium and other minerals. Silkworms are also low in fat:

* Values are averages calculated from sources. Expressed as %DM except moisture.

When comparing silkworms with other crawling food such as mealworms (T. molitor), they have similar amounts of protein (ca. 59%(5)(17) vs. 54%(1)(2)(4)(5)(6)(8)(9)(14)), less fat (ca. 17%(5)(17) vs. 30%(1)(2)(5)(6)(7)(8)(9)(14)), more usable calcium (Ca:P ratio of about 1:2(13) vs. 1:14(5)(6)(8)(9)(11)(14)(18)) and are considered just as tasty.

When compared to crickets (A. domestica), silkworms have similar protein levels (ca. 64%(3)(5)(6)(8) vs. 59%(5)(17)), less available calcium (ca. 1:5(6)(8)(18) vs. 1:2(13)) and similar amounts of fat (21%(3)(5)(6)(8) vs. 17%(5)(17)).

Silkworm sizes

  • Hatchling/first instar about 3 mm
  • Second instar 9-19 mm / 3/8  – 3/4 ″ (small silkworms)
  • Third Instar 19-31 mm  / 3/4 – 1 1/4 ″ (medium silkworms)
  • Fourth instar 31-44 mm / 1 1/4 – 1 7/8 ″ (large silkworms)
  • Fifth instar 50-75 mm / 2 – 3 ″ (x-large silkworms)
  • Moth has a wingspan of 40-50 mm / 1.5 – 2 ″

Feeding silkworms to Leopard geckos

When available, silkworms can be fed to any size and age Leopard gecko. They are considered palatable (tasty) and are readily accepted by Leopard geckos and other insectivorous reptiles — making them a great choice for picky eaters too.

Silkworms have soft bodies that make them easy and safe to swallow and digest. Because of their high protein and available calcium levels, they are popularly fed to gravid female and growing Leopard geckos.

Silkworm life cycle

As mentioned earlier, silkworms are the caterpillar stages of Mulberry silkmoths (Bombyx mori). First instar caterpillars hatch from eggs after which they will eat and grow through several larval stages before pupating and emerging as a silkmoth again.

Bearded dragon silkworm life cycle

The life cycle of silkworms (Bombyx morio). (1) Egg. (2) First instar. (3) Second instar — small silkworm. (4) Third instar — medium silkworm. (5) Fourth instar — large silkworm. (6) Fifth instar — extra-large silkworm. Image by B kimmel (CC BY-SA 4.0)

Newly hatched silkworm larvae are very tiny and will eat for anything between 12 and 56 days, consuming large amounts of mulberry leaves. The time it takes a silkworm to grow is dependant on the environmental temperature and the availability of food. Colder temperatures will prolong this period. During their growth period, they will moult four times. The times between their moltings are called instars. The larvae of all four these stages (collectively called silkworms), can be fed to Leopard geckos(32).

After the last moulting and being about 50-75 mm / 2-3 ″, the silkworm will stop eating and spin a cocoon from its own silk. Metamorphosis (changing into a moth) will take two to three weeks to complete. Moths that emerges from the cocoon will not eat at all. Their only goal is to find a moth of the opposite sex, breed and lay eggs again. A female silkmoth can lay anything from 200-500 eggs. Silkmoths are generally not fed to Leopard geckos.

Conclusion

Silkworms are popularly fed to Leopard geckos as part of a varied diet. Their ease of culture, feeding safety, high protein and calcium content and palatibilty put them high up in the chain of favourite feeder insect to Leopard geckos.

References

Cited references

For URL links, see the Reference article page.












18) Wilson Bessa, Leah (December 2016). The evaluation of the potential of Tenebrio molitor, Blatta lateralis, Blaptica dubia, Hermetia illucens and Naupheta cinerea for human consumption. Thesis (MSc) - Science in Food Science in the Faculty of AgriSciences at Stellenbosch University