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The Breeding/Rearing of Goliathus

By Karl Meier
(web version arranged by C. Campbell)

With the permission of coleopterist Karl Meier (Germany), I have assembled the following pictorial manual (with supplemental photographs from various other hobbyists) in which he describes his captive breeding technique for Goliath beetles.  I extend my appreciation to Mr. Meier for making his research available for viewing here at the GOLIATHUS website, and also wish to thank hobbyists Matthias Frei (Switzerland), Fan Lin (Japan) and Bibitte for providing additional photos.  I am certain that many beetle hobbyists will benefit greatly from the techniques discussed in this presentation.

You may also be interested in reading the following articles contributed to my Family SCARABAEIDAE website by hobbyist Yasuhiko Kasahara (Japan):
The Breeding/Rearing of Prosopocoilus giraffa keisukei
The Breeding/Rearing of Dynastes hercules hercules

1. Introduction

    Inhabitants of Africa's great equatorial forests and and sub-equatorial savannas, the Goliath beetles (genus Goliathus) are among the largest and most spectacular members of the family Scarabaeidae, and most certainly the largest of the Cetoniinae (Flower scarabs).
 

    The closest relatives of Goliathus are the genera Argyrophegges, Fornasinius and Hegemus.  In recent years, the captive breeding of Goliathus has become more popular with beetle hobbyists as a better understanding of the particular needs of these insects has been gained.  Although one of the more demanding cetoniine scarabs to rear, with some patience and effort, it is certainly possible to maintain Goliathus over multiple generations.
G. goliatus (pair) - Image  Matthias Frei
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A pair of Goliathus goliatus (wild collected in Cameroon).  The male in this photo measures 10 cm (4 in.), which is at the upper limit of the size this species generally attains.  Photo courtesy of Matthias Frei.

    While it appears that relatively little is known about the exact biology of these beetles in the wild, through considerable trial and error over the past decade or so, an effective captive rearing procedure for this genus has been established.  Among the scarabs, Goliath beetles are indeed unusual in their particular requirements, and the methods used for rearing them differ from those of most of the other cetoniine species that have long been in culture.
 

G. goliatus (male) - Image  Matthias Frei
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The same male as shown in the above photo.  This beetle weighs 42 grams.
Photo courtesy of Matthias Frei.
    Although it is usually rather easy to encourage gravid females to deposit eggs, the captive reproduction of Goliathus beetles was problematic until quite recently.  The two key factors for successful breeding were the discoveries that the larval stage needs to be provided with a high protein diet on a consistent feeding schedule, and that the pupal stage requires specific environmental conditions in order to avoid high mortality rates and other complications.

2.  Adults and egg production

    For the purpose of egg-laying, a substrate composed of approximately 60% well-rotten deciduous hardwood (pulverized to a rather fine particle size) and 40% organic, high peat content commercial potting soil (or alternatively, pure peat) works well.  Both of these components should be thoroughly mixed together until of uniform consistency.
 

    A substrate of 100% rotten wood can be used if desired, although the addition of peat is helpful in maintaining an even distribution of moisture throughout the substrate.  If peat is unavailable in your particular area, coconut coir (a peat-like material made from pulverized coconut husks) can be substituted for it.  Some commercial brand names for this product are Lignocel, Coco Peat, and Bed-A-Beast.  It is sold at pet stores and garden centres in the form of compressed, dehydrated blocks which are then soaked in a bucket of water until fully expanded.  The material is then tightly squeezed by hand to remove excess water.
Goliathus breeding substrate - Image  Karl Meier
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A suitable breeding substrate for Goliathus can be made by mixing 60% rotten deciduous hardwood (pulverized) with 40% quality, commercial potting soil.  Photo courtesy of Karl Meier.

    The proper moisture level for Goliathus breeding substrate is the same as that used for most other Cetoniinae.  The substrate should be moist, but not truly damp.
 

G. goliatus (male) - Image  Matthias Frei
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 A freshly emerged male G. goliatus which displays brilliant reddish brown elytra (captive reared).  Photo courtesy of Matthias Frei.
    If a handful of the material is squeezed tightly, and only sticks together very momentarily upon being released, then it is probably at approximately the right moistness.  Another useful test for determining the substrate's moisture level is to tightly pinch a small amount of it between your thumb and forefinger.  If a drop of water falls freely from it, then it is certainly too damp.  If water only appears slightly between the fingers yet does not drip, the moisture is correct.

    To ensure that you do not initially add too much water to the substrate, begin by adding only a small amount.  If it is still too dry after thorough mixing, continue adding water in small increments until the substrate reaches the desired moisture level.  If your substrate material is too wet from the start, or if you accidentally add too much water upon mixing it, spread the materials out in a thin layer on a large plastic sheet and place it in a sunny area until the excess moisture has been evaporated.

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