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The Breeding/Rearing of Goliathus (page 3)
- Karl Meier -
 
3. Larvae

    Like all scarabs, the larval stage of Goliathus has three developmental stages, or instars - L1, L2 and L3.  The larval skin is shed when progressing from L1 to L2, L2 to L3, and L3 to pupa.  Experience indicates that it is preferable to allow the larvae to hatch in the breeding terrarium, rather than excavating them for hatching in separate containers.  The reason is because the eggs of Goliathus appear to be especially sensitive to being removed from the substrate in which they are deposited by the female.  When larvae are present, you will usually start to see small, meandering tunnels along the walls of the terrarium (assuming that the walls are transparent).  It is best not to to remove larvae from the terrarium until they are at least two weeks of age.  When searching the terrarium for larvae, avoid digging into the bottom 8 cm of substrate.  This compacted bottom layer should be left undisturbed, as this is where any un-hatched eggs will be located.

    Goliathus larvae are best reared separately.  Like those of several other genera of large African cetoniines (e.g. Mecynorhina, Chelorrhina), the larvae of Goliathus have cannibalistic tendencies.  Because of this, along with the fact that they generally grow more quickly and larger when separated, keeping each larva in an individual container is the only practical method of maintaining Goliathus larvae.  They are rather unusual among the cetoniine scarabs in that they require a diet high in protein.

G. goliatus (eggs) - Image  Fan Lin
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The eggs of G. goliatusGoliathus eggs measure 4 mm x 2 mm in upon being deposited, but gradually expand as they develop over a period of 12-14 days.  Shortly before hatching, the egg's membrane becomes transparent, and features of the tiny larva within can be seen. Photo courtesy of Fan Lin.
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G. goliatus (1st instar larva) - Image  Fan Lin
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An early 1st instar (L1) G. goliatus larva.  Larvae this young must be handled carefully to avoid causing them any injury.  Photo courtesy of Fan Lin.

 
G. goliatus X G. orientalis hybrid (3rd instar larva) - Image  Karl Meier
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G. goliatus X G. orientalis hybrid (3rd instar larva) - Image  Karl Meier
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G. goliatus X G. orientalis hybrid (3rd instar larva) - Image  Karl Meier
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Several views of a late 3rd instar (L3) Goliathus larva weighing 73 grams.  This larva is a G. goliatus X G. orientalis hybrid (images of adult hybrids can be seen at the end of the manual).  Photos courtesy of Karl Meier.
    Extensive testing of various food types has been performed to determine which ones Goliathus larvae will most readily accept, and it has been found that the best results are achieved when they are given pellets of soft-moist cat or dog food (not to be confused with the wet food that comes packaged in cans or foil packets).  Soft-moist food generally has a moisture content of between 35-40%.  It resembles dry pellets, but it is soft instead of hard.  Pellets of dry cat or dog food can also be used, but are not usually well accepted.  The frequency of feeding (and removal of any uneaten food from the previous feeding) is extremely important.  Optimally, the food should be replaced every four days, and no less often than every five days.  Feeding more frequently than this will risk causing the larvae too much stress, which can lead to developmental problems.  It is important to offer only what can be almost entirely consumed within this period - if too much is given, the excess will become moldy and/or cause an undesirable proliferation of substrate pests such as scavenger mites (which although only the size of sand grains, can quickly become very numerous).  Over the course of four or five days, a large L2 larva can eat 4 pellets (each measuring roughly 1 cm long), and a large L3 larva can usually eat between 8-10 such pellets.  The most effective and time-efficient means of removing any uneaten leftovers and frass (larval droppings) is to shake the entire contents of the larva's rearing substrate (minus the larva, of course) through an ordinary kitchen sieve.  Unlike that of the breeding terrarium, the substrate used for rearing the larvae need not be formulated to provide nutrition, as once L1 stage Goliathus larvae have had about two weeks to grow, the amount of nutrition that they are able to derive from the substrate itself becomes negligible.

    Like those of certain other cetoniine genera (such as Cotinis spp.) the larvae of Goliathus live in soil instead of material such as rotten wood or accumulations of decaying leaves.  A substrate composed of 100% organic potting soil, or a mixture of 50% potting soil and 50% peat works well as a light, well-aerated, soil-type substrate for larvae once they have been isolated and you begin providing food pellets to them on a regular schedule.  The moisture level of substrate for rearing larvae should be somewhat drier than that used in in the breeding terrarium - only about 60% as moist.  Unless isolated from the breeding cage prior to L2 and given high protein food, Goliathus larvae will eventually die from starvation.  It appears that the ability to survive on nutrient bearing substrate (containing decayed wood and leaf particles, for example) for a short time after hatching is an adaptation that allows the larvae to gain enough size and strength to pursue more protien-rich fare, whatever this may be in the wild.  Under captive conditions, post-L1 Goliathus larvae have regularly been observed to actively hunt and eat smaller beetle larvae and other insects including crickets, and the fact that Goliathus larvae have a sharp, retractile talon on the end of each leg seems to suggest that they may in fact be predatory.  In captivity however, the procedure for feeding live prey to Goliathus larvae would not only be very expensive, but much more problematic and time consuming than using processed, pelleted food.  In any case, the rearing experiences of multiple hobbyists have confirmed that the use of live food is certainly not necessary for achieving maximum growth potential.

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