The
Breeding/Rearing of Goliathus (page 3)
- Karl Meier
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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. |
.
The
eggs of G. goliatus. Goliathus 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. |
.
.
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. |
|
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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. |