37: The puation cell of C. caucasus. This cell measures about
17 cm (6.75 in.). Even large cells such as this can prove delicate,
and care should be taken when working around them.
|(i - pupation)
Many cetoniine scarabs
complete their larval phase in just a few months, whereas some of the really
large dynastines take a year or more. When your scarab larvae reach
the maximum growth point in the late 3rd instar phase, they will slow down
in their eating, and begin construction of their pupal cells. The
pupal cell of a scarab larva is basically the same as the cocoon of a moth.
However, whereas a moth's cocoon would be made of silk produced by the
caterpillar, the pupal cell of a scarab is instead made of bits of wood
and leaves cemented together. The cement used to stick all of the
wood/leaf particles together is produced by a special gland in the larva.
|The function of
the pupal cell is to seal off the larva and protect it from the outside
world while it undergoes the delicate process of transforming to the adult
stage. Scientifically, the adult beetle is called an "imago".
This same term is used to describe the adult stage of all insects.
When the time for your larvae to pupate is nearing, you must exercise additional
caution whenever digging around in the substrate to perform periodic substrate
renewals, or just routine checks on the condition of the larvae.
The extra careful treatment is necessary because if you were to accidentally
damage the pupal cell of a larva as it was constructing it, it could upset
the larva greatly and threaten its very survival. Some species of
scarab larvae are not readily able to repair their cells once they have
been accidentally damaged. The pupal cells of cetoniines are usually
created in the upper and middle layers of the substrate. Dynastine
larvae nearly always build their cells at the lowest possible level, often
using the floor of the rearing container as the bottom wall of their cell.
Cetoniine larvae often construct their cells against the wall of the terrarium
as well, but they use the side walls rather than the floor.
|If you are using
a very transparent container such as a glass aquarium, glass bottle, or
clear plastic box, this habit of building the pupal cell against the walls
can often allow you to have a window into the cell throughout the entire
metamorphic process. In most cases however, the majority of your
larvae will build their cells away from the walls of their rearing terrarium,
and will rest freely within the substrate. This is especially true
of the cetoniine species. In dynastines however, the cell is almost
unfailingly built tightly attached to the very bottom of the terrarium.
Cells such as those are best left undisturbed, but the cells of smaller
cetonniinae which are not attached to walls or other objects can be handled
or moved prior to emergence of the adult beetle if needed. Be very
careful if you handle them, because the structure of some cells is quite
delicate, and can be ruptured if handled carelessly. Handle them
carefully as if they were fragile eggs. Even the large cell of a
dynastine scarab can appear deceptively robust and strong, but really they
are not and can be easily damaged through rough handling. If you
come across cells while doing a routine substrate change, and they need
to be moved, pick them up very carefully, as they don't become very solid
until the larva has completed work on the inside. Virtually no pressure
should be applied to the cell when picking it up at any time. The
cell should be placed back in the substrate at a similar level to that
in which it was found. If you ever happen to break a cell, it is
best to just place it back in the soil, fitted together as best as possible,
and cover it over. If the larva inside hadn't finished cementing,
it will usually repair the damage. If the cell already contained
a pupa, the break will not be repaired and the pupa may mold and disintegrate.
38: A large male pupa of Chalcosoma, here removed from its
protective cell for photographic purposes. If done extremely carefully,
it can be placed back inside its cell undisturbed, but ordinarily, pupae
should not be removed from their cocoons for observation by anyone except
the most experienced of beetle breeding hobbyists. In such cases,
the cell is carefully and precisely separated into two separate halves
which can neatly be placed back together, leaving no opening to the
outside environment. Ordinarily, the only reason to do this would
be in instances where one would seriously want to document the various
life stages in their entirety. Without a surrounding cell of precisely
the right shape, proper transformation to the adult stage is impossible,
and would cause great physical deformity upon emergence from the pupal
skin. The reason is because the pupa must undergo a series of specific
bodily rotations when emerging from the pupal skin, and it uses the cell
walls around it for leverage. If not able to rotate in a natural
manner, failure to emerge properly is almost inevitable.
courtesy of Al
|Once all of the
larvae within a rearing container have made their pupal cells, no further
substrate changes or food additions will be necessary. Pupation time
varies greatly depending upon species. Many of the small to medium
cetoniines can do it in 4-6 weeks, but most rhinoceros beetles take at
least a few months. In many cases, the larger the species you are
breeding, the longer you can expect larval durations to be, and the longer
you'll have to wait for pupation to be completed. Your beetles will
not all be emerging from their pupal cells at the same time, just as not
all of them pupated at the same time either. Instead, you will have
a period of time in which they will be emerging gradually, until eventually,
all have come out from their underground cells. At this time, you
will basically be back at the same point where you first started (assuming
that you began with adult beetles rather than larvae), and you will be
ready to breed your beetles all over again.
A question that often
comes up in the hobby of captive rearing beetles is whether or not repeatedly
breeding the same individuals back together is genetically harmful to them.
The answer is "possibly", but in my personal experience, I have never observed
any obvious abnormalities caused by inbreeding. When beetles occasionally
turned up that had physical deformities, it was always readily attributable
to an error in the pupation process, rather than a genetic abnormality.
If it is possible for you to introduce new genetic stock to your culture
of a beetle species every few generations, then that is something which
you may wish to consider doing. However, in my personal captive breeding
efforts with scarab beetles and many other insects, I have not found any
problems linkable to inbreeding, and it would appear that insects are not
affected by this process to the extent that vertebrate life forms are.
Lastly, I would like to point out that
the information presented in this manual is largely the result of my own
personal work experience with about a dozen different species of cetoniine
and dynastine scarab species. There are a number of other pages on
the internet that you should definitely visit to get a more rounded idea
of the techniques used by other hobbyists. I have included some important
links below. Some contain general instructions for the breeding of
all cetoniine / dynastine scarabs, while others are concerned with the
specifics of rearing certain species.
of the Beetles - (general)
Megasoma acteon - (Megasoma actaeon)