Keeping sun beetles

Article on keeping and breeding the sun beetle, published in Practical Reptile Keeping

1. T
he sun beetle (Pachnoda
marginata) is a fascinating and
widely available species of
fruit beetle. Sold
frequently under the guise of
Pachnoda grubs, these
invertebrates are often
simply used as live food for
reptiles and amphibians.
However, sun beetles are
very interesting to
maintain, possessing vivid
colours and a fascinating life
cycle. Despite having been
kept for some time now, this
brightly coloured beetle’s biology
is still not fully understood, offering
plenty of scope for study.
In the wild
Sun beetles were originally sourced from
areas of west and central Africa. While P.
m. peregrina is easily the most common
example seen in UK collections, other
Looking for a colourful, interesting and inexpensive invertebrate to keep
and study? Here’s an idea from James Brereton MSc.
sun beetles
Keeping
subspecies are also available to
breeders. There is a varied range
of nine recognised subspecies
in total, some of which have
no patterning on the
upper surface of the
body.
These invertebrates
occur in tropical
rainforest habitats, and
their diet consists of ripe
fruit. Adult beetles have
a well-developed sense
of smell, and are able to
navigate toward fruiting
trees. They are able to fly,
which not only assists them to
reach fruit but also to track down
potential mates more easily as well. In
order to fly though, the beetle must first
warm its body by muscle contractions - a
surprising skill for a small invertebrate!
Once its body temperature has reached
the required level, the beetle is able to
take off and fly, albeit rather noisily and
clumsily, toward its target.
Their eggs are laid on wood substrates
or within the soil, and over time, the tiny
white larva will start to hatch out. These
larvae are humivorous, or soil-eating, and
live within the leaf litter or in rotting
wood until they reach sufficient size to
progress to their next life stage. This will
take several months. Interestingly, sun
beetles have been found in some other,
more unusual substrates though: Orozco
& Philips (2012), for example, found P.
marginata grubs developing in guano in
a bat cave, which reflects their
remarkable adaptability!
Much like the mealworm and other
beetles, the sun beetle has a pupal phase.
However, in order to protect itself during
this critical phase of development, sun
beetle grubs also build a cocoon – an
oval-shaped cell constructed from
substrates in the environment. Typically,
the cocoon is made out of soil, but the
‡ These beetles can fly
effectively, in spite of
their size.
14 | Practical Reptile Keeping

2. FEATURE |sun beetles
‡ These beautiful invertebrates have been the subject
of various scientific studies, but there is still much that
remains to be discovered about them.
†
potentially pest control organisations, are
again of only limited use to breeders.
Peer-reviewed information on their
breeding and biology in the form of
scientific papers is comparatively scarce.
Studies, therefore, on enclosure use and
behaviour are to be encouraged to help
keepers gain a better understanding of
the needs of these invertebrates.
Environmental variables
Many care sheets recommend keeping
sun beetles at temperatures varying from
20-28°C (68-82°F). At present, however,
there is relatively little proven information
on the ideal temperature at which to
maintain these beetles. Average figures
for central and West Africa, however,
seem to reflect these temperature
parameters. For example, information
from Accra, Ghana – a region known to
contain this species - shows temperatures
ranging from 24-32°C (75-90°F)
depending upon the time of year.
The recommended humidity level for
sun beetles is around 60%, and again, this
figure is also similar to data from Accra,
indicating that the humidity there
fluctuates from 60% to 90% year round,
rising during rainy periods. It is known
that humidity levels below 25% are
unsuitable for sun beetles, rapidly leading
to beetle mortality. To maintain a high
humidity level, it is recommended that
the enclosure soil is maintained in a
damp state through regular spraying, to
keep the soil moist, but not saturated.
This is also important for the successful
growth and pupation of grubs.
Housing
It is important to remember that sun
beetle larvae, pupae and beetles all have
different biological requirements. As
such, sun beetle enclosures need to be
multifunctional, in order to
accommodate all life stages.
A range of enclosure types may be
cocoon may also contain chunks of wood, stone and leaf litter.
Few studies have investigated the
behaviour and biology of sun beetles out in the wild, and the predominant focus for studies has been methods of controlling their numbers. Many Pachnoda species are considered pests throughout their home ranges because
of the way that they attack fruit crops.
These population control investigations
are not really of value to those keeping
and breeding sun beetles.
Studies on sun beetles
Thanks to the ease of breeding and
maintaining sun beetles, members of this
group have been widely kept in
laboratories across the globe. For
scientists, the areas of key interest for
study have been largely:
■ The microflora (beneficial bacteria and
other components) in the digestive
system of Pachnoda larva.
■ The microbiological structure of the
body systems of adult beetles.
■ The attractiveness of different chemical
odours to adult beetles.
These studies, while both interesting
and useful for microbiologists and
JUNE 2016 |15
‡ Minimum (blue) and maximum (red) temperatures over the course of a year, set out
on a monthly basis from Accra, Ghana. Downloaded courtesy of https://weatherspark.
com/ which is a great site that allows you to track climatic parameters across the
globe. Provided that you know where the species that you are keeping originates, this
then allows you to work out the key environmental parameters for its care.
ˆ It is not just temperature readings that you can obtain from https://weatherspark.
com/ because invaluable humidity data is also available. This shows the corresponding
annual maximum (blue) and minimum humidity levels for Accra in Ghana, giving a clear
guide as to what level is required by sun beetles. You can even check out cloud
coverage as well on this site. Downloaded courtesy of https://weatherspark.com/

3. used, including the acrylic tanks normally
used for stick insects. Exo Terra™ and
Komodo™ enclosures can be highly
suitable, but old fish tanks can also be
adapted – provided that adequate
ventilation is incorporated into the
design. Adult beetles are unable to climb
up glass or acrylic walls, but once
sufficiently warm, they are capable of
flying out of enclosures. A lid of some
type is therefore a necessity.
Substrates
A deep substrate is a requirement for
successful breeding of sun beetles. The
larvae are very specialised, feeding on soil
and plant matter, and studies have
shown these grubs can digest highly
fibrous material. They depend on an
unusual digestive method known as hind
gut fermentation, which means they use
microbes to break down their food for
them (Egert et al, 2003). In order to
provide suitable foods for your grubs,
create a mix of rotting wood, soil and
decomposing leaves. Provided this is kept
at a suitably warm temperature, your sun
beetle larvae should thrive in this
† The patterning of this
group of beetles, while
attractive to our eyes,
may help to camouflage
their presence, by
breaking up their body
shape, and protecting
them from predators.
16 | Practical Reptile Keeping
environment.
Some keepers recommend burying
fruits and vegetables into the soil for
grubs to eat. Although foods of this type
may be eaten, it is not necessary, as these
invertebrates are fully capable of
digesting leaves and wood, but as
explained later, potato may be useful.
Adults will also bury themselves in the
soil at night. Even if you are not intending
to breed your sun beetles, provision of
soil is still a requirement for good
husbandry. Furthermore, if you’re keeping
a colony of sun beetles together in the
long term, you will need to change the
soil. Remove some of the processed,
digested soil – this will look like small
pellets. Add in new leaf litter and rotting
wood to ensure that new larvae have a
constant supply of food.
Nevertheless, try to avoid disturbing
the pupal cells of the developing beetles
as much as possible. These are oval-
shaped objects, sometimes bored into
wood or attached to furnishings in their
quarters (such as the wall of the
enclosure, perhaps). When you find these,
place them back without delay. The
pupae need warmth and minimal
disturbance to develop into beetles.
Feeding
The food required by the larvae has
already been covered, and pupae of
course, wrapped in their cocoons, have
no need for food. Adult beetles, however,
unlike their larvae, have a much simpler
digestive system and are unable to live
off fibrous foods such as decomposing
leaves. Instead, adults require the
provision of fruit and vegetables in order
to thrive.
ˆ Adult sun beetles such
as this
Pachnoda aemula
individual will bury down
into the substrate at night.
‡ Adult sun beetles feeding on banana. Photo courtesy Evanherk.

4. FEATURE |sun beetles

given lights in the enclosure, sun beetles
will climb up branches and live plants in
order to bask. This may be partly to
increase their body temperature and
activity levels. When provided with a low
level (2.5%) UV (ultraviolet) light source in
their quarters, sun beetles have been
noted to spend long periods basking.
It is now strongly recommended to
provide light for basking and increasing
the activity levels of these invertebrates. If
there is no light attached to your
enclosure, try to place your sun beetles in
a place where they will receive natural
light, or light from a reptile enclosure, but
Sun beetles are equipped with an
impressive ability to detect fruit odours
(Stensmyr et al, 2003), and it seems that
foods such as banana, melon and mango
are preferred. Most fruits are taken to
some extent, and there is a need to
provide at least one type of fruit at all
times to keep all animals well fed.
Lighting
Sun beetles can and have been bred
without any specialised provision of
lighting. However, there is increasing
evidence that light is important for the
behaviour and welfare of this species. If
JUNE 2016 |17
obviously, you need to be sure that this does not impact adversely by raising the temperature and lowering the humidity within their enclosure. Never leave their quarters in front of a window in the sun – this will give them no UV benefit, because UV light is blocked by ordinary window glass.
Enclosure furnishings
In order to bask, sun beetles need to have branches, twigs or live plants to climb. This is an important component of enclosure design. As with many invertebrate enclosures, live plants are ideally recommended, providing behavioural enrichment for your beetles.
One problem that often emerges in
planted enclosures for this species is that
plants often die off. The difficulty is that
grubs moving through the soil may
dislodge and damage the roots, while
adult beetles may actively destroy the
leaves and stems of the plants above
ground. If the terrarium is well designed
and the plants have been given time to
root before beetles have been
introduced, however, this may not be a
significant problem, particularly if a plant
light such as Jungle Dawn (Arcadia) is
incorporated here. But always bear in
mind that a large colony of beetles may
have highly detrimental effects on any
live plants in the enclosure.
One way to combat this is to
incorporate fast growing plants into the
enclosure. Such plants can provide both
important climbing opportunities and
basking areas for the beetles. A range of
grasses may be suitable, but one of the
most widely available plants suitable for
this purpose is the humble potato
(Solanum tuberosum). If planted in the
soil of the enclosure, supermarket
potatoes will rapidly sprout. Within
roughly two weeks, these should provide
stems for beetles to climb up, and also
vegetable matter to supplement the diet
of the larvae.
ˆ A large number of sun
beetles basking on wood
in the collection at
Cincinnati Zoo in the USA.
Photo by Greg Hume.
‡ All stages in the beetle’s lifecycle (aside from the eggs) can be seen here, with a pupal casing (left), a grub (centre) and an adult beetle (right).
Photo courtesy of the author.

5. Maintaining a colony
If housed correctly, P. m. peregrina may
breed very successfully in terrarium
surroundings. Potentially, this may be
useful for sourcing larval food for your
amphibians and reptiles. If you are
planning to keep a colony for a long
period of time though, try to find
enclosures large enough enabling your
colony to grow. A bigger enclosure will
mean that your leaf litter substrate will
last longer, and grubs themselves will
have better nutrition. Such enclosures will
also give beetles sufficient space to move
around and breed as their numbers
increase.
Sun beetles can be housed with other
species, and successful colonies of beetles
have been kept alongside the Indian stick
(Carausius morosus) and the golden-eyed
stick insect (Peruphasma schultei). Some
success has been achieved with a
combination of sun beetles and the
Madagascar hissing cockroach
(Gromphadorhina portentosa) as well,
providing adequate areas are given for
both species to move around.
However, there are many key points
about sun beetle biology that are
currently not completely understood. For
example, breeding behaviour, while
witnessed, is not well documented, while
feeding preferences and larval maturation
times still need to be fully investigated. In
fact, even the lifespan of adult beetles has
particular individual is still actively
climbing over seven months after
emerging from its pupal stage. If we don’t
know how long these animals even live,
what else still needs to be discovered
about the biology of these invertebrates?
Other species:
■ P. m. peregrina is an excellent choice to
allow you to develop experience with
this group of beetles, thanks to its wide
availability and the ease with which it can
be bred. If you are interested in furthering
your beetle collection however, a range
of other brightly coloured choices exist,
which can be obtained from specialist
invertebrate suppliers. These include:
■ Golden sun beetle (Pachnoda
marginata aurantia): this related
subspecies is considerably rarer in the
hobby than P. m. peregrina, and it
possesses a beautiful golden brown
colouration.
■ Garden fruit chafer (Pachnoda sinuata):
a smaller species, displaying vivid yellow
and black markings. Easily available to
purchase.
■ Metallic fruit beetle (Coelorrhina
hornimani): this species has a shiny,
metallic wing case, and males are
unusual in possessing a horn.
■ Purple jewel beetle (Smagdethnes
africana oertzeni): a small yet stunning
purple species, which lives up to its name
in an enclosure.
This list is by no means exhaustive
though, and simply serves only to
confirm the variety of other species that
are available for beetle enthusiasts.
18 | Practical Reptile Keeping
not been accurately determined.
Lifespan
Many care sheets suggest the lifespan of adult beetles, from emergence for their pupa to death, can be anywhere from three to a maximum of five months. However, in a current ongoing study in which sun beetles have been given individual identification marks, some beetles have displayed surprisingly long lifespans, calling these figures into
question. Several beetles have reached
an age of over six months, and one
Did you
Male and female sun beetles can be
sexed very easily. Male beetles
possess a thin line running centrally
down the underside of their abdomen.
In contrast, females have no line here.
know?
ˆ You can keep these
beetles in the company of
other invertebrates, such
as the Indian stick insect,
provided the design of the
enclosure caters
adequately for both
species.
‡ An adult beetle in an
enclosure with sprouting
Crassula leaves. These
succulents are very easy
to grow and shallow-
rooted, so they are less
likely to be affected by the
burrowing grubs.
Photo
courtesy of the author.

6. FEATURE |sun beetles
Further
■ Brereton, J. (2014). Sun beetle
husbandry data sheet. ABWAK husbandry
guidelines. Retrieved from www.abwak.
com.
■ Egert, M., Wagner, B., Lemke, T., Brune,
A., & Friedrich, M. W. (2003). Microbial
community structure in midgut and hindgut
of the humus-feeding larva of Pachnoda
ephippiata (Coleoptera: Scarabaeidae).
Applied and Environmental Microbiology,
69(11), 6659-6668.
■ Orozco, J., & Philips, T. K. (2012).
Pachnoda marginata (Drury) (Coleoptera:
Scarabaeidae: Cetoniinae) Developing in Bat
Guano in a West African Cave. The
Coleopterists Bulletin, 66(4), 378-379.
■ Stensmyr, M. C., Larsson, M. C., Bice, S., &
Hansson, B. S. (2001). Detection of fruit-and
flower-emitted volatiles by olfactory
receptor neurons in the polyphagous fruit
chafer Pachnoda marginata (Coleoptera:
Cetoniinae). Journal of Comparative
Physiology A, 187(7), 509-519.
■ Weatherspark. (2016). Average weather
for Accra, Ghana. Weatherspark. Retrieved
from https://weatherspark.com/
averages/28541/Accra-Greater-Accra-
Ghana.
reading
JUNE 2016 |19
AD
In summary
The sun beetle is very easy to acquire from many live food suppliers and pet shops. This particular beetle is both rewarding and easy to breed and yet despite its popularity, the sun beetle has been rather overlooked in terms of research. There is a large amount of information that still needs to be determined about the behaviour and
biology of this invertebrate. If you are
interested in studying species that you
keep, it certainly presents some exciting
opportunities for further research.
✥
‡ The lifespan of the adult beetles may be longer than
thought, according to an on-going study.
The stunning metallic
flower beetle.