by Michael P.T. Gillett
(This article appeared in the October 1992 issue of the Newsletter.)
When I first came to Al Ain for an interview visit, I asked someone connected
with the ENHG about beetles. "Never seen any," they said. "Oh!
Except for the sacred scarabs out in the desert." Well, having been here
myself for nine months, I am afraid that I have to disagree on both points. The
UAE has a magnificent beetle fauna, but there just ain’t no sacred scarabs!
I have examined several hundred of scarab beetles from around the region and
I have to say that all of these have keyed out to Scarabeus cristatus
F. and not S. sacer L. or the closely related S. gangeticus
Cast.. The salient features of S. cristatus include possession of
a median sharp tooth on the forehead (lacking in the other two), thick red hair
on the legs and smaller size. Of course, this is not to say that it is S.sacer
alone which is depicted in the ancient Egyptian tomb paintings (since all three
spp. are similar and all occur in Egypt). It is just that the Latin name was
affixed to the only one of the three which occurs in southern Europe. Some quite
different scarabaeid beetles were also portrayed on ancient Egyptian artefacts
and these can be identified as belonging to the genera Hypselogenia,
Copris, Catharsius and Gymnopleurus.
Of these, the last two are represented in the U.A.E. by at least a brace of
species each (although these have yet to be determined). There are also many
other smaller species belonging to the genera Onitis, Cheironitis,
Onticellis and Onthophagus amongst others. The
massive Heliocopris gigas, also belongs to this family
(Scarabaedidae) and is one of the largest Arabian beetles, but it has yet to be
found by me.
Of the beetles mentioned, only Scarabeus and Gymnopleurus
are "ball rollers", but there are other genera in neighboring
countries (Mnematium, Anomiopsis, Eueranium
etc.). An interesting feature of all except Gymnopleurus, is the
absence of tarsi from the front legs. This modification is an adaptation to the
ball-rolling habit and is shared by many neotropical species of dung beetle
(e.g. Phaneus from Brazil). If you have ever had the opportunity
to watch the activity of these beetles, you will know that, not only is it
interesting and at times downright funny for the observer, but it is also a
serious business for the scarab(s) involved. S. cristatus is
mainly nocturnal, but can be found in the late afternoons during spring rolling
balls made generally from camel dung. The balls are not the actual faecal
pellets of camels but rather are re-constructed from chopped-up dung (the shapr
teeth on the front of the head and front tibiae are used for this). The balls
are perfectly spherical and vary in size from less than 2.5 to more than 4.5 cm
diameter and are constructed for two different purposes. Smaller balls, seen
being propelled around by a single beetle, are often just for the feeding
requirements of that one adult. Large balls are sometimes manouvered by a pair
of beetles, but usually only by a single female, and are intended for
reproductive purposes. During the transporting process, there is always the
possibility that other scarabs will attempt to dispossess the original owner.
Fights take place and, I am glad to say, it is usually the owner who wins. Using
the height of the ball as an advantage by gripping it with the middle and rear
legs the owner uses the powerful front legs to topple and even invert the
assailant. Whilst I have not seen this behaviour with S. cristatus,
I have watched it many times with S. semipunctatus F. in Italy.
If you are lucky enough to come across S. cristatus in the
action of rolling a ball and you have a few minutes to spare, it is really quite
good fun to follow and watch what happens. The ball is propelled backwards by
the beetle whose sense of direction does not appear to be too crucial to the
proceedings. At any rate, going round in big circles and up and down the same
sand dune seems to be part of the plan – perhaps a devilishly fiendish one
intended to throw off pursuit by the erstwhile ball rollers! The funniest
moments (for the observer) are when half-way up a slope, control is lost and the
ball, with the beetle still clinging to it, gathers momentum and crashes down to
the bottom again --- rather like a scene from Tom & Jerry! However, our
scarab is nothing if not determined; a second attempt is quickly made, and
usually proves successful. Eventually, after 50 or even 250 metres of up-dune
and down-dune, the ball is brought to rest (usually on a gently sloping patch of
firm, bare sand) and the driver jumps down. Sand begins to fly in all directions
and within about half a minute the ball is superficially buried. The scarab next
begins to dig a horizontal tunnel away from the buried ball. At this stage,
there are frequent comings and goings at the entrance to the burrow as the spoil
is removed (and generally left on top of the buried ball!). After about five
minutes, the scarab emerges and then, with something akin to the panic shown by
a woman who has lost her handbag, a frantic search for the buried ball begins.
Antennae are flared! Trial excavations made here and there! Eventually, however,
the buried prize is recovered and then speedily thrust backwards into the
burrow, which is then sealed.
This would appear to be the end of this little saga and the scarab should now
be able to look forward to a bit of peace and quiet. However, rarely do things
go so smoothly in nature. Our hero, secure within his tunnel, is not quite as
alone as he or we might think. Firstly, even before the ball was first rolled
away from its construction site, a number of parasitic scuttle flies will have
sought out the scarab and attached themselves like glue to its elytra
(wingcases). During all the subsequent manouvering, including the crashes and
the tunnelling, these flies do not budge. However, within the darkness and
relatively humid surroundings of the tunnel, they will mate and lay eggs within
the beetle’s body. These will hatch into tiny maggots which will eat away at
the living beetle, growing and eventually dropping off to pupate within the
sand. A second group of unwanted guests were brought into the tunnel inside the
ball. These are smaller dung beetles of the genus Aphodius, the
cuckoos of the coprophagous world. How and why these relatively active beetles
contrive to get themselves incorporated into the scarab’s ball is not well
understood. Probably, the original habitat of these little beetles was in
surface dung but, since this dries very quickly in the Arabian climate, by
hopping into the scarab’s private supply they may gain the advantage of a less
quickly-drying food source, but without the hard work of buying it for
themselves. Some species of this genus in UK are true cuckoo parasites in the
breeding chambers of dor beetles (Geotrupes).
As already mentioned, the larger balls rolled away by scarabs are used to
provide food for larval development and are not eaten by the adults. The ball is
buried, as before, but probably to a greater depth. The female then cuts the
ball up into small pieces and remakes it into a pear-shaped mass, in the top of
which a single egg is laid. The mass will provide sufficient food for the whole
of the life period of the fat white ‘C’-shaped grub. Each female scarab lays
only about six eggs, each in a separate brood ball. This small number of
offspring for beetles such as S. cristatus which provide
specialized brood care is to be contrasted with the tens of thousands of eggs
laid opportunistically be female oil beetles, about which a future article is
planned.