DISAPPEARING ACTS
nature’s camoflage artists
Text and pictures by Marijcke Jongbloed
It was a short time after my arrival in Arabia,
about ten years ago, that I first became interested in the wonderful insects
and arachnids of this area. Next to the hospital where I worked was a drip-irrigated
plantation of ornamental trees and shrubs. Between the regimental rows
of cultivated plants a wide variety of weeds and grasses grew. In a small
patch of ground, not more than 200 square metres in area, I eventually
discovered over 60 species of plants, some of which I have not seen anywhere
else since then. It was while taking photographs of these wild plants and
their seeds that I came across the insects that thrived in this unusually
verdant habitat.
Disappearing Moth
One of the first to attract my attention was a tiny day-flying
moth that appeared to be white as it fluttered from plant to plant. I was
keen to photograph it but every time it settled down it seemed to disappear
in front of my eyes. Each time that I approached the place where it had
apparently dissolved into thin air it magically reappeared, taking off
again from its sandy or grassy perch with its conspicuous fluttering white
wings. It took many hours of patience, not to mention several litres of
perspiration, before I had the pictures that I had set out to take. To
my surprise it transpired that the moth was in fact strongly coloured with
red and black polka dots on a white background. Such an apparently conspicuous
pattern hardly seemed to be a good basis for the magnificent camouflage
had almost thwarted my photographic efforts. Surprisingly however, when
this moth sits on sand it becomes well nigh invisible since the pattern
of dots break up the outline of the insect, rendering it virtually impossible
to distinguish until it moves.
A few months later I found the caterpillars of this extraordinary moth
(Utetheisa pulchella) on a Crotalaria bush, and they had the same basic
coloration as the parental form described above. However, in the case of
the caterpillar, the colouring did not function as a form of camouflage.
In fact, the caterpillars were so blatantly obvious among the green branches
that I suspect that the bright colours served as warning coloration, suggesting
to potential predators that they were either poisonous or foul-tasting.
Twig or Stick
Stick insects, members of the order Phasmida, were also well
represented in my lunch-time recreation area. In fact, I had never seen
a stick insect in the wild until I found one there. Since that early encounter
I have come across three or more different species of stick insects in
the Emirates.
A very common, but always fascinating insect is the towerhead grasshopper
(Truxalis procera). With its green and straw coloured limbs it is amazingly
hard to see when it hides in vegetation. There is another variety of this
insect – it is beige over its entire body, without any green parts. It
may prefer sandy or stony areas where its colour form blends with the background.
Magnificent
Mantis
Among the mantises there are many more examples of excellent
camouflage. The very colourful striped mantis (Blepharopsis mendica) which
is so easy to see when it sits on a rock, disappears completely when hiding
among the branches of a Euphorbia bush. The tiny fairy mantis (Oxyothespis
nilotica) has another advantage: it is so small that you can only really
see it through the macro lens of a camera or with the aid of a magnifying
glass. Of all the mantis species however my favourite one has so far eluded
efforts at identification. The first time I saw it was on a Tamarix tree
so I named it the “Tamarix mantis”. Its camouflage worked so
well that I did not even realise that I had photographed it until my film
was developed! Having not focused directly on the extraordinary insect
it does not feature prominently on the resulting slide, but the picture
serves perfectly to illustrate how closely it resembles a spray of tamarisk
flowers!
Predators like mantises use their camouflage for two purposes: protection
against predators and disguise against their own prey. This is also the
case with the two large insect predators of the wadis: the giant water
bug (Lethocerus niloticus) and the water scorpion (Laccotrephes fabricii).
On numerous occasions I have encountered a pond within a wadi which, on
first investigation, seemed to be devoid of animal life. One only had to
sit down quietly however and to wait patiently for a few minutes before
the water seemed to become alive. First the fishes start to emerge from
below overhanging rocks or grasses, then the backswimmers and whirligigs
resume their frantic surface activities. Next a large leaf floats by –
but if you try to pick it up it bites! At least, this is the case if it
is the giant water bug – I have no records of biting water scorpions as
yet.
Spiders:
Masters of Camouflage
The masters of camouflage however are the spiders. Every summer
the sunflowers in my garden are host to a small yellow crab spider. During
the first year my encounters were all accidental but now that I know what
to look for I can find it quite easily. I have frequently observed it as
it lies in wait for bees to visit the flowers. Despite the fact that the
bees are four times its size it kills them easily and drags them to the
underside of the flowers where it feasts on its prey’s body fluids. The
male crab spider, speckled brown in colour, is even smaller than the female,
not more than two millimetres in diameter and it apparently has a different
hunting strategy. The easiest time to distinguish these strange spiders
is during their mating behaviour when the darker coloured male is astride
the yellow camouflaged female’s back. One conundrum which I have not yet
solved is what happens to these sunflower inhabiting spiders when the sunflowers
in my garden are no longer in flower?
The absolute master of camouflage that I have ever encountered was discovered
hiding under a piece of plywood lying on the sand. As usual, when we are
looking for hidden creatures, we turned over the plywood and immediately
a spider scuttled away. If it had not moved we would never have seen it.
Its speckled body and legs had the exact same colours as the grains of
sand on which it rested. Later, I regretted that I had not taken another
photograph after placing the spider on a contrasting background. It would
have been interesting to see precisely with what colours and patterns its
exquisite camouflage was achieved.
Startling
Blue Eyes
Even relatively large insects such as the huge caterpillar of
the oleander hawk moth can be difficult to detect among the leaves of their
host plants. It is only when one discovers the damage done to carefully
cultivated shrubs that the search begins for the culprit. And when you
find it, and marvel at its delicate beauty, it is easier to forgive its
sins. Potential predators other than aesthetically sensitive humans, such
as birds for example, are met with a sharp display of warning coloration
if they venture too close. Even when you know what to expect the sudden
appearance of enormous eyes and the split second transformation of a peacefully
munching long caterpillar into a scrunched up green ball with huge staring
blue eyes is startling.
As long as there are plants to study, I shall enjoy the insect side-show
for its rare beauty and fascinating variety.