Two curious students students make et's resident naturalist hit the books
By Richard Hoath
I had the great pleasure of giving a series of talks at the Maadi Community School last month, talks on Egypt’s wildlife to students ages 5-14. It was wonderful. In a school that embraced nature and natural history, I found myself addressing audiences of engaged and interested young people. But my young audience saved their best til last. At the very end, a brace of the youngest children who I had spoken to earlier, came up to me with a precious package. As they delicately unfolded the tissue paper, the contents of said package became clear. It was a dead wasp.
I doubt whether a dead wasp has caused so much curiosity or joy before. The curiosity was that of the two children. They had participated in my talk, found this sadly deceased creature in the school playground and wondered what it was and why it was like it was. The joy was mine. I flashed back many decades to my own curiosity about the natural world at a similar age. I hope, like me, that the two young naturalists never, ever lose that fascination with the natural world.
It was an Oriental Hornet Vespa orientalis, a large, spectacular species of wasp common throughout much of Egypt, away from the true desert. The female queen approaches 4cm in length, while males and workers are rather smaller. It is strikingly patterned in deep purplish, chocolate brown and yellow, the yellow on the face and on a broad band across the abdomen. Like all wasps it has a very narrow connective process between the thorax and the abdomen, a feature that has worked its way into the fashion industry through the descriptor “wasp-waist.” Even supermodels would struggle to have a connective process as narrow and slender as the Oriental Hornet. And it has two pairs of wings, the forewings marked by a chestnut leading edge.
The question I was asked was why was the wasp patterned like this? And like many questions from curious young children, it was an extremely good question.
The immediate answer is that the Oriental Hornet is colored and patterned so dramatically because it is potentially dangerous prey for any predator. Like many bees and wasps, it carries a sting in its tail or rather abdomen. As anyone who has been stung by a bee or wasp will know, this is painful. I was once stung by a bee species twice in a single tennis game and was so thoroughly distracted by trying to identify my assailants that I lost. And humans are very big compared with the normal predators of these insects for which that sting is potentially lethal. So the loud dark and yellow patterning of the Oriental Hornet is like a big banner saying “Don’t mess with me – I’m dangerous.”
It is a common strategy in the natural world and especially amongst the insects. Egypt’s most striking butterfly species – arguably – the Plain Tiger Danaus chrysippus is strikingly patterned in orange, black and white. It is a large butterfly with a wingspan of nearly 8cm and bears a very close resemblance to the North American Monarch or Milkweed butterfly.
It might seem to be suicidally brash for an insect of this size to advertise itself so brazenly. But it does so in the confidence that it is virtually inedible, the toxins absorbed from its caterpillar days spent munching on poisonous food plants rendering it very distasteful as an adult. The Plain Tiger is resident throughout Egypt outside the desert areas, though being also migratory can turn up anywhere. It is also very territorial. I can remember being mobbed by a particularly belligerent Plain Tiger in the Democratic Republic of Congo as I was climbing Mount Goma.
Things get a bit more complex thereafter. There is another species of butterfly found in Egypt, the Diadem Hypolimnas misippus. The male Diadem is a very distinctive butterfly, a tad larger than the Plain Tiger but very different in appearance. He is a rich velvet black above with two large white spots on each forewing and one on each hindwing, each subtly surrounded by purple. He cannot be mistaken for any other butterfly species in Egypt.
The female Diadem is very different. She is orange, black and white — in fact barely distinguishable in the field from the Plain Tiger. The only really discernible difference between the female Diadem and either sex of the Plain Tiger is that the former lacks any black spots on the all orange hindwing.
This is clever! This is sheer bluff. The Diadem is not toxic. In insect terms it is probably quite tasty. But in mimicking the Plain Tiger, the female Diadem sends the same warning signals to potential predators as the toxic species. The trick only works if the bluffer is much less numerous than the bluffee. And in Egypt that certainly seems the case with the Diadem limited to only the north and south of the Nile Valley and Gebel Elba in the southeast.
Returning to the Oriental Hornet, the startling coloration would seem to be a warning to those in search of a meal that this is a rather unpleasant and dangerous meal. That said, it does get eaten. The bee-eaters, spectacularly colorful birds, are as the name suggests eaters of bees and of wasps. They are not deterred by the warning coloration and nor by the stings.
Come April, the European Bee-eaters will be passing through Egypt all resplendent in chestnut and turquoise and yellow and black. They will be passing over central Cairo, even in my neighborhood of Garden City, and the air will be filled with their calls, a sonorous kroo, kroo, kroo. And they will be hawking for hornets over the mango trees that shade my balcony. But bee-eaters are careful. They take the hornets in flight in tweezer-like slender bills and then head for a perch, a telegraph wire or satellite dish. They then beat the hornet against the perch to get rid of the sting and dine on the de-toxed wasp. So against the bee-eaters the warning coloration does not seem to be — or bee — that effective.
But there may just be another purpose behind the vivid yellow banding of the Oriental Hornet. In 2010, a paper was published in Naturwissenscaften by Dr. Marian Plotkin of Tel Aviv University with a team of Israeli and British colleagues. They were curious as to why the Oriental Hornet flew during the heat of the day rather than, as with most wasp species, in the early morning. Previous work by the late Professor Jacob Ishay had suggested that the wasps could actually use solar radiation as a source of energy.
Dr. Plotkin found that the physical structure of the yellow band across the abdomen of the Oriental Hornet differed from the structure of the dark brown parts of the hornet’s body. The structure of the yellow segments enabled the hard cuticle to trap the light and the distinct pigment within the yellow cuticle, xanthopterin, was actually able to “harvest” the energy from that light. The Oriental Hornet was, in effect, solar-powered.
Whether this is a good or a bad thing from the perspective of the Oriental Hornet might be open to discussion. By coming out in the heat of the day they may be able to exploit food sources that earlier in the day they might have had to compete for. But in spring the bee-eaters are making hay as they sweep and swoop over the mangos and thrash and bash the stings out of their waspish prey before they dine.
But I would never have found this last research had it not been for two very curious young naturalists who found a dead wasp and wondered just why it looked as it did. I thank them very, very much! et