Living Clouds

In 1955, when PJ arrived for the first time in Zaire or People's Republic of Congo, formerly the Belgian Congo, to conduct an entomological and parasitological mission in Kivu and Ruwenzori, he spent one month near the Semliki falls, the outlet of lake Edward and one of the sources of the Nile. Those lakes, Edward, Albert, Kivu, Tanganyika, Rudolf etc., have changed names several times according to the dictators reigning in the surrounding countries. Lake Edward has been named for some time as the lake Idi Amin Dada, and lake Albert as the lake Mobutu Sese Seko. They are going to change again following the vicissitudes of politics, and here I prefer to use the older names. All those lakes are pretty different from each other, including the rest of Ethiopian lakes, and they are situated in the earthquake zone in the middle of the Rift valley. PJ has also visited lake Rudolf (now lake Turkana), during an expedition in helicopter along Omo valley, in the period of a yellow fever epidemy, and went to the Koobi Fora park, an extraordinarily area rich in Pliocene fossils (the elephant cemetery of Jeannel!), located along the northern shore of the lake. This area is situated on the border of Kenya-Ethiopia. During this expedition, PJ was once left alone awaiting the next helicopter in an isolated village surrounded by the natives armed with spades and bows. Few hours passed with the villagers speaking no known language and PJ leaning against a big tree. At the end, PJ, a bit disorientated and also not much reassured, remembered Hollywood films and was questioning himself if he will be put in the cooking pot or crowned king of the tribe. Finally the helicopter came and PJ could come back to the camp at his great relief. All those lakes have some peculiarities and some are well known for the sudden hatching of millions of tiny Diptera. Lake Shala in Ethiopia or lake Nakuru in Kenya is covered with pink flamingoes. Others (lake Langano) carry often balls of blue algae (cyanobacteria), floating on the suface; many are frequented by hippos and crocodiles. Hot springs are frequent in all those areas. In some lakes, Gondar, Margherita or Zwai lakes, people use boats made of entangled reeds, as in Egyptian times; also there cows are sent to swim to reach islands. Let us recall that similar reed boats are used also in Titicaca lake in Bolivia. Populations there are rather primitive and hardly touched by civilisation, specially around lake Rudolf or lake Margharita. In many places, during that period, they never heard of the emperor Haile Selassie, at that time the lord of Ethiopia, the king of kings and their direct ruler (Jolivet, 1991).

Between the lake Edward and the lake Albert, the Ruwenzori chain of mountains rises, of which a summit, the Peak Margherita, reaches the height of 5118 m. That chain was named by the ancients as the mountains of the Moon. "The mountains of the Moon feed with their snow the sources of the Nile", wrote, in the third century AD, Ptolemaeus, the pioneer geographer. Remember that around the year 60 AD, Nero sent an expedition to report about the local tribes, their wealth and the origin of the Nile (Cloudsley-Thompson, 1994). Seneca and Plinius the Elder wrote something about the expedition. It is not clear if they were looking for the sources of the Blue Nile or the White Nile. On the way down, on their road, in Sudan, the old Greco-Egyptian civilisations existed, the ruins of which have been left as remains of several temples, Roman baths and hundred of pyramids, and the place is easily accessible by train (Shendi and Meroe). The local writing has not yet been completely deciphered. There was the kingdom of the Candaces, the meroitic civilization, running in parallel with Axum civilisation in Ethiopia. There ruled the Amazon queens, mentioned in the Bible.

It is certain that the Rift valley big lakes, as also the Ruwenzori mountains, have a part of responsibility in the birth of the Nile (White Nile), as has lake Gondar in Ethiopia for the Blue Nile. The Ruwenzori glaciers and snow surely feed the Nile, and in 1954 PJ climbed the mountain and stayed there one month studying insect biology and parasitology. Both White and Blue Niles meet in Khartoum (in the old times Soba) and Nero legions passed through this region while going south in their adventurous mission. When the mission returned, Nero decided that to face the ferocious nilotic populations was not worth the conquest.

In Ishango, a stop-over near the Semliki falls and near Edward lake, PJ met the German zoologist Bernhard Grzimek who was making a film with his son and a cameraman. They were working for the famous film "No room for the wild beasts", which proved greatly successful. Gzimek was then director of the Frankfurt Zoo. He lost his son several years later in a plane accident over the Ngorongoro crater, when filming there rhinos, hyenas, antelopes and lions. On the volcano side, Gzimek planted a plane propeller over his son's tomb and wrote: "He liked so much the wild beasts that he gave his life for them".

In Ishango, hippopotami roamed by the hundreds; they were so numerous and dense in their population that from time to time huge epidemics of anthrax decimated quite a lot of them. The beasts used to give furious head blows against the visitor's boats. Birds were numerous and varied. Elephants and lions used to come by day or night to visit the camp. But during the night, groaning of the hippos and roar of the lions dominated all other noises.

There happened almost every morning a strange phenomenon over the lake; a black cloud used to appear suddenly emerging directly from the water surface. One day we found the key to the mystery. The cloud appeared near us and we were surrounded by millions of non-biting mosquitoes, an explosive mixture of chironomids, chaoborids, and several others. The chironomids were the dominant species in the cloud. The lake was polluted by hippo excreta and was exactly what we define as an eutrophic lake, where mostly chironomids or blue algae enormously multiplied.

Blue green algae, Cyanophyceae or Myxophyceae, now named Cyanobac-teria, multiply easily in small ponds or lakes, and even in the sea, when the water is heavily polluted by nitrates. Those cyanobacteria, like Microcystis, can be heavily toxic and recently in New Zealand calves and cows died near a reservoir covered with those water-flowers (Wasser-Blüten). Red sea gets its name from that rare phenomenon, and the same happens quite often in the California gulf. Generally farmers are responsible for pollution with excess of nitrates or animal excreta. Intensive agriculture has its drawbacks.

Mosquito clouds are a rather common phenomenon, not only in the Rift valley lakes, but also in Central America, as in Nicaragua. Let us note also that Lake Nicaragua, now heavily polluted, was a place for freshwater sharks and sawfishes. Freshwater sharks are also met with in central New-Guinea in the Murray lake, in the Mindoro lake in Philippines, and in the Maracaibo lake in Venezuela. Sawfishes are also found in the Murray lake. In that last lake, as in the Nicaragua lake, sea fishes probably came through the rivers. As regards the Mindoro, it was a gulf, which was closed accidentally.

The inconvenience, caused by those minute mosquito clouds, is that they penetrate into the nose, the eyes, the ears... and glasses of wine of the customers of the restaurants along Languedoc-Roussillon coast, near Montpellier. Tourists and locals often complained about it. However, those tiny insects do not bite, do not transmit diseases and are totally harmless in those respects. Of course, people may complain about a few stinging chironomids. But such chironomids are extremely rare, and they are really living fossils in South Africa. Most of the 5000 existing species of chironomids suck nectar of flowers, or generally do not eat at all in the adult stage.

Are the chironomids really pests? Let us consider the examples of various localities, viz. Sudan in Khartoum, Nicaragua lake in Nicaragua and the Languedoc ponds in Languedoc, near Montpellier in France.

PJ was in Khartoum in 1963 when Walker started his study of chironomids. In Sudan, the populations of the midges reach their maximum from November to May, during what we could name as winter, even if there the temperature is rarely below 20°C. Enormous masses of insects, which are named there nimitti, makes life almost impossible to the populations living along the Nile and more specially to the hotel customers or the civil servants of the ministries. Rightly or wrongly the midges are accused for all sins of Israel. Serious allergic reactions are attributed to them. The midges penetrate up to 300 m beyond the river shore, and it happens that people quit their houses and once it was necessary to evacuate a hospital. Reactions are mostly neurotic, but people always confuse midges with biting mosquitoes. People even thought about building a new capital away from its actual place. This capital was built in the past by Gordon and improved later on by Kitchener. Gordon built it using the British flag as a plan for the distribution of the streets. Since 1956, a lot of literature has appeared on the midge topic in Sudan. The Nile here plays the role of an eutrophic lake with Chironomus and not of an oligotrophic lake with Tanytarsus, though that genus is also abundant there. One may explain the dam phenomenon as due the confluence of both the Niles, the Blue and the White, in Khartoum, and also due to many artificial reservoirs created here and there around. The gardens bordering the river are also used for resting by the adult midges. That kind of shelter did not exist in the past, when the country was a plain desert.

In Nicaragua, in 1962, a layer of decomposed midge adults was found having more than one meter of depth. Such accumulations, however more modest, were found in California and on the littoral parts of Languedoc in France. In Carnon, near Montpellier, a layer of more than 30 cm of dead midges once was found around shops.

The chironomids have the defect to provide basis for formation of enormous populations of spiders, which may invade houses, when looking

— Fig. 16.1. A: Chironomus salinarius Kieffer, male adult and larva. B : Cricetopus vitripennis halophilus Kieffer, adult and larva. Both chironomids live mainly in semi-brackish water (after Jolivet, 1991).

— Fig. 16.1. A: Chironomus salinarius Kieffer, male adult and larva. B : Cricetopus vitripennis halophilus Kieffer, adult and larva. Both chironomids live mainly in semi-brackish water (after Jolivet, 1991).

for their preys. When they are small the midges penetrate more easily inside the dwellings through doors and mosquito nets, and may enter eyes. We have already mentioned that in the seaside resorts, in summer time, chironomids invade in the evening the restaurants, dropping into the glasses and dishes. That raises some problems even if it is more psychological than hygienic, but all the customers are not necessarily entomologists and do not realize that the midges are clean, harmless and do not carry diseases.

In the Languedoc area, two midges predominate: one Chironomus with red larvae and a Cricetopus with green larvae. They are much more difficult to control than the mosquitoes. However, the chironomids, in equilibrium with the local fauna, are a blessing for the environment. They feed the fishes and the birds and bats. They become a pest only when they multiply very rapidly. People tried to contain them by different ways, by mechanical control, biological control, but mostly by chemical means against the adults using the organophosporic insecticides. Success is rare and the insecticides are polluters. Some success was obtained with integrated control, mainly in South Africa.

It seems that chironomids are attracted by certain sounds, the human voice vibrations, certain degrees of luminosity and heat, CO2, etc. Maybe it is a remnant of their old state of biting mosquitoes and blood suckers at a certain stage of evolution. To develop physical or chemical lure seems to be a relic of the past. Planning a biological control, when they are so numerous, is only a wishful thinking, nothing more.

Finally, the treatment of the chironomidophobia is also matter of education to the population, as the midges are totally harmless. Fight against pollution is also a factor, which should not be ignored, as the midges help reestablish the fragile biological equilibrium, and this balance would be disrupted, if midge population is made to decline through human efforts. Also one must not modify too much the food chains in water and in the air by an irresponsible use of insecticides.

The chironomids are not the only insect clouds to cause nuisances. Clouds of Phryganes, Ephemeroptera, Homoptera (such as Nephotettix, so abundant during the typhoons in Hong Kong), Blepharoceridae Diptera or nuptial flights of ants and termites, all may be nuisance makers , mostly in the tropics.

Let us talk a bit about Nephotettix They are Homoptera, small version of the cicads, which hatch in mass in rice fields and invade shops in Hong Kong. They are normally sap suckers, but it happens that they often try to sting and even they are able to remove a bit of blood. PJ has beeen attacked many times, after the rainy season in Ogaden (eastern Ethiopia) by herds of those small insects. They tried to bite like mosquitoes. A very tiny Homoptera, Orosius celluhsus, vector of cotton phyllody, a mycoplasma affecting the cotton flowers, in West Africa, has been described, in India as "biting man".

All those small insects are just small nuisances. They do not transmit any disease, and, after all, they are sometimes signs of nature fighting pollution.

References

Cloudsley-Thompson, J. 1994. The Nile Quest. The Longdunn Press Ltd., Bristol, U. K.

Jolivet, P. 1991. Curiosités Entomologiques. Chabaud publs., Paris.

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