A memorable month May 2004 in the USA

The year 2004 was really a year to remember. One of us (PJ) was there during spring time. He went through Canada to Washington, to be in the Smithsonian. In Fairfax, Virginia, he could see the emergence of millions of Magiacada septemdeam, the big 17 year US cicad, which, after seventeen years of larval life, spent underground feeding on the roots of trees, were coming out. They were emerging at the beginning of May in great numbers, but were not singing yet. Perhaps they were shy and busy in extending and drying their wings after leaving the pupal skin. The pupae, which were still awaiting adult emergence, were numerous around, on the trunks and at the foot of the trees. It is said that certain mammals, birds, amphibians and reptiles feed on them. Really, the feeders were quickly disgusted due to the abundance of food available. Some restaurants in Washington offered fried cicadas and had published attractive menus wherein those poor creatures were listed as the most original dish. I inferred that humans were the main predators of the cicadas.

This appearance of those poor cicads, totally inoffensive, do not resemble the Egyptian plagues or the Hitchcock birds. They were totally harmless. But daily newspapers were exaggerating a lot about their nuisance potential. It was the 1987 brood, which was coming out from the ground, and the period of their emergence was around one month or even less. That allowed those adults to dry in the sun. The males produced slowly their song, a rather discordant, a song which has tempted some composers, eagerly looking out for some novelty.

Happy are the cicadas, since their wives are mute, wrote one day some macho writer at the beginning of an entomology book. Yes, among the cicadas, only the males sing, or better screech to be more correct. They can all together produce sounds as strong as a subway train entering a station, or a child yelling, or working of a pneumatic drill. At 90 decibels, their song competes with a lawn mower. That is not at all exaggeration. People complained that in some golf clubs it was this year really deafening. The players could not hear each other to count their score. These cicadas are present in the District of Columbia in Washington, and in 15 eastern states of the USA. If their song is not really a love song, it is at least a mating call. The females are not completely mute. Well heated under the sun, they answer with a rattling of the wings. The rattling is an OK to the male singing.

As I said before, those insects are harmless, and it is only their eggs, laid in young branches, which can damage some of them. Sensitive journalists have strongly protested in Washington against children who remove their wings, throw them under the cars and torture them. This behaviour is alarming, and should be discouraged. La Fontaine, speaking of the youth, said that their age is merciless and Seneca used to say that the future cruelty of Nero was already visible when, as a child, he removed the wings of flies, still alive. Those journalists correctly proposed the denunciation of a "cicada abuse". Those creatures waited 17 years to get out of the soil. Should not people leave them alone and allow them to take the sun in peace?

Another American cicada, Magicicada tredecim, has a 13 year cycle. It is tempting to explain these strange cycles as being a means of self-defence against the predators. Evolution of such long life cycles, as also in case of cockchafers, seems to have the advantage of protection against a multivoltine predator. The pupa gets out of the soil only when the ground temperature reaches 17°C. During those 17 years beneath the ground surface there are 5 moults in the soil, near tree roots. The adults are expected to live for only 2 to 4 weeks outside, under the sun. Egg laying takes place within a small incision in tree branches. The eggs hatch on the twigs and the larvae drop to the ground beneath, and immediately enter the soil. A female deposits 400 eggs at an average.

It is said that, in the countryside in Serignan, France, Jean-Henri Fabre shot twice with a cannon to see if the cicadas would stop singing. It was in vain;

they did not stop. As Messiaen has imitated in his operas the bird songs, several American musicians tried to imitate the cicadas, without attaining the original harmony, if we can speak of harmony. Are the cicadas happy, when singing ? Probably they are, since this appearance under the sun, after having being jailed during 17 years, seems to take them to the peak of happiness, as if they have found again the lost paradise.

In May, says a French proverb, do what you like. I think I obeyed the proverb. May is probably in the United States, every 17 years, the cicada month, but it is also the season of love for the Limulus, those archaic and strange Arthropods, with blue blood, the famous haemocyanin, in which copper replaces iron, but which is dissolved in the serum and not incorporated into cells, like haemoglobin. Limulus are direct descendants of trilobites from the Palaeozoic. They also develop through a trilobite-like larva. They come directly from the Ordovician-Silurian junction, more than 450 million years ago. Limulus polyphemus or horseshoe crabs are, at spring time, pressed against each other, in the Mexican gulf, and the females, surrounded with their suitors, are laying eggs on the sandy beaches and are fertilized by aggressive males, which fight each other to achieve maximum fertilization. They are everywhere, but their number is certainly regressing, because they are hunted to be used as fish bait or to pump out their blood, which is believed to have a strong antibacterial property. New regulations ask the fishermen to release them to the sea after draining their blood. But, after this blood "donation" can they survive bacterial infections?

Limulus are everywhere along the Atlantic coast in the US. The Mexican gulf is a remnant of the Triassic Sea Tethys. Another genus and several species exist also in Indonesia and in Thailand-Vietnam-Japan, which are the other end of the palaeogeological Sea Tethys. They have been eradicated in the Mediterranean sea, because of the drying of the sea sometime at the end of the Tertiary. In Thailand people hunt the females to eat their eggs, which taste like caviar. Thai people eat even the big Belostoma, the aquatic bugs. They don't eat them entirely; they use only the glands of the male to produce a sauce, which tastes like bed-bugs, and is very much appreciated there. Killing the horseshoe crabs for a small number of eggs, from which they produce only a few grams of food, is a hopeless slaughter. That reminds one of the massacres by the Romans, killing the flamingoes by thousands, to eat their tongues. Mating among the Limulus are well synchronised and massive. Some young individuals mix with the others, and this phenomenon is not very well understood. Birds on the shore watch the females, so that they may later dig into sand to get their eggs. In spite of all this predation the species has managed to survive from such early days of animal evolution to this date.

A book has been recently written on these Arthropods in the US by Shuster et al. (2003). We should not forget that the horseshoe crabs descended directly from the trilobites and must have retained the same biology, since they have the trilobite larva. The trilobites have disappeared, and the horseshoe-crabs have survived. It is true that the recent discovery, of a living graptolite, a Notochordate, Cephalodiscus graptolitoides, in the ocean bed, near New-Caledonia and Norfolk island, shows that there is possibility of discovering some more forms, which at present seem extinct. Cephalodiscus dates much before Limulus and from a period close to the origin of life; almost at the Burgess shales!

And, looking at the seventeen year cicadas, at spring time, in Virginia, it was interesting to realise that again they will be seen in 2021. I had the rare luck to witness an extraordinary phenomenon. But looking at the horseshoe crabs on the Mexican gulf beaches, I got the feeling of going back in time, in the age of the trilobites, during the Palaeozoic. I thought that perhaps the trilobites also had blue blood, with copper oxide, when they had been laying eggs on the shores of the primitive Sea Tethys. Their eyes, supposedly made of calcite, as they are preserved in the fossils, were perhaps made of proteins similar to those of Limulus. I have always doubted this. Of course, their visual organs were very complicated, often with a double vision, in and above the water or inside the mud. Some others were practically blind. Those Silurian, or even Cambrian beaches, were still free from any vegetation, amphibians were to appear much later, over a mat of Cyanobacteria; the Stromatolithes, and progressively proto-green plants, like the Psilophytales grew their meagre stems, then later on, mosses, lycopods, horsetails etc. appeared. Fishes were then the dominant group, algae were numerous, amphibians started to diversify. The trilo-bites were laying eggs along quasi-desert shores and very probably behaved frenetically like the horseshoe crabs in heat. The ancestors of spiders, trigonotarbids appeared, and still later the terrestrial scorpions and, much later the first insects. Thus the horseshoe crab belongs to that ancient stock from which insects evolved.

Having seen Danaus plexippus (L.), the monarch, flying in the greenhouses of the Mc Guire Center for Lepidoptera, in Gainesville, FL, PJ had admired this magnificent realisation in the natural conditions of a tropical forest, reproduced in greenhouses, which allow exotic butterflies and even dragon-flies to fly about and live healthily. We hope that one day some severe cyclone will not take away the greenhouse and the butterflies to the kingdom of Oz. In that greenhouse, there are a stream, a water fall and all the grasses and trees, needed to feed the caterpillars. There are, of course, still unknown food for some beautiful butterfly larvae, as for Graphium weskei, from the mountains of New Guinea. To one of us (PJ), it is the most beautiful butterfly and he has seen hundreds of them along the streams in the mountains drinking water. Sedlacek, an entomologist, at Wau field station, told him one day that he saw a female laying eggs on a plant. He did not look carefully because he was going to Australia on leave the next day. He came back and could never find again the mysterious host-plant.

In the Gainesville greenhouse, it will be necessary to introduce mosquitoes, if we want to feed the Odonata, and if their larvae accept to multiply in a slightly chlorinated water! The local climatic conditions will permit, with a moderate ground heating, Morpho, Ornithoptera and Papilio, to survive with their caterpillars, on their original plants. It is the third butterfly greenhouse in Florida after the old one in Fort Lauderdale and the new one in Key West. A superb working tool for the scientists and a nice attraction for the tourists. The poor Danaus attempt aborted migrations against the screen, so strong is the effect of their migratory genes. Will they survive long in this condition? Jean-Michel Maes, an entomologist from Nicaragua, proposes to use Central American species of Danaus, the one which is non-migratory.

This greenhouse is partly what the scientists have attempted to do in creating their Biosphere II in the American desert, with more or less success. However here, in Gainesville, it is an ultrasophisticated butterfly greenhouse. We could compare that to the English experiment of the creation of an artificial jungle in the island of Ascension in the middle of Atlantic Ocean, a concept, which originated, in 1843, in the mind of the great Scottish botanist, Joseph Hooker and which has survived for more than 150 years. When Charles Darwin stopped in the island in July 1836, he described it as "entirely destitute of trees". Really he did not see one bush: Oldenlandia adscensionis, one African Rubiaceae, probably then already rare. Eighty years before, Peter Osbeck, a Swedish priest, described the island as "a heap of ruinous rocks", with a naked mountain in the middle. The volcanic island is only one million years old and, as it has a tropical and potentially humid climate, it was covered rapidly after 1845 with a heteroclite jungle, coming from the whole of the tropical world from Argentina, to the Cape Province, and Australia, up to Norfolk island to the East. Kew Gardens and the Navy, following Hooker's advice, contributed to that flora enrichment with importation of hundreds of seeds and tropical trees, such as guava, banana, ginger, Opuntia, bamboos, Clerodendrum, Malagasy periwinkle, Cataranthus (Vinca) roseus, Australian eucalyptus, and Norfolk Araucaria. They all found the surroundings suited to them, and multiplied rapidly. Contrary to all expectations and contrary to ecologists' predictions, that "genesis" of a tropical flora in miniature was a total success. There are actually beetles, butterflies and caterpillars, coming from nowhere, in that pot-pourri of the jungle, totally man-made and the experiment goes on. As we are far in Ascension from any land and in the middle of Atlantic Ocean, any contamination is prevented. The island discovered in 1501, was still unhabited in the middle of 18th century and now it harbours nearly 1,100 inhabitants. Situated at 2,000 km from the nearest continent, the island has a basic limited flora of around 20-30 vascular plant species, of which about 10 are endemic. Most of the ferns have survived, only 4 are extinct and 5 are actually endangered. The Green mountain, the actual name of the formerly bare rock, has provided rain and prosperity. A new biotope, a mountainous, man-made, tropical forest was born and functions perfectly. It is a unique experiment, based on seeds from the whole world and chosen at random. That concept, Hooker created, has survived to the great displeasure of the ecologists and theoreticians. Hooker knew exactly what he was doing, because he wrote: "the consequences to the native vegetation of the Peak will, I fear, be fatal, and especially to the rich carpet of ferns that clothed the top of the mountain when I visited it". After all, the Navy saw greater benefit in improving rainfall and encouraging more prolific vegetation. The effect on the native vegetation finally was not so great.

A fascinating experiment in a natural landscape was done in Ascension island and is more enriching than what the Gainesville beautiful greenhouse has achieved. It would be interesting now to introduce in Ascension, since the experiment has been irreversibly made: Ornithoptera, Morpho, Papilio, Agrias, Urania and related, and their host-plants. Why not also try Timarcha spp., dear to one of us (PJ); there are some living in a similar climate and Galium, the host plant of Timarcha, grows anywhere. The evolution of this artificial biotope would be fascinating to study.

References

Schuster, C. N., Barlow, R. B. and Brockmann, H. J. 2003. The American Horseshoe

Crab. Harvard University Press, Cambridge, MA. 439 pp. Wilkinson, D. M. 2004. The parable of Green Mountain: Ascension Island, ecosystem construction and ecological fitting. Journal of Biogeography. 31: 1-4.

— Fig. 20.1. A-F: Various stages of Magicicada septemdecim, in May 2004 in Fairfax, CA, USA. The nymphs are coming out and the adults are just freshly ecloded from the pupal skin (photos Jolivet).

— Fig. 20.2. A: Limuluspolyphemus taking to water; B: Limuluspolyphemus in copula; C: Limulus polyphemus covered with barnacles; D: Brown pelican, Pelicanus occidentalis, on the shore. (All photos by Jolivet in Cedar key, Florida, USA, May 2004).

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