Interesting ways of bees and dung beetles

It is well known now, through Jean-Henri Fabre's observations, that many Hymenoptera hunt spiders, caterpillars, locusts and grasshoppers, which they paralyse with their sting to feed their offspring. The paralysed prey remains fresh and without any rot for a long period. This preservation of the prey, which is in a state of prolonged coma, is a primitive substitute of the modern refrigeration. The honey bees (Apis melifera) amass honey, which they collect and produce from the nectar and pollen harvested from flowers. Honey with pollen is used to feed the larvae and the adults in their colony, and, according to the quality of the food, larvae will become workers or queens. The honey includes the worker bee's saliva, which has preservative quality. Hence the honey remains free from fermentation and decay indefinitely. The larva, which is meant to develop into a queen, gets a special food richer in proteins, the royal jelly, secreted by labial glands. Sex is mostly determined by the number of chromosomes, males or drones being haploid, i.e. having half of the number of chromosomes in the females, which may be sterile workers or egg laying queens.

There are in the tropics, small bees (Meipona and Trigona) which produce excellent honey, and they are stingless, but are often aggressive for their defence.

In Brazil, some Trigona bees come in groups over your hairs, and try to bite the scalp. Others surround the intruders with a buzzing cloud to thus create fear, but there are also, among the species of this genus, some very sweet bees, which never attack. PJ remembers, in Burkina Fasso, near a river, when using lemon grass as a mosquito repellent (phthalates and other repellents were not available on the spot), he could escape mosquito bite, but he was surrounded by clouds of Melipona. Repulsive to mosquitoes, the lemon grass juice was strongly attractive for the stingless bees.

Why Trigona bees were attacking the hairy surface? The British naturalist and traveller, Thomas Belt, reporting his experience in Nicaragua, wrote that it was because the bees had the habit to attack the furry mammals, mainly the sloth. It is also likely that bears, which are fond of honey, may also be a potential enemy of the bees. The bees may also be attacking in Africa hairy apes. As these bees are stingless and having no other means of defence, they take to biting. In Vigosa University, in the state of Minas Gerais, in Brazil, there is a round laboratory for apiculture and meliponiculture with a good number of wild bee hives around. They are free to gather pollen outside, but their nests are visible through a glass in case of each of their hives. The nests are of different species. Outside, there are also hives of the Africanized honeybee, so it is called there. There, if as you get close to a hive, the bees suddenly start emitting a buzzing noise, and appear agitated, and a prompt retreat from the hive becomes necessary. PJ with a team of students, once in Ethiopia, in the Ogaden, was suddenly followed by angry African bees. They were trying to bite, and he was protecting his eyes, but the insects were coming over his hairs from everywhere. Obviously his scalp, covered with hairs, was attractive to them, and he (PJ) was running away, trying to crush the insects over his head. The pursuit lasted after few hundred meters. One of his colleagues, in Zaire, was bitten over the head by an enormous wasp, and went into coma. He got out of it one month later, 90% disabled. He was constantly shaking, since the wasp had probably bitten a vital centre of the brain. Attraction for hairy surfaces seems general among these Hymenoptera, though some wasps mainly aim at the eyes. PJ has still the bitter souvenir of a wasp bite on the upper eyelid, when as a teenager he was trying to displace a wasps' nest. Thank God he was not allergic to the sting poison, and the bite resulted only in an enormous swelling. A classic case is that of the German naturalist, Fassl, who died of malaria in 1922. He was hunting for butterflies in Amazonia, when he was stung into the eye by an enormous wasp. He spent 8 hours in terrible pain, before succeeding to remove the sting.

To come back to Trigona bees, another peculiarity of these insects is that, when they feel a danger approaching their hive, they arrange themselves in a circular group around the entrance of the hive. It is what we have named cycloalexy (see the chapter on "Round defence"). Only in Viçosa University, you can observe them in semi-freedom in a wonderfully equipped laboratory. Beekeeping with Trigona and Melipona in Mexico and in South America declined rapidly with the invasion of the African variety of honey bee.

Most of the bees collect pollen from the stamens of flowers, squeeze them into special pollen baskets located on the tibiae of their legs. In East Africa (Ethiopia, Sudan, Kenya), some races of Apis mellifera steal smelly flours, instead of pollen in village markets. They like most of all shirro flour, Cicer arietiinum or chickpea. What is strange is that those bees, so aggressive when you approach their hives, do not bite when you take the flour in your hands to transfer it into bags. When disturbed, they go away to come back immediately, exactly as do the flies when chased out from a pot of jam. Under that situation the terrible bees are peaceful.

Von Frisch wrote to one of us (PJ) in 1963 that European bees collect sometimes any pulverised substance, like brick or coal powder. It is evident that the nutritive value of these substances is nil, and one may consider this behaviour as a mistaken instinct

It must be noted that the purple emperor, Apatura iris, the beautiful European butterfly, sucks humid bricks or even humidifies the brick with its excreta before sucking with its proboscis. It seems that the male sucks this way to get sodium, potassium, and calcium present in the brick to be used in making its spermatophores, and used by the female in egg making. It is also possible that Von Frisch's bees get calcium with the brick dust.

Melipona and Trigona are known to collect enormous quantities of pollen and their stock cells in the hive are full of almost pure pollen. To feed their larvae with pollen and honey is the normal method for the 400 known species of these small bees. In Mexico and in Guyana, they pollinate well vanilla. In the areas, where they are absent, the pollination has to be done by hand, a method, which was learnt through a fortunate discovery by a slave, named Albius, in La Réunion. Outside Mexico, in the Mascareignes, New Caledonia, and Madagascar this method is now commonly used. Let us add also that Trigona males participate nest building and in defence of the hive, a rare situation among honey bees, as in almost all bees these activities are confined to sterile females or workers.

It must be said that, though melipones and Trigona are excellent pollinators, they often perforate flower's corolla, as do the bumble bees and carpenter bees (Xylocopd) and then go straight to the nectaries. Like the honey bee, those small insects use also cochineal dew, sugar from extrafloral nectaries, smashed fruits, and collect sap and resin, which exude from buds and stems. For a long time people were surprised to find some Trigona resting upon the putrefying cadavers, animal excreta and bird droppings. Then one day entomologists discovered that some species of these bees are partially or totally necrophagous (Roubik, 1982), that is feeding on dead and decaying matter. Roubik (1992) mentions that those carrion feeders shun animals that have been dead for more than a brief period or are infested with fly larvae. They efficiently collect new carrions, which they convert into a greenish grey pasty mass, adding their saliva. The pasty material is then stored and used as though it were pollen. This substance has lower energy than pollen, but is richer in protein.

In Amazonia there are no Nerophora beetles, as in temperate areas. Those big beetles, yellow and black, practice a family life and carry and bury cadavers of their dead. There feeding on cadavers is practiced by big dung beetles, the Phaneus, and wild bees like Trigona and also the ants of the genus Crematogaster. At least three species of Trigona are entirely necrophagous: T. rassipes, T. nerophaga and T. hypogea. Among these species, the pollen baskets remain vestigial or small and ill developed, since they collect only putrefying flesh together with monkey excreta. A mixture of honey-excreta-cadavers does not seemed very attractive, but honey, if they collect some, and predigested flesh are separated for storage into different cells in the hive. No pollen is found in either store. It may be added that Lestremelitta, obligate robbers of food from nests of other stingless bees, are totally unable to gather pollen from flowers because they have short mouth parts and regressed pollen baskets. To survive they plunder the pollen reserves from the hives of those species of Trigona, which collect it. As among parasitic ants, those social parasitic bees are closely related to the species they plunder.

Roubik (1982) studied in detail the biology of the necrophagous bee, Trigona hypogea, in Panama. Cadavers of monkeys, snakes, lizards, toads, fishes and even of big insects are foraged, used as a source of proteins, digested and regurgitated to other individuals (trophallaxy), when the bees go back to the nest. To dismember the cadavers, the Trigona bees possess toothed mandibles, specially adapted to tearing. They communicate with their partners using pheromones, smelling molecules, used by many insects as a kind of chemical language. The foraged material is stocked as partially digested flesh. The stored material is fermented by bacteria. Those bees are extremely aggressive towards flies, which are tempted to lay eggs on the cadavers.

Another peculiarity of Trigona bees is that around 23 species live inside termite nests and at least five species in ant nests. The association is peculiar and not adequately understood, and these small bees are well tolerated by the termites, and by the ants, which do not seem to get any reward out of the association. This phenomenon is mostly known from tropical America and Malaysia.

The specific behaviour of the necrophagous bees has never been found in the tropics of the old world. It is also true that the Amazonian forests harbour many other extraordinary events. I just mentioned Phaneus and other dung beetles, which instead of collecting excreta are necrophagous. We find there, in the canopy of forests, some coprophagous beetles, e.g. some species of Canthon, which collect exclusively monkey droppings. Those dung beetles make a ball with the excreta, as our land dwelling ones do, then they, attached to their ball, drop to the ground and drive this ball into the forest soil some dozen meters away. PJ walking in Barro Colorado island in Panama in the morning was always wearing a hat, since the beetles started to drop their excreta balls from the trees at 9.30 am and you could find your head covered quickly with balls of monkey feces. It is surprising that people have just started studying biology of these canopy dwelling dung beetles. There are also phytophagous dung beetles in Australia and also there are coprophagous weevils. Really it is a world upside down there!

References

Jolivet, P. 1991. Curiosités Entomologiques. Chabaud publ., Paris. Roubik, D. 1982. Obligate necrophagy in a social bee. Science 217: 1059-1060. Roubik, D. 1992. Ecology and Natural History of Tropical Bees. Cambridge University Press, Cambridge,U.K.

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