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biodiversity

biodiversity

Membracidae: Wonder of

Membracidae: Wonder of terrestrial biodiversity. The astonishing biodiversity of our planet is the result of a perpetual and never-ended evolution where the biological species had to adapt to an often hostile environment. The complex relationship between them and their habitat, the pressure of the natural selection and the spontaneous mutations, between chance and necessity, shaped living it in a multitude of forms, which exceed our imaginary. If all the mechanisms of this evolutionary process are not completely elucidated, it will be sure that the dynamics of the life has transformed, eliminated and modified the species since the beginning of time. A real mother hen Chef d'oeuvre of biological diversity, Membracidae astonish us and let us perplex because their forms are strange and eccentric. The curious and impressive expansions in front of their head or in extension of their prothorax make real alive sculptures of them. Tricks of nature or mimicry, these insects somewhat "baroques" surprise by the extravagance and the great diversity of their outgrowths. What were the environmental constraints and pressures which in that way shaped these odd expansions? The long path of living molded these protuberances in curious cuticular prolongations in front of the head or starting from the first thoracic segment (prothorax): spherical sizes, curved or right spines, arabesques, horns, roundnesses and more or less complex structures form the Membracidae exoskeleton. Their aspects are varied as much: hairy to smooth, rough and polygonal even reticulated or similar to bark, dented, translucent or opaque, colored or cryptic. These empty hulls, of impressive sizes make the flight difficult for some species, but Membracidae remain very sharp in their jump. The males can be very different from the females regarding the morphology. After mating, from which the positions are very different according to the structure and the form of the outgrowths, the female, at the time of the laying, inserts directly in the living tissue of their host plant, either a single egg or plenty of them, or glue it on the surface. Some species coat them with a frothy substance which, while drying, becomes hard. The very protective females (they cover the eggs with their body), will form groups by indifferently mothering the larvae and the nymphs of the ones and others until the adulthood, which would lead us to believe that they have a "maternal instinct". Discreet, females are tented by ants Because of their small size (approximately 1 cm length), Membracidae are often unseen or very difficult to spot. Among the 2500 species which belong to the Homoptera order, many, solitary and discreet, remain badly known. Only those are studied which are gregarious and have mutualistic relations with ants. Homoptera live on annual or perennial plants and sucks the sap from which they feed nutritive compounds thanks to a complex digestive system. The excrements are rejected in form of small sweetened droplets, the honeydew. This very sticking liquid is difficult to eliminate mechanically regarding the sedentary and the quasi-immobility of those species. It isn't seldom to find an insect definitively fixed on the host plant, killed contaminated and invaded by moulds. Their sweetened excrements are an appreciable source of food for the arboreal and opportunistic ants which intense foraging activity facilitates the meetings with the sedentary females which then develop gregarious habits. Mutualistic associations are very complex and multifactorial. Mutualism are found between the two species only if the benefit is important for each one: for example, protection (against the predatories) and care (to inhibit parasitism, to avoid diseases from fungus) in exchange of a great production of honeydew. This production is carried out when the ants claim for and incite the evacuation of the sweetened liquid in "stroking" the insect with its antennas. The weak operating cost for the ants, an easy access and a short-haul until the place of harvest increase association between the two species. The host plant takes profit from the protection thus brought to the Membracidae by the ants because they will push away all the specialized plant-eating animals. The predatory are wary about The tropical forest is rich, plentiful of life. From the litter untill the top of the trees, life is omnipresent. The extraordinary variety of the species is without end, the multitude of the forms incredible. The small insects of the Membracidae family are one of the most significant representatives. Neither aggressive, nor equipped with natural defensive means (darts, mandibles) so they probably developed imitations in compensation that could be at the origin of their outgrowths. As these which looks like the buds of the host plant amazingly, or those which, scattered on the stem with their outgrowths pointed towards outside make think of spines of certain shrubs, or others which prolongations remind fine desiccated branchlets. First of all one could think that this tiny world, if peaceful and quiet. It is only one impression, because some species share a very advanced technique. Several types of acoustic signal, inaudible sounds to human, are transmitted thanks to the vibrations made by tapping the legs on the stem of the host plant for example. When a young feels threatened, the vibrations so created are communicated within the group of the larvae and the nymphs. Together, they tap the stem to alert the mothers who come to defend them by using the power of their posterior legs or by beating their wings vigorously. Thus they can push back predatory much more bigger in size. Other sound vibrations are used by the males which drum the plant with their abdomen to attract females. Predatories, like various Arthropods, Arachnida and Hyménoptera (wasps) can be pushed back by the mothers at first sight so placid but foolhardy when their offspring should be protected. Birds or other predatories which which feed on Membracidae are terribly wary. The hooked spines, horns and other points with which some species are provided in number wound the throat or are planted in the tissue which could then be infected and then later kill the animal. To counter the attacks of the animals, some species of Membracidae have precuts at the base of their outgrowths which break or are detached when they are snapped up, allowing the insect to escape. These attractive insects, mini-monsters or wonders of nature still keep very mysterious. If one can easily observe most common of them which live in partnerships with the ants, how much are those, solitary in the heights of the trees, that remain to us unknown? Membracidae, dazzling for the ones, pushing back for the others, but don't let indifferent at all, are the witnesses of the immense diversity of the species.

Captions 1 Cladonota latifrons. An imitation which curiously points out a desiccated branchlet 2 Cladonota benitezi, female. Strong dimorphism with the male (3). 3 Cladonota benitezi, male. 4 Smerdalea mminens, fullface. 5 Smerdalea imminens, female. 6 Bocydium globulare, fullface. 7 Bocydium globulare, in profile. 8 Cladonota sp. male. 9 Heteronotus nigrogiganteus, The hooked spines, horns and other points with which some species are provided in number wound the throat or are planted in the tissue which could then be infected and kill later the animal consequently. 11 Heteronotus nigrogiganteus, from the top. 12 Heteronotus delineatus. 13Heteronotus delineatus, fullface. 14 Heteronotus maculatus, see 9. 15 Heteronotus albopunctatus, see 9. 16 Umbelligerus peruviensis, see 9. 17 Head of Umbelligerus peruviensis. 18 Heteronotus delineatus. 19 Heteronotus delineatus, fullface. 20 Atypa bucktoni. 21 Anchistrotus maculatus, has precuts at the base of its outgrowth which break or is detached when it is snapped up, allowing the insect to escape. 22 Anchistrotus maculatus, fullface. 23 Lycoderes gladiator, fullface. 24 Oeda inflata. 25 Cyphonia clavata. While mating. 26 Stegaspis fronditia, female. 27 Head of Stegaspis fronditia, female. 28 Stegaspis fronditia, female from 3/4. 29 Stegaspis fronditia, female on a flower. 30 Stegaspis fronditia, female with an ant Dolichoderus bispinosus, see 41. 31 Stegaspis fronditia female. The excrements are rejected in form of small sweetened droplets, the honeydew. This very sticking liquid is difficult to eliminate mechanically regarding the sedentary and the quasi-immobility of those species. It isn't seldom to find an insect definitively fixed on the host plant, killed contaminated and invaded by moulds. 32 Stictopelta squarus. looks like the buds of the host plant amazingly. 33 Head of Stictopelta squarus. 34 Membracis flaveola. 35 Head of Membracis flaveola. 36 Enchophyllum cruentatum. 37 Enchophyllum cruentatum, de face. 38 Lycoderes fernandezi, female of its laying. Gregarious they are scattered on the stem with their outgrowths pointed towards outside make think of spines of certain shrubs. 39 Idem Lycoderes fernandezi, female of its laying. 40 Tritropidia bifenestrata. with a larvae. 41 Larvae of Tritropidia bifenestrata, babied by an ant Dolichoderus bispinosus. Mutualistic associations are very complex and multifactorial. Mutualism are found between the two species only if the benefit is important for each one: for example, protection (against the predatories) and care (to inhibit parasitism, to avoid diseases from fungus) in exchange of a great production of honeydew. This production is carried out when the ants claim for and incite the evacuation of the sweetened liquid in "stroking" the insect with its antennas. The weak operating cost for the ants, an easy access and a short-haul until the place of harvest increase association between the two species. The host plant takes profit from the protection thus brought to the Membracidae by the ants because they will push away all the specialized plant-eating animals. 42 Larvae an mature Tritropidia bifenestrata on its laying, see 41. 43 Female of tritropidia bifenestrata with egges, larvae and ants Dolichoderus bispinosus, see 41. 44 Tritropidia bifenestrata. When a young feels threatened, the vibrations so created are communicated within the group of the larvae and the nymphs. Together, they tap the stem to alert the mothers who come to defend them by using the power of their posterior legs or by beating their wings vigorously. 45 Oriola picta, female on its laying. 46 Oriola picta, female on its laying, seer 41. 47 Gerridius fowleri, female on its laying. 48 Gerridius fowleri, female on its laying with ant Dolichoderus bispinosus. 49 Lycoderes fabricii. 50 Enchenopa albidorsa, with a louse (in red). 51 Enchenopa albidorsa, see 38. 52 Enchenopa gracillis, see 38. 53 Nassunia binotata. 54 Bolbonota insignis, This one looks like an bird excrement. A perfect imitation ! 55 Stegaspis fronditia, male. 56 Tynelia pubescens. 57 Certainly a larvae of Anchistrotus. For more informations : Hôlldobler, B. & E.O. Wilson. 1990. The ants. The Belknap Press of Harvard University Press, Cambridge, Massachusetts. (Gullan, P.J. and Kosztarab, M. -1997- Adaptations in scale insects. Annual Review of Entomology 42: 23-50). Rex Cocroft, The inside story of insect song, American Museum of Natural History, October 1999

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