Endangered Species Handbook

Print PDF of Section or Chapter

Madagascar and other Islands

The Biological Wealth of an Impoverished Country: Invertebrates

Like the rest of its fauna, Madagascar's invertebrates are extraordinary. One insect from the age of the dinosaurs, the Giraffe-necked Weevil (Trachelophorus giraffa), has an elongated neck which rises vertically, then makes a right-angle turn and extends horizontally, and ends in a tiny head with furry antennae. Amazingly, this insect has counterparts in New Zealand known as giraffe weevils (Molloy 1994). This may be explained by the fact that New Zealand was also part of Gondwana prior to its breakup (Molloy 1994). Other ancient species include the 100 species of hissing cockroaches. Some are far larger than any other cockroach species in the world; their heavy bodies resemble long-extinct trilobites. The largest species measure up to four inches long, and thousands are exported for the novelty pet trade and for zoos. When touched, they hiss loudly, and males aggressively charge one another with their armored, knobbed shields (Preston-Mafham 1991).
One of the richest land-snail faunas in the world is native, with more than 380 species named so far, 361 of which are endemic and differ greatly from land snails in Africa (Preston-Mafham 1991). Many are threatened, however, by introduced African Giant Snails (Achatina fulica) and several other non-native snails introduced to control the African Giant Snail, but threatening native species instead. One native snail, Tropidophora deburghiae, is considered endangered by some authorities. Brilliantly colored slugs, or shell-less snails up to 6 inches long, striped in black-and-red or yellow-and-brown, live on the damp rainforest floor (Preston-Mafham 1991). Many have limited distributions and can be easily eliminated by habitat destruction (Preston-Mafham 1991).
An extremely ancient family of spiders, Archaeidae, first described from a specimen frozen in amber several million years old, has seven species on Madagascar, one in South Africa, three in Australia, five in New Zealand and one at the tip of South America; these species appear to be vestiges from the ancient supercontinent (Preston-Mafham 1991). The Archaeidae spiders have strange, grotesquely shaped bodies, visible only through a microscope since they are only 0.14 inches long; they live among leaf litter on the ground (Preston-Mafham 1991). Some Madagascar spiders are extremely bizarre, with shapes that resemble bat-winged leaves, bright red thorns, or mottled brown lumps on logs (Preston-Mafham 1991).
Millipedes on Madagascar reach 6 inches and exude droplets of poison when attacked; Brown Lemurs have found ways of avoiding this toxin and feed on them (Preston-Mafham 1991). Shield-bugs, or stink-bugs, of the family Pentatomidae, have 220 species on Madagascar, many of which are brightly colored in reds, oranges and blacks; 120 species of water bugs, of which 80 percent are endemic, and a variety of assassin bugs add to the rich insect fauna (Preston-Mafham 1991). About 20,000 beetle species, including 500 species of endemic jewel-beetles, are native to Madagascar. Jewel-beetles, with their colorful, metallic bodies, appear during the rainy season in southern and western forests (Preston-Mafham 1991). Many species of scarab beetles, among which are dung beetles, are also native to Madagascar; one endemic genus, Helictopleurus, roll the dung balls into their nests and lay their eggs in them (Preston-Mafham 1991).
Madagascar's butterflies, totaling 300 species, are not as diverse as in some parts of the world, such as the Tambopata Natural Reserve in Peru, which has 1,300 species. This may be because they colonized the island fairly recently. Another possibility is that many species have faded into extinction, leaving no trace, when the plant species upon which they depended were driven to extinction by habitat destruction. Since 80 percent of the island's forests have been cut, hundreds or thousands of species may have disappeared without a trace millennia ago. One Madagascar butterfly, a pale cream-and-black Swallowtail, Papilio mangoura, is hotly pursued by collectors because of its rarity (Preston-Mafham 1991). Several butterflies of the Nymphalidae family, or Fritillaries, are threatened, as are two species of the family Acraeidae.
In the 19th century, Charles Darwin learned of a spectacular, white Madagascar orchid (Angraecum sesquipedale) that had an extremely long, nectar-bearing tube dangling down from the flower. He reasoned that it could be pollinated only by an insect that could reach its nectar. He guessed that it might be "some huge moth, with a wonderfully long proboscis." Entomologists verified his belief with the 1903 discovery of the hawkmoth, Xanthopan morgani praedicta. This moth has a 9-inch tongue that it keeps wound in a spiral in its mouth, unfurling it to reach the nectar of this particular orchid. In a similar arrangement, another orchid (Angraecum arachnites), exudes a strange odor that attracts only one pollinator, the rainforest hawkmoth, Panogena lingens (Preston-Mafham 1991). The nectar at the base of this orchid's long, twisted tube can be reached only by this single species of moth--and not even every individual, but only one race of this moth which has a long, tapered proboscis (Preston-Mafham 1991). These species co-evolved, and should the moths become extinct, the orchids would have no pollinators and would follow them into extinction. Another unusual moth, the huge Comet Moth (Argema mittrei), is one of the largest moths in the world (Preston-Mafham 1991).


Back
Chapters
Chapter Index
Search
Animal Welfare Institute
Next
    ©1983 Animal Welfare Institute