Archived content - Cicada (8 of 46)
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B. Understanding Cicadas
5. Origin and Evolution
Cicadas seem so very different from all other insects that one might think, like the ancients, that they arose spontaneously from the earth. But studies of fossils that represent their extinct relatives (Sections 5A, 5B), and specimens of their modern cicada relatives (Section, 5C) fully bear out what scientists have long known about evolution: that living things slowly change over great expanses of time to suit their changing environments, and with them, their very bodies adapt to new shapes and functions. Why this happens is explained by natural selection operating on heritable characters (genetic material). Whatever the source of such changes, the results are marvellous indeed, far exceeding the wildest imagination of humans.
It is often difficult to tell what the ancestors of modern insects were like. Fossils of insects are usually so badly crushed that only the wings remain. Even the better-preserved specimens that retain body parts are often disarticulated and distorted so that their natural form is hard to discern. For example, one such cicada-like insect was described recently as a horse fly Footnote 1. Nevertheless, there have been some notable exceptions to this rule, which permit us a rare glimpse of the remote past.
Not all insects that look like cicadas are related to them. The so-called Protohemiptera from the Carboniferous era (more than 300 million years ago) have long "beaks", but details of the mouthparts show that they are forceps-like jaws, probably used for removing seeds from cones. Their relationship is actually to ancient dragonflies.
The fossil record of cicada-like insects (Cicadoidea) extends further back in time than that of most other cicada relatives. Two families of cicada-like insects are known from 100-200 million years ago (throughout the Mesozoic era, the age of dinosaurs). The generalized bugs from which they probably arose, the Prosbolidae, are older still, having been widespread in the Permian (the upper level of the Palaeozoic era). The family Cicadidae first appear as a fossil nymph Footnote 2 of Cretaceous age with fully developed digging legs, implying that cicadas went underground when birds were evolving. However, a dubiously identified “cicada” nymph may be more than 130 million years old (Jurassic). Modern genera of Cicadidae (Lyristes, Meimuna, Tibicina) have been found that are more than five million years old (Miocene). These co-exist along with extinct genera (Lithocicada, Tymocicada), showing that the family was diversifying rapidly at that time.
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