ROACHES AND OTHER ANCIENT INSECTS
beds of the Carboniferous deposits, when insects were already fully winged. This fact shows how cautious we must be in making negative statements concerning the extinct inhabitants of the earth, for we know that insects must have lived long before we have evidence of their existence. The absence of insect fossils earlier than the Carboniferous is hard to explain, because for millions of years the remains of other animals and plants had
Fig. 57. Machilis, a modern representative of ancient insects before the development of wings. (Length of body 5⁄16 inch)
been preserved, and have since been round in comparative abundance. As a consequence, we have no concrete knowledge of insects before they became winged creatures evolved almost to their modern form.
At the present time there are wingless insects. Some of them show clearly that they are recent descendants from winged forms. Others suggest by their structure that their ancestors never had wings. Such as these, therefore, may have come down to us by a long line of descent from the primitive wingless ancestors of all the insects. The common "fish moth," known to entomologists as Lepisma, and its near relation, Machilis (Fig. 57), are familiar examples of the truly wingless insects of the present time, and if their remote ancestors were as fragile and as easily crushed as they, we may see a reason why they never left their impressions in the rocks.
Along with the Carboniferous roaches and the Paleodictyoptera, there lived a few other kinds of insects, many of which are representative of certain modern
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