Page:Popular Science Monthly Volume 68.djvu/249

Rh recent cockroaches. The thick arched front wing with strongly delimited anal area dates from the Carboniferous. The group, however, has by no means remained stationary since the Carboniferous. On the contrary, close observation reveals evidence of advance along distinct and definite lines. The Carboniferous cockroaches are provided with a long ovipositor resembling that of the katydids or crickets; modern cockroaches have a reduced and specialized ovipositor. Early cockroaches no doubt deposited their eggs in the ground or under the bark of trees or within the tissue of succulent stems; modern forms deposit their eggs in a very characteristic egg case. The front wings

have become in general more resistant, the venation more complicated. The hind wings have developed plications and a longitudinal fold. The value to biology of a study of the group is in direct proportion to the completeness with which these changes and the laws governing them can be traced out.

The wing of a typical cockroach of Carboniferous time is of simple structure. A border vein, the costa, traverses and strengthens the costal border. Four strong veins arising close together near the base of the wing diverge and supply the greater part of the wing membrane. The first of these, the subcosta, meets the costal border about or beyond the middle length of the wing; numerous superior branches are