GEOLOGICAL HISTORY OF COCKROACHES 



249 



Fig. 7. Young of a Coal Meas- 

 ure cockroach, X 4. Original 

 drawing. 



roaches in any rocks older than the Carboniferous. The single speci- 

 men reported from the Silurian of France is at best very unlike a 

 cockroach. Its claim to affinity with the cockroach group was long 

 ago contested by Scudder, and even Brong- 

 mart, its discoverer, has since conceded that 

 it can not belong here. Other writers ex- 

 clude the fossil entirely from the class In- 

 secta. The oldest known species appear to be 

 Archimylacris parallela Scudder and Gera- 

 blaitina fascigera Scudder, from the Mill- 

 stone Grit, or Middle Carboniferous. Dur- 

 ing Coal Measure time cockroaches became 

 extremely abundant, more so than in any 

 later period. They are less numerous in 

 Middle and Upper Permian as well as in 

 Mesozoic and later deposits. Nothing what- 

 ever is known of the insect life of the south- 

 ern hemisphere during either Paleozoic or 

 Mesozoic, and it yet remains to be seen what 

 forms will be brought to light from this part of the world. During the 

 Carboniferous and Permian, cockroaches were widely distributed over 



Europe and North America. With the 

 uniform climatic conditions of that 

 time it can hardly be doubted that their 

 distribution was as wide at least as that 

 of the tropical plants with which they 

 are so constantly associated. 



Among the laws of development 

 operative in bringing about the changes 

 which have occurred in the cockroach 

 family during its long geological his- 

 tory, those the effects of which are most 

 apparent may be summarized under the 

 following headings : 



Recapitulation of Ancestral Char- 

 acters. — During the nymph stages of a 

 modern cockroach the venation of the 

 immature wing is not unlike that of the 

 typical Coal Measure adult. The main 

 veins of the wing, which during these 

 early stages are free to the base, later become more or less fused and 

 cross veins appear, thus illustrating the law common to most groups of 

 organisms and known as a recapitulation of ancestral characters. 



Fig. S. Natural size restoration of a 

 typical Coal Measure cockroach, Eto- 

 blattina mizona. The protruding ovi- 

 positor and simple wing venation dis- 

 tinguish Coal Measure from modern 

 cockroaches. Author's illustration. 



