208 Ancient Insects and Scorpions. 



The insects had previously been traced back to the Devonian 

 or Erian period, and the scorpions would now have antedated 

 them, but for another discovery made in Spain by M. Donville, 

 and communicated to the Academy of Sciences by M. Charles 

 Brongniart in December, 1 884. This is a wing of an insect in the 

 sandstone of the Middle Silurian, probably equivalent to our 

 Niagara series in Canada. This wing is shown by its venation 

 to belong to the Blattidse or cockroaches, a group already well- 

 known in the Carboniferous, where they seem to have thriven on 

 the abundant vegetable matter of that period. It differs, however, 

 in some of the details of venation from any living or fossil species 

 previously known. Brongniart proposes for it the name 

 Protohlattina donvillei, and as the beds containing this insect 

 are probably a little older than any of those containing the scor- 

 pions above referred to, this discovery makes the cockroaches, 

 still so numerous and voracious a family of insects, the oldest 

 known air-breathing animals. It is to be observed, also, that the 

 group which thus has priority belongs to the insects which have an 

 imperfect metamorphosis, and to the order Orthoptera. In connec- 

 tion with this, it seems that all the insects hitherto known in the 

 Carboniferous period belong (with the exception of species uncer- 

 tainly referred to the moths and the beetles) to the three closely 

 allied groups of Orthoptera, Neuropttra, and Hemiptera, all having 

 incomplete metamorphosis, so that in any case this group was the 

 dominant one of insects in the "Palaeozoic period. With the ex- 

 ception of a few lycopodiaceous plants we know nothing as yet of 

 Silurian land vegetation, but the Spanish Protohlattina suggests 

 to us the existence of Silurian forests producing some kind of 

 succulent and nutritious vegetable food, while it also furnishes an 

 explanation of the possible means of sustenance of the carnivorous 



scorpions. 



J. W. D. 



