THE INSECTS OF THE COAL 37 



nervous system, so that the thoracic ganglia were 

 separate instead of concentrated. The most interesting 

 distinction, however, was the possession by many species 

 of a pair of prothoracic appendages much resembling 

 miniature wings, and which especially suggest the appear- 

 ance assumed by the anterior pair (tegmina) in existing 

 Phasmidae. There is some evidence in favour of the view 

 that they were articulated, and they exhibit what appears 

 to be a trace of venation. Brongniart concludes that 

 in still earlier strata, insects with six wings will be 

 discovered, or rather insects with six of the tracheal 

 gills sufficiently developed to serve as parachutes. Of 

 these, the two posterior pair developed into the wings 

 as we know them, while the anterior pair degenerated, 

 some of the Carboniferous insects presenting us with 

 a stage in which degeneration had taken place but was 

 not complete. 



One very important character was, as I have already 

 pointed out, the enormous size reached by insects in 

 this distant period. This was true of the whole known 

 fauna as compared with existing species, but it was 

 especially the case with the Protodonata, some of these 

 giant dragon-flies measuring over two feet in the expanse 

 of the wings. 



As regards the habits of life and metamorphoses, 

 Brongniart concludes that some species of Protoephe- 

 meridae, Protoperlidae, &c., obtained their food in an 

 aquatic larval stage, and did not require it when mature. 

 He concludes that the Protodonata fed on other animals, 

 like our dragon-flies ; that the Palaeacridiidae were 

 herbivorous like our locusts and grasshoppers, the 

 Protolocustidae herbivorous and animal feeders like our 

 green grasshoppers, the Palaeoblattidae omnivorous 

 like our cockroaches. The Homoptera, too, had elon- 

 gated sucking mouth-parts like the existing species. It 

 is known that in Carboniferous times there was a lake 

 with rivers entering it, at Commentry. From their great 

 resemblance to living forms of known habits, it is 

 probable that the majority of these insects lived near 

 the water and their larvae in it. 



