FOSSIL TXSKCTS OF TIIK BRITISH COAL MEASURES. 



may have dwelt in (.lamp earth rather than in water, ami that ''the formation of 

 the larval traeheal system undoubtedly proves that this at one time was the case. 

 It mav well have been so in Carboniferous tunes." 



Tillyard's views are well worth ((noting in full, espeeially as they support in 

 some measure those of t'ruvost : " \Ve mav pietnre to ourselves the giant insects 

 of Cominentry as inhabiting the shores of a large, shallow, nearly stagnant 

 lake. In the muddy oo/e around its borders grew forests of the Giant Mare's 

 Tail, while further buck on the sandv slopes the graceful C'ycads and other extra- 

 ordinary plants formed a more diversified medlev. There, amidst rotting vegetation, 

 these insects lived and bred. In such almost amphibious conditions it may well be 

 that the larva 1 of Protepliemeroidea and Protodonata first began that series of 

 adaptive changes which finally led them to adopt a purely aquatic mode of life." 



The lar\;e of Ilr/iilin and of other forms whose wings I describe under the 

 name of "Pteronepionites" must have lived under conditions fitted for their gradual 

 metamorphosis. The body was long, well segmented, and bore rudimentary 

 wings, which were carried well up over the thorax in an erect or semi-erect posit ion. 

 Though rudimentary, the wings possess features which may have determined to a 

 large extent the mode of life. They are attached by broad, strong bases to the 

 thorax, and are very muscular, as shown by the stout ridges proceeding from the 

 point of attachment into the wings, and the anterior margins are also thickened. 

 The bodies with their lateral expansions of the terga are very suggestive of those 

 of the Diplopoda, and like them would offer no serious obstacle to progression 

 through rank and rotting vegetation. That these larval insects would also 

 penetrate soft muds, if necessary, in search of food is possible, since the 

 soft-bodied caterpillars of the Hawk-moths of to-dav are able to enter hard soil 

 before pupal ion takes place. 



The stout wing-bases and the strengthened margins of the WHILES would 

 prevent damage to these structures as the larva? crawled about, or sought to bury 

 themselves in the soil or muds. They were essentially adapted for a ground 

 habit. Whether they were capable of an aquatic or semi-aquat ic habit can only 

 be settled by a knowledge of the mode of respiration. 



Lubbock, Gegenbaur and others have adduced strong reasons in favour of an 

 aquatic origin of the insects, ami in the Carboniferous types we should naturally 

 expect that t he original habits had not had time to undergo any great modification. 

 Larval wings ol the " Pteronepionites' Ivpe must have been living structures in 

 \\hich metabolism was active, and very unlike tin: dried membranous sac-like 

 expansions of the adult insect. The growth of the larval wind's was continued 

 throughout metamorphosis, ami during this period then- delicate nature, broad 

 expanse, and the thinness ol the inlegiiiiienl may have enabled them to assist in 

 the respiratory fund ion. 



The researches of Comstock and Xeedham show thai larval \\ IIILI'S of recent 



