700 THE PANORPOID COMPLEX, iii., 



loptera, is a rich one. It begins in the Upper Triassie of Ips- 

 wich, Queensland, and continues through the Lias and Upper 

 Jurassic of Europe. The dominant type of Planipennian wing 

 present in all these strata is that belonging to the family Pro- 

 hemerobiidae (Text-fig. 109). This may be defined as a very 

 primitive type, having no distal fusion of Sc with R 1 no spe- 

 cialisation of the main stems of Sc, Rj and Rs to form a vena 

 triplica like that of the Psycho pshlae, and no definitely arranged 

 system of cross-veins. Superimposed upon this very archaic 

 foundation is a highly specialised condition of the radial sector, 

 in which the pectinate condition of the branches is very clearly 

 marked . 



The oldest known fossil Planipennia, viz. Archepsychops (28) 

 and Protopsychopsis (5) of the Ipswich Trias, are definitely 

 Prohemerobiid types, as I have already proved. The former, 

 moreover, shows such close affinity with the still existing Mega- 

 psychops of the family Psychopsidae, that there can be no doubt 

 of the origin of this latter family as a direct offshoot of the 

 ancient Prohemerobiid stem (28) . 



We have now to consider whether there may not still exist 

 some archaic type, which may be considered to be either truly 

 Prohemerobiid in itself, or even, perhaps, older than the fossil 

 types so far discovered. Such a type is surely to be found in 

 the Ithonidae (12, 30), an archaic side-branch of the Order, 

 confined to Australia, and differing from all the other Plani- 

 pennia in the possession of a melolonthoid larval type, in which 

 the paired sucking jaws are of a very primitive form. 



The type of venation in this family is definitely Proheme- 

 robiid, but even more archaic than are many of the fossils of 

 that family, in that the dichotomic forking of R- 4 5 * is still 

 preserved in the majority of specimens; and the resemblance to 

 the Megalopterous type of venation is even closer than is the 

 case with the fossils. 



The specialisations to be seen in the venation of Itlwne, apart 

 from the pectination of Rs already mentioned, are the abundant 

 additions to the branches of the main veins, in the form of ter- 

 minal twigs or branchlets, and the apparent complete loss of 

 M 5 . The former is an ordinal character for the Planipennia, 

 being clearly shown in all types except the excessively reduced 



*See foot-notes on pp.552, 692. 



