694- 



THE PANORPOID COMPLEX, 111., 



2A 1A Cu, Cu lb Cu u M J+4 



Text-Fig. 104. 



Wings of Sialis lutaria Linn., (fam. Sialidae), (x6). Lettering as 

 on p. 535. 



genus tends to become unique in having the terminal branches 

 of R2+3 arranged anteriorly, instead of posteriorly. 



It should be noted here that there is really no justification for 

 the assumption that there has been any constant addition to the 

 branches of the main veins in the Sialidae, by terminal twigging 

 or splitting, such as is found in the Planipennia. No such ad- 

 ditions are to be found either upon M or Cu; and il is purely 

 a gratuitous assumption to say that they are present on Rs, when 

 the condition of that vein is much more reasonably derived 

 directly from the older Corydalid type. 



We may, then, fairly assume that the Sialidae are a reduced 

 offshoot from the older Curydalidae. Such a conclusion is sup- 

 ported by the whole weight of the evidence from other charac- 

 ters, the Corydalidae being, both in their morphology and life- 

 histories, by far the more archaic of the two families. 



A typical archaic Corydalid genus is the Australian Archi- 

 cl/auliodes (Text-fig. 105). in tins genus, Cu retains the ori- 

 ginal three-branched condition, without any alteration in the 

 position of its forkings; M is generally reduced either to three 



