174 THK WING-VENATION OF LEPIDOPTEKA. 



tween M3 and M4); Afo^ between Cuia and Cuii, — ft. = ptero- 

 stigma. 



Postscript (added April 16th, 1917). — Since the above was 

 written, I have carried out an exhaustive study of the Austra- 

 lian Mecoptera (Scorpion-flies) in my collection. These consist 

 of representatives of the families Bittacidca, Choristidce, and a 

 remarkable new family of very small Scorpion-flies, which will 

 be dealt with in a separate paper. As 'these last are strong- 

 flying insects, in which the wings appear to be connected during 

 flight, I examined their wings for signs of a coupling-apparatus. 

 I found that they all possessed a well-formed basal coupling- 

 apparatus of the type described for the Neuroptera Planipennia, 

 viz., a juyal lobe near the base of the forewing posteriorly, and 

 a juyal process anteriorly on the base of the costa of the hind- 

 wing. From this jugal process there arise two strong bristles 

 directed obliquely outwards, so as to constitute a true frenulum, 

 exactly homologous with that found in Planipennia, and in the 

 females of many moths. The same structures are present in 

 Choristidce, but smaller, while their vestiges can be seen even in 

 the Bittacidce. 



Since, therefore, the frenulum has been shown now to occur 

 normally in three Orders, while the juyum (as developed iu the 

 Hepialidce) is not to be paralleled outside the Order Lepidoptera, 

 it is clear that we must revise our ideas of the relative archaism 

 of the Jugatai and Frenatse. The original or ancestral Lepi- 

 dopteron must have possessed a frenulum derived from an 

 ancestor common to the Lepidoptera, Mecoptera, and Plani- 

 pennia. On the other hand, the jugum of Hepialidct must have 

 been a very early specialisation developed from the ancestral 

 jugal lobe of the forewing, with complete loss of the original 

 frenulum on the hindwing. The Micropterygidtt must have 

 followed a somewhat similar (possibly even earlier) line of 

 specialisation. 



The Frenatai or Heteroneura, then, are the main stem of the 

 Lepidoptera, while the Jugatte or Homoneura are an archaic 

 side-branch, from which no other existing families of the Order 

 can possibly have been derived. it.J.T. 



