164 THE entomologist's record. 



become one by one, either radius or cubitus nervules. This altera- 

 tion of position often causes one nervule to fork on to another, especi- 

 ally at the angles of the cell. In Hcpialus huinuli (PI. I., Fig. 1) the 

 hind-wings are asymmetrical in the position of the nervules, and 

 illustrate how such forking occurs ; some of the higher groups {('.(/., 

 Nymphalids, etc.), after the loss of the median nervules, as such, 

 also lose the transverse nervules which form the cell ; sometimes a 

 nervule coalesces with another, and they merge into one ; sometimes 

 a nervule becomes weak and is lost in the higher groups ; the loss of 

 any other nervure, besides the median, indicates a high modification. 

 We may assume that modification of neuration in the Lepidoptera 

 tends to a reduction in the number of nervures, and once lost, or the 

 position altered, neither is ever regained. That an increase in the 

 number of nervules does occur, Plate I., fig. 3, Zeuzcra pyrina, proves. 

 In this fig. the left fore-wing has the normal number of nervules, 

 the right, however, has an increase of one ; this may be an accident, 

 or an attempt to throw back to an ancient number. On plate D, 

 fig. 4^, Knt. Fu'c, vol. iv., is shown on abnormal increase in the 

 number of nervules. The explanation of this seems to be that as 

 nervules 3, 4 and 6 failed to reach the margin, the neuration, in 

 order to support the membrane, developed branches from nervule 5, 

 otherwise it is probable the wing outline would have been indented. 

 Though I do not think an aberrational increase in number of nervures 

 is ever transmitted to descendants, I intend to work up the subject. 



From the foregoing it will be seen that the total number and 

 position of the nervures is an important consideration, and I venture 

 to give a system of numbering, by means of which our workers at 

 special groups (Prout, Bacot, and others) could give a written descrip- 

 tion of the neuration of those groups, and show how far neuration 

 agrees with the conclusion arrived at by other lines of study. The 

 nervules should always be named and numbered from the nervure to 

 which they are distinctly attached. Thus, a description of the neura- 

 tion of Cumdae, fig. 5, would read as follows : — 



+ Costal or Subcostal or Discoidal Mediau or Submedian 

 ft Subcostal. Radius. or Media. Cubitus. or Anal. 



1 1.3.3.4.5* 1.2.3. 2.1 2.1 = 13 fore. \ 



1 1 1.2.3. 2.1 3.2.1 = 10 hind. ) 



This may be compared with the neuration of Sinerinthidi, fig. 8, 

 thus : — 



t Costal or Subcostal or Discoidal Median or Submedian 

 ti Subcostal. Radius. or Media. Cubitus, or Anal. 



1 1T3.4.5* 1^ 3.2.1 1 = 11 fore. \ 



1 1.2*'' 1 3.2.1 2.1 = 9 hind. [ 



It will be observed that there is no median nervure in the fore and 

 hind-wing, whilst S 1 and R 1 are connected in hind-wing, and it can be 

 seen at a glance that Swi'rhit/tidi is the higher group. The fore-wing 

 has one median nervule only, which remains at the end of the cell ; 

 two nervules then have been lost, as also the median nervure. The 

 hind-wing has one median nervule only remaining, the radius has 

 acquired one, and cubitus another, and one anal nervule is lost. It is, 

 of course, only specialists in neuration who could say that radius 5 is 



* V Indicates a forking of two nervules. t Kirby. tt Comstock. 



