1898] 



THE NEURATION OF RHOPALOCERA 



393 



the next in sequence among the Pierids, viz. Euchloe, in which 

 incorporation of one of the median nervules with the radial system 

 of the fore wings forms (as in Hesperids) a six -branched radius. 



6-> 



Piei'is daplidice. 



Euchloe 



cardamiaes 

 (Pierids.) 



Leucophasia 

 sinapis. 



Further specialization among Pierids is by reduction in the number 

 of radial nervules in the forewings, and the movement of the remain- 

 ing median nervule towards the radial system. The transverse 

 ' cell ' nervure is a permanent feature throughout the Pierid group. 



Group 3. — Papilionids. The forewings have 

 five-branched radial system, four-branched cubitus, 

 only one median nervule remaining as such, a 

 transverse cubitus and connection near the base of 

 the wings, and two anal nervures. The hindwings 

 have a subcostal-radius connection, a very per- 

 sistent feature, which varies only so far as to 

 form larger or smaller ' cells ' in different genera. 

 One anal nervure only is typical of Papilionid 

 neuration. All other groups (i.e. Groups 1 and 

 2) have two anal nervures in the hindwings. 



From these notes it will be seen that however 

 widely the specialized Rhopalocera may differ, 

 the generalized forms of neuration have features 

 in common — five-branched radius, two median 

 nervules as such, three-branched cubitus in forewings (Groups 1 and 

 2). Ur Grote believes it is " uncertain " that the short anal nervure 

 of Papilionid forewings, is homologous with the rudimentary anal 

 nervure in the forewings of other groups, and conceives a separate 

 origin for Papilionids. In such groups of Heterocera as have two anal 

 nervures in the forewings, a rudimentary nervure is often present (see 

 Cossids), always at the base of that anal nervure farthest from the 

 cubital system. Comstock figures Megalopyge crispata, a ' low ' 

 moth which has an extension of the rudimentary nervure, a remnant 

 of a third anal nervure in the forewings. Most Rhopalocera have lost 

 one anal nervure (nearest the cubital system), a loss observed in many 

 Heterocera ; Papilionids retain two, one of which has become rudi- 

 mentary in other groups of Rhopalocera (also in Cossids and many 



2 E 



I'djiilin mackaon 

 (Papilionid). 



