136 HELICONID.E. 



NOTE. 



Before dismissing this family, it will not be useless to direct our attention for a moment to the sexual variations in 

 the Neuration of the Posterior Wings in some of the genera, especially as they afford much light on the homologies of 

 the nervures and nervules. As far as my observations extend, these variations occur in no other family of the Diurnal 

 Lepidoptera, and in this family are confined to that group in which there exists the greatest sexual difference in the 

 developement of the anterior legs. 



In the normal, or at least most common, structure in the Diurnal Lepidoptera, we find the discoidal nervure 

 becoming, as it were, a third subcostal nervule ; and as such it has always been regarded by the few authors who have 

 paid attention to the structure of the wings in this order. This is the prevalent character in the first genera of 

 Ileliconidre, though, as we approach those genera in which the anterior legs of the male are least developed, we find a 

 slight change, thus approaching some of the Ithomia?. 



In these the cell is closed by two distinct disco-cellulars, both crossing the wing nearly at right angles to a 

 line drawn from the base to the apex ; the subcostal nervure evidently only two-branched, the discoidal nervure 

 often extending considerably into the cell, where it becomes gradually atrophied. But in the males of many 

 Ithomiaj we find the upper disco-cellular nervule directed very obliquely inwards and downwards; the second 

 subcostal nervule, at its origin, directed downwards, then bent outwards at a right angle. The cell is much 

 longer than in the females, owing to the obliquity of the upper disco-cellular, which unites with the second subcostal 

 nervule at the point where it is bent at a right angle. 



Numerous smaller variations occur in the different species of this genus, as will be seen by a reference to the 

 sectional characters given, which, however, must not be taken too strictly, but as indicating the general type of 

 structure in the section, for almost every species exhibits some small variation. 



We will now pass to the next genus, Mcchanitis, in which the lower disco-cellular nervule appears to be a continuation 

 of the median nervule, the exact course of which it follows, and thus the discoidal nervure appears a fourth median 

 nervure. The discoidal nervure is remarkably bent above the point where it anastomoses with the lower disco-cellular, 

 and again at its union with the upper disco-cellular. This structure is found in both sexes, and also in the females of 

 the next genus, Sais. But here the males offer a new character, of which the extreme type is shown in Sais 

 Cyrianassa. In these, the upper disco-cellular nervule, as well as the lower, is apparently a continuation of the median 

 nervule, and thus there appear to be five median nervules, the second subcostal being bent at its origin, so as to give 

 to its basal portion the appearance of a short disco-cellular, and thus the subcostal nervure appears to be simple. 



We, therefore, can trace the discoidal nervure and disco-cellular nervules, first occupying in the females their normal 

 position, normal as regards the whole order, whilst in the males of the same species there is a change in the position of 

 the upper disco-cellular ; thence in both males and females of one genus, and in the females of the next, presenting us 

 with changes in the position of the lower disco-cellular and the discoidal : lastly, still further changed in the males only. 



This gradual change in the position of the discoidal nervule is very interesting, from its explaining fully the 

 supposed anomaly of the anterior wings of the Papilionida?, which have been considered by all writers but myself to 

 have a four-branched median nervure. The anterior wings of Papilio, the posterior wings of Mechanitis, of many 

 species of Leptalis, and of the females of Sais, exactly agree in this apparent anomaly ; and the anterior wings of some 

 species of Leptalis have much the same structure as those of Parnassius. The resemblance in the neuration of the 

 posterior wings in some species of Leptalis, with those of some of the Heliconida;, is remarkable from its occurring in 

 those species which approach most nearly to the Heliconidne in form and colour, and seems to prove considerable 

 affinity between the two groups. 



The generic character of I tuna requires a slight alteration ; the lower disco-cellular nervule of the posterior wing 

 being sometimes united to the third submedian nervule shortly beyond its origin. 



