ARMATURE IN THE EUROPEAN RHOPALOCERA. 359 



1. Stimcture of the Apical Segment. 



In discussing this and other points of the genital armature, it will be convenient to 

 take one species as the type or standard with which to compare all others ; and in 

 selecting PJpinephele Hyperantus, L., as the type or standard species, I wish to remark 

 that I do not claim for it any special position amongst the butterflies. 



The typical structure, then, is that in which (looking at it from the side) the hind 

 margin of the segment is perpendicular, or nearly so, for about half the distance (less or 

 more) from the upper margin to the lower margin, and then slopes obliquely forward 

 (ie. towards the head of the insect) -till, at the lower margin, it nearly meets the hind 

 margin of the penultimate segment (PL LY. figs. 1 & 2). This form I shall term the 

 typical or angular. The oblique portion may be either straight, or slightly concave, or 

 convex. The iipper margin, or dorsal surface, is slightly sloped backwards, so that the 

 height of the orifice is rather less than that of the penultimate segment. The lateral 

 surfaces are gently rounded towards the longitudinal furrow (pleurite) which marks on 

 each segment the division between the dorsal and ventral arcs. Eor this reason the orifice 

 viewed from behind presents a long oval outline, slightly constricted at about one third 

 the distance from the lower margin. Viewed from above, the hind margin of the segment 

 presents a flatly rounded outline (PI. LV. fig. 3). 



2. Modifications of the Apical Segment in the various Families. 



I must first premise that for this and other parts of the structure the appearance is 

 described as seen in profile from the side, unless when stated otherwise. 

 ' Papilioned^. Structure various. In Papilio Machaon (PI. LVI. fig. 40 a) only the 

 upper half is visible, and is triangular in form, assuming the character of the tegumen, 

 for which I mistook it. In P. Alexanor there is a similar modification. In P. Poda- 

 lirim (PL LVI. fig. 39 a) the hind margin is perpendicular. In Thais Polyxena 

 (PL LVII. figs. 1, a, b) and T. Medisicaste (PL LVII. figs. 2, a, b) the hind margin is 

 concave, and the segment assumes to a certain degree the character of the tegumen. In 

 Parnassius Apollo (PL LVII. figs. 3, A, B, c) and P. Delius there is a considerable departure 

 from the type, the segment being long oval in outline, excavated for half the distance above, 

 and nearly closed below. In P. Mnemosyne the departure from the type is not so great. 



PiEEiDiE. Hind margin more frequently oblique throughout than angular (PL LVI. 

 figs. 27 a, 28 A, 29 A, 30 a, 31 a, b, 33 a, 37 a, b, and 38 a, b). In Colias there is an oblong 

 prolongation in the direction of the dorsal mesial line (PL LVI. fig. 36 A from side, b 

 from above). In Leucophasia the structure is very aberrant. Prom the side the 

 outline is oblong, roimded at the apex ; from above oblong, rounded, and deeply emar- 

 ginate at apex ; from below it appears widely split to the base, with a triangular piece 

 partly filling the aperture (PL LVI. figs. 34 a side, b above, c below). 



Ltc^nidje. Angular (PL LVII. figs. 4 A, 12 A, 13 a), or perpendicular (PL LVII. 

 figs. 17 a, 18 A, 19 a), more rarely concave (PL LVII. fig. 14 a). 



Erycinid^]. Angular, approaching oblique (PL LVI. fig. 26 a). 



Libytheid^!. In the single European species, Libythea celtis, the structure is aberrant. 



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