16 Dr. T. A. Chapman on 



the male appendages. If there were no other reason to 

 separate palarica from stygne than the outline of the 

 clasps, I should certainly say they were not distinct. Still 

 there is a difference by which palarica differs from all 

 forms of stygne I have examined, and in which bcjarensis 

 is distinctly stygne and not palarica. The difference is 

 slight and difficult to seize, but in some specimens all 

 mounted in the same way, and at the same time,* of 

 palarica, and of Pajares stygne, the difference is constant. 

 In specimens otherwise mounted it would probably express 

 itself differently. In these preparations, the head of the 

 clasp in stygne expands gradually from the neck, and is 

 therefore long and not very broad ; the back of the clasp 

 is in one continuous curve, and there is a distinct notch or 

 step at the back of the head. In palarica the neck, is 

 narrower and continues narrow, and the back of the clasp 

 being, for some distance above the neck to the end, 

 straight and having no notch at the end, the head instead 

 of having nearly parallel sides, and so of quadrilateral form 

 as in stygne, has the front line at a considerable angle to 

 the back, and the head looks somewhat triangular. The 

 terminal serrations are less visible in palarica, being forced 

 under one edge, instead of being marginal. This shows 

 that the differences are due in some degree to a different 

 amount of twisting in mounting, caused by a difference 

 in form, not necessarily, however, that presented in the 

 preparations. 



The form of stygne with the nearest approach of clasp 

 form to that of palarica is var. pyrcnaica, but it is 

 distinctly stygne and not palarica. 



In palarica the side processes of the tegumen are 

 constantly though slightly longer than in stygne. Not- 

 withstanding the relative sizes of the insects, the clasps of 

 stygne and of palarica are of almost identical size, that 

 of stygne, var. bcjarensis, being longer. 



This is decidedly another character making bcjarensis 

 a variety of stygne, and palarica distinct. Contrary to 

 what perhaps one would expect, when geographical forms 

 differ in size, the size of the clasps differs also ; this is very 

 marked in tethiops where the large continental form has a 

 clasp large in proportion compared with the British form. 



* By dividing the chitinous ring in the central line between the 

 clasps, and opening it out on the slide, so that the two clasps are at 

 each end of the preparation. 



