20 ADEPHAGA. 



A, bipustulatus, L. 

 luctuosus, Geoffr, 

 carbonarius, F, 

 V. abdominalis, Costa. 

 V, picipennis, Sahib. 



A. solieri, Aube. 

 tarsatus, Zett. 

 alpestris, Heer. 

 sexualis, Reiche. 

 V, kiesemvetteri, Seidl. 



I believe, however, that all these must be referred to ^1. bipustulatus, 

 which Dr. Sharp (Dytiscida^, Royal Dublin Society, 1880-1882, p. 532), 

 speaks of as " Species pervariabilis." 



As the question of variable sexual dimorphism is brought out 

 more strongly in this species than in almost any other, it is worth 

 while to quote Dr. Sharp's remarks on the difierent forms at length, as 

 they are not generally available to students (I.e. 553-554). 



"The variation found in this species is very complex and interesting. 

 The ordinary form may be considered to be that in which the female has 

 the surface duller than the male, and the longitudinal scratches finer, 

 denser and more oblique, the general form in both sexes being rather 

 regularly oval, the female, however, being generally just a little narrower 

 and more oblong than the male ; on examination under the compound 

 microscope, with a half-inch object-glass, it appears that the dulness of 

 the surface in the female is caused by minute scale-like reticulations, 

 which are not so deep in the male as in the other sex ; this form is that 

 universally found in temperate Europe, and I have it in my collection 

 as far East as Persia ; the size about 9-11 mm. long, 5-5| mm. broad ; 

 this may be called the ordinary or typical form. 



" In some of the warmer parts of Europe, there are found large 

 specimens in which the sculpture of the female is quite similar to that 

 of the male, which, as in the ordinary form just mentioned, consists of 

 very elongate, narrow meshes on the basal portion of the elytra ; this 

 may be called the South European variety. 



" In the highland districts of Britain, and in the Alps and Iceland, 

 the specimens become smaller, and of a narrower, more oblong and 

 depressed form, with the base of the thorax narrower than that of the 

 elytra, and the surface in the female excessively dull, so that the 

 disparity in the appearance of the sexes is very great ; but this form 

 (for females of which Aube proposed the name '■ Agabus solieri') is 

 connected with the common temperate European form by every shade 

 of dimorphic variation ; this may be called the dimorphic Alpine form. 



" In some localities in the Alps and Pyrenees there are found (I 

 believe always at a great elevation) specimens of elongate, narrow and 

 depressed forms, with very shining surface, the bculpture in the 

 female being similar to that of the male, and the meshes of the 



