214 [February, 



other genera of the NitidulidcB, as it only presents the appearance of 

 rather a small triangular excision on the lower part of the wing. 



In size the species range from J lin. to If lin. ; as a rule, how- 

 ever, they do not exceed 1 lin. The colour is usually black, sometimes 

 very shiny, sometimes dull or leaden ; several species have a bluish or 

 greenish (occasionally a bronze or purple) metallic lustre ; none, 

 however, of the British species are red or testaceous (like the Continental 

 If.fuscus), except a variety of M. ruji-pes, which is of a dark ferrugi- 

 nous colour ; a mahogany coloured tinge is sometimes present on the 

 purple varieties of M. csneus. 



As might be expected from the similarity of form, and in most 

 cases of colour, and also in consequence of the large number of species 

 (in the European catalogue there are over 100, of which w^e possess 

 more than 30), their identification is often very dilficult. Various 

 methods of subdividing them have been proposed, and different cha- 

 racters have been adopted by different authors. Erichson trusts 

 chiefly to the denticulation of the anterior tibise ; E-eitter makes a 

 great point of the straightness or emargination of the anterior margin 

 of the forehead, and also of the presence or absence of network or 

 cross striation between the punctures of the thorax and elytra ; while 

 Brisout lays great stress upon the characters of the under-side, par- 

 ticularly of the metasternum and the last abdominal segment bf the 

 males. All the differences that can be found in so obscure a genus 

 must be of great use. The species can be, as a rule, roughly separated 

 into groups by size, colour, and contour ; but the best determining 

 character appears to be the denticulation of the anterior tibise, and 

 the degree of punctuation and of cross-striation between the punc- 

 tures. The anterior tibiae present four or five distinct types of 

 serration or denticulation, and the punctuation and cross-striation 

 also varies considerably ; sometimes the latter takes the form of very 

 fine alutaceous network covering the whole body, sometimes of coarse 

 transverse scratches ; occasionally it is confined to the elytra and is 

 absent on the thorax ; and in one of our species {M. murinus) it is 

 peculiar to the scutellum ; in some cases only very slight traces are 

 visible, which are often so feeble that the interstices are, for purposes 

 of sub-division, conveniently regarded as quite smooth. In all cases 

 a compound microscope with at least a one-inch objective is required 

 for the examination of this* character. 



The characters of the under-side are, as has been said above, very 

 useful in many cases ; but it is a question whether they are always 

 quite constant, and they are, at all events, better regarded as secondary 



2i 

 tie 



3r 



