252 [November, 



II. Eljfcra not alutaceous ; thorax at most with a basal depression. 



A. Hind tarsi shorter than tibiae, 1st joint subequal to the two following united 

 and not longer than 5th. 

 a. Thorax as long as bi'oad, distinctly narrowed in front, with a rather deep 



transverse impression in front of seutellum... O. nigrata,'^^vi:m. 

 aa. Thorax scarcely narrowed in front, without impression. 



b. Antennae more robust, usually entirely red-yellow, as are the legs ; 



average size larger 0. picina, Aube. 



bb. Antennae less robust, usually infuscate at apex ; femora infuscate ; 



average size smaller O. maura, Er. 



AA. Hind tarsi subequal to tibiae, 1st joint very long, subequal to the three 

 following joints united and plainly longer than 5th ; legs entirely 

 testaceous O. hihernica, Rye. 



The species included in the above table have little in common. 

 Eey (Brevipeunes, Aleocharaires, p. 419) proposes to separate 0. 

 incrassata as a subgenus (Mniusa), 0. nigrata as a second subgenus 

 {Gousya), and includes O. maura and picina in a third (Oct/usa). The 

 specimen of 0. hihernica from which the characters in the above table 

 were drawn was kindly lent to me by Mr. Tomlin, who tells me that 

 it has been compared with the original type. Presuming that it is 

 correctly named, it is evident that it cannot properly be included in 

 the genus Ocyusa as laid down by Key (Joe. et p. cit.), since the generic 

 characters of the posterior tarsi are : — " subelougate, less long than 

 the tibiae, with the first joint elongate, as long as the two following 

 united, subequal to the last." Rye described it originally as an 

 Aleochara in 1876 (Ent. Mo. Mag., xii, 175), but his description is 

 brief and quite inadequate. It is very desirable that the original 

 type should be re-described in detail. M. Charles Brisout appears to 

 have seen the insect, and compares it with nigrata, l'"'airm., but no 

 attention appears to have been given to the proportion of the tarsal 

 joints. 



It should be observed that although the antennae of O. picina 

 taken as a whole are much more robust than those of maura, the 

 penultimate joints of the latter are shorter and more transverse than 

 those of picina. The pale colour of the legs and antennae will usually 

 separate picina from maura, but occasional specimens of picina occur 

 in which these parts are nearly black ; an example of this form was 

 returned to me by M. Fauvel as picina. 



The unique British specimen of 0. nigrata was taken by Mr. 

 Claude Morley on June 2nd, 1900, in an unoccupied martin's hole in 

 the side of a sand pit at Levington, Suffolk, a place about half way 



