184 MIMESA DAHLBOMI. 



of the tibiae also. Abdomen : the petiole linear, as long as the 

 first segment, and with a longitudinal carina above ; the ex- 

 treme base of the first segment black. 



The Male only differs in having the face more densely covered 

 with silvery pubescence, the legs more ferruginous, and the 

 abdomen less red at its base. 



A most abundant species, frequenting sandy districts ; it forms 

 large colonies, and furnishes its cells with a species of Tettigonia. 

 I have taken it at Hampstead, Erith, Luccomb Chine, Isle of 

 Wight, Yarmouth, Deal, Dover, and in Yorkshire. 



3. Mimesa Dahlbomi. 



M. atra ; abdominis petioli cannula dorsali lanceolata, distincte 



sulcata ; metathorace reticulato-rugoso. 



Mimesa unicolor, Dahlb. Hym. Europ. i. 1. 1. 



Psen unicolor, St. Farg. Hym. iii. 44. 4. 



Mimesa Dahlbomi, JVestn. Hym. Foss. Belg. 108. 2. 



Female. Length 4 lines. — Black ; head and thorax punctured 

 and shining ; a carina runs from the anterior stemma to a trans- 

 verse one which crosses at the insertion of the antennas ; the 

 face with a slight silvery pubescence ; the clypeus convex, its 

 anterior margin reflexed, with a notch in the middle. Thorax : 

 the scutellum smooth and shining ; the metathorax reticulated, 

 with a triangular space at its base obliquely coarsely striated ; 

 the wings subhyaline and iridescent, the nervures black, the 

 tegulae piceous; the claw-joint of the tarsi rufo-piceous, the 

 calcaria pale testaceous. Abdomen smooth, shining, and 

 covered beyond the basal segment with a fine silky white 

 pubescence ; the petiole narrowest towards its base, its lateral 

 margins raised, and having a raised elongate lanceolate carina 

 in the middle ; the apical segment compressed, above with an 

 elongate narrow angular space bordered on each side with a 

 sharp carina, the space enclosed flat, shining, and delicately 

 punctured. 



Although the differences between this species and Cemonus 

 unicolor are apparently not very great, still I agree with M. 

 Wesmael in considering them of specific value ; the difference 

 in the form and sculpture of the petiole, united with that of the 

 anal segment, are certainly greater than of a mere variety. The 

 only specimen I have seen is in the collection of British Hy- 

 menoptera in the British Museum ; it was formerly in that of 

 the late J. F. Stephens. 



