British Hymenoptera. 177 



notched in the middle, the tibiae and tarsi, yellow ; the 

 apices of the tibi^ inwardly black in the ? : these mark- 

 ings are very subject to variation. 



The character by which this species may be at once 

 distinguished is the form of the 2nd abdominal segment 

 beneath ; this, as in all the other species, has a transverse 

 sulcature situated at a little distance from its base, tra- 

 versed by numerous longitudinal costse ; from the level 

 of these costse the surface of the segment on the side 

 towards the apex rises suddenly at right angles to the 

 costae, the ventral surface again being at right angles, so 

 that the ventral surface and costse are parallel to each 

 other on different levels. This character is easily visible 

 if the insects be looked at sideways, and appears to be 

 always well maintained. Length 9 — 13 mm. 



A very common species, but generally confounded with 

 the following. 



The shape of the basal band alone is valueless, as 

 the same shape occurs in parietimis, and sometimes in 

 parietuin. 



7. Odynerus parietum, Linn. 



Linn., Syst. Nat., ed. x., vol. i., p. 572 ; Smith, Brit. 

 Foss. Hym., &c., p. 206. 



Very like the preceding, but rather more robust, and 

 so variable in coloration that no dependence can be 

 placed on that character ; the basal band of the abdomen, 

 however, as a rule, is angularly, not squarely, notched in 

 the centre. The form of the 2nd abdominal segment 

 beneath will separate it at once fi*om its allies ; the ven- 

 tral surface of the body, on the side of the costate 

 sulcature towards the apex, at its point of juncture with 

 it, is actually below the level of the costse instead of 

 rising up angularly to a higher level ; the ventral surface 

 is quite flat longitudinally, not convex as in all the follow- 

 ing species. Length 8 — 14 mm. 



Hah. Very common. 



8. Odynerus pictus, Curt. 



Curt., Brit. Ent. iii. 138 ; Smith, Brit. Foss. Hym., 

 &c., p. 209. 



This species differs from either of the preceding con- 

 siderably in colour, although some dark males oi parietum 



TRANS. ENT. SOC. 1882. — PART II. JULY.) 2 A 



