terminal segments of Aculeate Hymenoptera. 259 



the apical segments and armatures of the parasites, and 

 of the bees with whom they live : Megachile and Coelioxys, 

 Chalicodoma and Dioxys, Anthophora and Melecta, are 

 rather striking cases of this similarity. Throughout 

 the Anthopldla, so far as I have been able to examine 

 them, the hairs of the armature are branched or 

 plumose, and the 8th dorsal segment is simple, fit- 

 ting into the 7th, and of a horny submembranous 

 texture. 



Prosojns and Colletes. — In the Ohtusilingiics the 7th 

 and 8th ventral segments have most interesting modi- 

 fications. I have figured those of Prosopis in our 

 ' Transactions ' for 1882, PI. VI., and those of Colletes 

 are no less peculiar; the 7th is dilated at the apex 

 into one or two wing-like appendages, very variable 

 in form, according to the species ; the 8th has a cen- 

 tral apical process, hairy beneath at its apex ; the 

 armature in each genus is of a form peculiar to itself 

 {vide volume of our ' Transactions ' quoted above, 

 PI. VII.). 



Sphecodes and Halictus. — In these two genera the 

 7th and 8th ventral segments are nearly simple ; 

 they lie hidden by the 6th at the base of the arma- 

 ture as two corneous plates, generally slightly pro- 

 duced and rounded in the centre ; the armature has the 

 stipites short and somewhat curved, with a distinct 

 lacinia to each, the sagittae bent downwards at the apex ; 

 in both genera the form of armature affords excellent 

 specific characters {vide Trans. Ent. Soc. Lond., 1882, 

 PL VIII., IX.). 



Nomia. — In this most extraordinary genus the ventral 

 segments of the abdomen are flattened and somewhat 

 concave ; the 8th is pale and corneous, truncate in the 

 centre ; the 7th is emarginate, with the sides of the 

 emargination rounded and fringed with golden hairs ; 

 genital armature with a semicircular membranous apex 

 to each stipes; the sagittae raised and subtriangular 

 (see PI. XIII., fig. 18). 



Nomiuides. — In this little halictiform genus seven 

 ventral segments are visible, and the 8th lies close under 

 the armature, and is produced at the apex into an elon- 

 gate process ; the armature has the stipites elongate, 

 narrow and somewhat curved, the sagittse narrow and 

 nearly straight. 



Andrena.— In this genus the 7th ventral segment is 



