11)4 CHARLES ROBERTSON. 



of the mandible, its width taken on the line separating the base of 

 the mandible. 



The basal tooth of the claw in females of Megachilini is not ho- 

 mologous with the inner tooth of the claw in females of Trachusa 

 and Anthidiinse, as is shown by males of Ceratias, which have the 

 same basal tooth and cleft claws. 



Among the local Osmiini I do not find females with mandibles 

 distinctly quadridentate, except in Gnathosmia. The so-called 

 fourth tooth is a beveled angle between the two inner teeth and is 

 only seen when the mandibles are held in a certain position. None 

 of them have four external teeth like the female of Andronieus. 



The difference between my arrangement of the Coelioxyini and 

 Stelidini and that of recent authors seems to imply that I have a 

 different opinion as to their relationship. I hold that the arrange- 

 ment proposed by these authors does not give a correct statement of 

 their own views. There is a possibility, or probability, that Stelis 

 was developed from Dianthidium. In that case Stelis and Dianthid- 

 i a in are more closely related than Anthidium and Dianthidium, and 

 the groups should show that relationship. 



I had formed the opinion that Psithyrus citrinus 8m. was the male 

 of P. laboriosus F. before I happened to find a place where Walsh 

 has expressed the same view, in Proc. Ent. Soc, 3, 247, 1864. 



MEGACHlLlDiE. 

 SUBFAMILIES AND TRIBES. 



Females. 



Abdomen with white, yellow or red ornamentation ; claws cleft 3. 



Abdomen without ornaments, except pubescent bands. 



Pulvilli absent ; maxillary palpi 3-jointed ; segment 1 with a broad concavity ..2. 



Pulvilli present; claws simple ; scopa present 1. 



1. OSMIINJE. 



Metallic greenish, bluish or purplish ; maxillary palpi 5-jointed ; joint 1 of labial 

 palpi shorter than 2 ; abdomen at base with a slight concavity or sul- 

 cate OSMIINI. 



Black TRYPETINI. 



2. MEGACHILINI. 

 Scopa present; axilla? simple; pubescence of vertex, mesonotum and middle seg- 

 ments of abdomen more or less black MEGACHILINI. 



Scopa absent ; axillae produced into spines on each side of scutel. 



CCELIOXYINI. 



